The social behaviour of the Common Buzzard...A. crucial aspect of my long-term study of the Common...

Acrucial aspect of my long-term study of the Common Buzzard Buteo buteoin Avon has been an attempt to unravel

the intricate nature of the species’ socialbehaviour, the results of which I present here.Other aspects of the study, which commenced in1980 and still continues, concern populationmonitoring, territory size and topography,breeding biology, nest-sites, and individual lifehistories, all gathered during over 18,000 hoursof fieldwork in my 75-km2 study plot, which liesjust west of Bristol. The area comprises amixture of woodland (mostly deciduous),grassland (meadows for cattle, horses andsheep) and some arable land, and rises from sealevel through wide, low-lying valleys to ridgesand plateaus up to about 180 m. There are manyvillages, as well as three large conurbationsadjacent to the area.

To gather information, I spent up to 1,200hours in the field each year, making between

seven and 28 visits per month, most visits lastingsome 3–8 hours. Visits were carried out in allmonths, although less frequently in winter. Earlyin the year, I check all territories for occupancyand then check nest-sites during March andApril. This is when most territorial behaviour isseen, although it can be observed at other times.When entering my study area, observationsoften start opportunistically; otherwise, I watcha single territory or go to a regular observationpoint (usually at low elevation), from where Ican monitor several territories. All observationsare noted, timed and attributed to the relevantpairs/territories. I aim to spend a minimum of25 minutes in a territory, in order to gainknowledge about conspicuousness, timebudgets, etc., as well as social and otherbehaviours.

At the start of my study, I was heavilydependent on the work already carried out byColin Tubbs (1974) and Douglas Weir and Nick

247© British Birds 102 • May 2009 • 247–273

The social behaviour ofthe Common Buzzard

Robin J. PrytherchABSTRACT During a long-term study of the Common Buzzard Buteo buteo inAvon, special emphasis was placed on social behaviour. This is shown to bemore complex than previously thought, with several new behaviours being

described. Furthermore, flight behaviours are shown to be distinctive for thetwo components of a resident population: territorial pairs and unpaired (non-

breeding), mostly one- to three-year-old birds. Buzzards defend their territoriesfrom intruding birds by using assertive postures initially. If necessary, further,more demonstrative, behaviours are directed at intruders. These behaviourshelp the birds to avoid fighting, but this does happen rarely. These and otherbehaviours serve to advertise the presence of a pair in a territory and are

important in pair-bonding. For breeding pairs, activity is normally restricted tothe territory, but some males engage in extra-territorial chases, which mayinvolve a form of reciprocal altruism. Some unpaired young birds defend

territories, but do not use the full repertoire of behaviours. Some aspects ofpair formation and relations within the family group are described, as well as

perched postures.The behaviour of juveniles is distinctive especially with regardto play, an activity that can be easily confused with adult behaviours. A few

exceptions are described. Suggestions for the origins of the displays are made.

Picozzi (1975), as well as the account given inVol. 2 of BWP (Cramp & Simmons 1980), basedlargely on the previous two studies. Soon Ibegan to realise the value of following individualbirds; by knowing their sex and/or age I waslearning so much more as they interacted withothers. It was also quickly apparent that thestudies mentioned above were far fromcomplete, as the social signals that the birds useto mark their territories are both complex andsubtle.

Common Buzzards (hereafter referred tosimply as ‘Buzzards’) vary greatly, not only intheir plumages, among individuals and ageclasses (see below), but to a lesser extent also interms of voice, ‘personality’ and shape. All ofthese features helped me to attribute particularbehaviours to individual birds and therefore tointerpret their purpose (I have identified asindividuals at least 60 birds during the studyperiod, by a mixture of plumage and othercharacters). In this paper, I describe first thevarious behaviours of both breeding (territorial)and non-breeding birds, and then describe theirfunction and how the behaviours relate to eachother. The social behaviour of territorial,breeding pairs is distinct from that of otherBuzzards and is crucial in interpreting theactivities of a group of two or more interactingbirds. Indeed, breeding and non-breeding birdscan be described as forming two components ofthe population.

Structure of the study populationIn my study area, all the breeding adults weresedentary, and defended their territoriesthroughout the year. They comprised the bulk ofthe population: 13 pairs in 1982, rising to 97pairs in 2008, with up to 107 juveniles by latesummer, in addition to non-breeders (a groupof unknown size, but probably fewer than 30).Most of the juveniles dispersed out of the area byearly autumn, but were replaced to some extentby juveniles from elsewhere. Many of thesejuveniles may subsequently have returned tosettle close to their natal area (Davis & Davis1992; Walls & Kenward 1998). Some juvenileswere initially sedentary (remaining in theirparents’ territory for much of their first year andrarely much longer) but most of them, andalmost all other non-breeders, were wanderersor ‘floaters’ – settling for a period (from a fewdays to several months) in locations free ofbreeding birds, but often adjacent to anoccupied territory. Many of these birds, likesome breeders, became very inconspicuous inmidsummer.

Before leaving the natal territory, juvenilescan be identified quite easily: they are toleratedby their parents, and also call distinctively whenin the territory. The call is usually a double ortriple ‘ki-ki’ or ‘pi-ya – pi-ya – pi-ya’ (but veryvariable), rather higher pitched and shrillerthan the better-known adult calls (which Iusually note as ‘ca-au’, but these are also highly

variable). The callsof juveniles arecommonly thoughtto denote hunger,but they also act toappease their parents;once fledged, juven-iles normally callonly when a parentis in view, and do soeven when the callerhas a full crop. Later,when making theirfirst flights beyondthe territory, theyoften call on theirreturn as they crossthe boundary, as ifto repress any attackfrom a parent (seealso below). Havingabandoned the natal

248 British Birds 102 • May 2009 • 247–273

The social behaviour of the Common Buzzard

132. Part of the study area in Avon: a view from Clevedon looking east-northeastalong the Gordano Valley (which forms the western third of the study area);

autumn 1994. It is an area of mixed woodland (mostly deciduous), damp meadows separated by ditches, and a small amount of arable land. Much of the flat area is within the Gordano Valley National Nature Reserve.

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territory, a juvenile will normally cease to call,unless attacked (by another Buzzard), when itmight squeal shrilly, until it occupies a territoryof its own two to three or more years later.

Once independent, juveniles did notappear to defend the areas in which theysettled and so these were not obviousterritories. In this they differed from many2nd-year (2Y) or older birds, which settled ina territory of their own. (Note that I use ‘birdyears’ rather than calendar-years todistinguish age classes, since the major moulttakes place from May/June in juveniles andfrom July/August in most adults, and lasts forat least four months.) Third-year and olderbirds could be referred to as adults, and wererarely unpaired. Intruders were chased out ofthese single-bird territories, but the fullrepertoire of behaviour (see below) was notused. Single-bird territories were usually heldfrom a few months to a year or more, until amate arrived or the bird moved on. Territorialpairs usually comprised two adults but, rarely,one of the pair was a juvenile or 2Y bird.These paired youngsters exhibited most of thebehaviours of older birds, but often in a lessdemonstrative way (particularly juveniles).Four of my territories have been occupied bythree adults (one male and two females ineach case; see below) and for three, five, sixand seven years, with the last three stillpresent in 2008.

I recorded theplumage details ofmany individualpaired birds andfound this a crucialaid to the study,enabling intruders(especially juveniles)to be identifiedquickly. Knowinghow to age birds inthe field was thereforeimportant. Plumageand structural differ-ences between ageclasses, together withbasic flight postures,are discussed in thispaper because of theirimportance in under-standing other behav-iours.

Age classes and ‘basic’ flight behaviourAdult Buzzards are distinguishable from juvenileand some 2Y birds in terms of plumagecharacters (see Appendix 1). Nonetheless,plumage variation is such that some juveniles(especially dark ones) can look very similar toolder birds. Furthermore, in silhouette, which isa typical view of a flying Buzzard, plumagefeatures are of limited value. There are, however,subtle structural differences and, moreimportantly, postural differences that help, andwhich lead neatly into social behaviour.

Almost all the territorial interactions are notbetween adjacent pairs, as might be expected,but between a pair and non-breeding (mostlyjuvenile), intruding birds. There are someexceptions, which I will describe later. A pair inits territory dominates all others that enter it(including its own young, some of which mayremain in the territory for variable periods afterfledging). The residents signal their status tointruders by a distinctive assertive bodylanguage. The intruders, regardless of their age,adopt passive postures. These are most oftendemonstrated in flight but equivalent signals aregiven by perched birds. Flapping flight, circle-and slope-soaring, sailing and gliding all havetheir distinctive forms (fig. 1). (When circle-and slope-soaring, birds ascend; when gliding,birds descend; but when sailing, birds driftabout maintaining roughly the same level. Suchsailing flights may include a few flaps or single

249British Birds 102 • May 2009 • 247–273


133. Part of the study area in Avon: the Gordano Valley, looking southeast towardsCadbury Camp (with the M5 viaduct just visible); September 2003.Woodland on the slopes gives way to improved or unimproved grasslands and wet meadows plus wooded hedgerows.The majority of the wet meadows form part of the

Gordano Valley NNR or reserves of the Avon Wildlife Trust.

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circles. When slope-soaring, birds may ‘hang’ onan updraft or hover.)

In flapping flight, adults beat their wingsrapidly on stiff wings. This may be interspersedwith circle-soaring, slope-soaring or sailing,when the wings will be held in a slight dihedral(raised from the body to the tips and forming ashallow ‘V’). In a close territorial encounter, thewings are held more stiffly, although thedifference can be quite subtle and varies with thestrength of uplift and, particularly, betweenindividuals. These are assertive postures.However, when an adult is moving casuallythrough the territory at low level, flapping flightmay be more relaxed; in particular, the wings areheld in a flatter, more relaxed, slightly rakedposture (wings slightly tucked in towards thebody with the hand pointing slightly back; seefig. 1) when gliding but also, occasionally, whensoaring and sailing (see also Combridge 2000).Intruding birds almost always adopt passive,

relaxed, flight postures. Flapping is less rigid,slower and with a rather paddle-like effect.When soaring or gliding, a juvenile intruderholds its wings less stiffly and in a slightly moreraked posture compared with an adult. Second-year or older intruders also adopt passivepostures, but because of their more adult-likeproportions (see Appendix 1) these are lessobvious.

If an intruder is not threatened by adults,these postures are often not so obvious,especially for distant birds, when it is difficult tobe sure of the status of some individuals. Ingeneral, though, when young birds are involvedin a territorial encounter, their relaxed, passivewing action is different from the adults’assertive, stiff-winged, rapid-flapping flight. So,in such an encounter, the intruding bird wouldseem to be signalling the passive nature of itspresence, while the adult is making it equallyclear to the intruder that it should move on.



Fig. 1. Basic flight behaviour and two age classes of the Common Buzzard Buteo buteo.Top right, Juvenile/1Y (a)above an adult (b) as in circling or sailing. Note the slimmer wings and relatively longer tail of the juvenile, and the lack of an obvious dark subterminal bar along the trailing edge of the wings and tail, although in some dark

youngsters this can be hard to see. Rely then on the different proportions, which are obvious even in silhouette.Below these are the equivalent views from the front.The juvenile (c), above the adult (d), tends to hold the wings

flatter, but may vary somewhat, especially when alone, raising the wings in a shallow V but always looking morerakish. Centre and top left, juvenile (e) above adult (f) in the gliding posture.The juvenile looks slimmer and

more rakish as in the small image below right (g).Top centre, head-on view of a gliding bird (h), although oftenwings are raised a little. Below left, an adult (i) in the rarer passive, flat-winged, circle/sail attitude.The other

small image, upper left (j), shows the usual going-away glide. See text for further explanations.

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Should this basic signallingfail to have effect, the adulthas a choice of otherbehaviours to draw upon toreinforce its message.

Pairs mostly restrict theirterritorial activity to theconfines of their own terri-tory, but temporarily theymay become wind-driftedover the adjacent part oftheir neighbours’ territory.There are exceptions, whichI will describe below. Inreality, the observer will often recognise territo-rial activity part way through an encounter, orlose track of the action before it is over. It isonly through regular watching over longperiods that it is possible to stitch together thevarious elements of the behaviour.

Territorial behavioursBehaviours are described below in an idealisedorder from the moment that a perched adultfirst spots an intruder, through a chase sequenceto evict it, then the basic displays as the adultreturns to a perch. This is followed bydescriptions of variations and other displaysthat might occur as more intruders arrive andcomplicate the situation. Finally, I describe someother perched postures, the behaviour ofjuveniles and, briefly, expand on the exceptionsreferred to above.

Although territories are defended through-out the year, there is a distinct peak of activity inspring, from mid March to mid April, and atrough in summer, when birds can be veryinconspicuous. Territorial behaviour increasesagain in the autumn as the juveniles disperse,but during the depths of winter the birds spendmost of their time hunting and feeding, andintruders are chased out promptly (or almostignored if they pass over quickly). Some displaysmay be used, especially display stoops (seebelow). From February onwards, displayingbirds are seen more frequently. These timingsare only approximate and are weather-dependent. Fine days with a mixture ofsunshine, cloud cover and moderate winds seemto be best for observing display. In winter,activity can be seen at almost any time of the dayand occasionally in poor weather. Otherwise,most activity takes place between mid morningand mid afternoon.



Fig. 2. Assertive bow. Moving into a horizontal posture, the adult lowers itshead, sleeking the head feathers, with the base of the upper neck raised (right),

sometimes with the secondaries flared slightly. Invariably, the bird calls (left),looking up at the intruder that has stimulated the display.The posture is

usually held for a few seconds, rarely longer, before the bird relaxes or flies off.

In the accounts that follow, ‘adult’ will referto a territory-holder, ‘intruder’ to any otherBuzzard not holding a breeding territory. Thelatter comprise mostly juveniles but also 2Ys anda few older birds in adult plumage. In this paperI introduce a new terminology for some of thebehaviours so, where necessary and for the sakeof clarity, I will also give the terms used in BWPin parentheses.

Conspicuous perching and assertive bow(perch-and-call display, high perching)Buzzards spend the majority of their timeperched, in trees and bushes, on fences, poles,etc., as well as on the ground. Here they ‘rest’ andcarry out routine behaviour such as preening,as well as using the perch to hunt from.Throughout the year, but most obviously inwinter and spring, when foliage is absent, adultswill perch conspicuously. This will often be highup, typically in a tree (preferably on a deadbough) or on a pylon. Such a position will givethe bird a good view over its territory. To thecasual observer the bird may appear to be quiterelaxed, but this is deceptive; an adult Buzzard isalways alert.

From such a location, an intruder enteringthe territory is readily spotted. If this shouldhappen, the adult will call ‘ca-au’ (the familiarand widely known call, sometimes written as‘pei-eu’ or other variants) and may adopt theassertive bow (fig. 2). This serves as a warning tothe intruder: ‘get out or further action willfollow’. The intensity of this behaviour variesgreatly, but usually the bird adopts an almosthorizontal stance with the head lowered andhead feathers sleeked. This produces a slightlyhump-like effect at the base of the neck/top ofthe back. At its least intense just the head islowered slightly, whereas at the other extreme,

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with body level, the wings are drooped (see pp.263–264 and figs. 16 & 17, perched postures).The posture may be held for a few secondsbefore the bird relaxes or flies off, calling. If theintruder has turned and is heading out of theterritory, or is high and moving fast across theterritory, the adult relaxes. If the intruderremains in the territory and shows no sign ofleaving, the adult will take flight, often calling.

On other occasions, an adult may remainperched while calling, sometimes with its mateperched nearby, also calling. One canoccasionally also hear a bird from aneighbouring pair calling. The purpose of thiscalling is not entirely clear, unless to draw theattention of an intruder to the resident. But itoften becomes clear that an intruder is perchedwithin view (but unseen by a human observer),as eventually one of the adults flies off into coverto emerge quickly chasing an intruder.

When a feeding bird is approached byanother, it will mantle the prey and the head issometimes sleeked and lowered, as in theassertive bow.

Engage and escortThere is urgency in the initial, rapid flapping butthe adult (male or female, but usually theformer) soon circle-soars assertively, calling,rising fast towards the intruder. As the adultapproaches the intruder, the differences in flightposture are most obvious. As they circle up, theintruder higher, circling passively, they will



Fig. 3. Adult (below) engages juvenile in circling flight,the latter holding its wings passively in a flattish,

slightly raked posture.The adult is holding its wingsassertively, somewhat stiffly and raised in a shallow V.The adult starts much lower than the intruding bird.

Fig. 4. Adult below/left, escorting a juvenile intruderout of its territory. Note that the adult retains abroader-winged appearance in the glide posture.The adult will normally turn back as soon as it

reaches the edge of its territory.

usually be wind-drifted to the edge of theterritory (fig. 3). At this point, the adult willturn, usually to glide back down to perch as the intruder continues beyond the territory.Alternatively, at some point the intruder maystop circling to glide, heading into the wind. Theadult will then follow the intruder, usuallysomewhat lower, or alternatively the adult maytake the lead. During this glide the intruder willusually adopt a slightly more raked wing posturethan the adult, which adopts a fuller-wingedgliding posture (fig. 4). Again, once the intruderleaves the territory the adult will turn,sometimes to circle and then glide back down.At times, the birds will rise to over 1,370 m andregularly to over 900 m. On one occasion, Iwatched an adult male and intruder disappearmomentarily into the cloud base before glidingout, whereupon the male, having reached theedge of his territory, dived down directly to hisnesting wood, just 17 m above sea level. Thecloud base recorded on that day, 14th May 1997,by the Bristol Weather Centre, was between1,295 m and 1,370 m. At this height, fromalmost sea level, the birds appear tiny to thehuman eye (and still rather small through 10xbinoculars). This suggests that the territory‘ceiling’ is not a specific height above theground, but is related to prevailing weatherconditions.

This is the least aggressive form of territorialencounter, but is usually the prelude to any ofthe following behaviours.

Attack and chaseAlmost invariably, an intruder may appear toshow some reluctance to leave a territory. In this

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case the adult may decide to press home anattack. To do so it will have to ascend to be levelwith, or above, the intruder. The adult usuallycircle-soars assertively, occasionally flapping upstrongly. It can then fly powerfully at theintruder, causing it to flee – initially by flappingand then, as the adult gets closer, by divingdown, followed closely by the adult (fig. 5). Theythen split apart quickly, swooping up again,when another dive might follow. Usually,though, the adult will chase after the intruder,the latter occasionally weaving from side to sideor down to avoid contact until it leaves theterritory. During such an attack the adult willoften lower its talons. This is an aggressive signal(as indicated below). At any time the adult’smate may circle up assertively, calling ‘ca-au’,sometimes joining its mate in a two-prongedattack on the intruder. During close encountersthe adult will usually lash out with its talons, theintruder responding likewise. On very rareoccasions the adult and intruder may ‘locktalons’, whereupon they spiral down, flapping



Fig. 5. Attack and chase. An adult (top right) isattacking a juvenile intruder (top left) that, once the

adult gets close, will dive down to avoid contact.The adult dives after the intruder as it continues

the attack, but they split apart. Invariably, the adult chases the intruder and the action may be

repeated several times before the latter is expelled from the territory.

Adults will sometimes dive from a much higher position whenthey spot an intruder below,which will then take similar

avoiding action.

wildly. Such a fall varies in length but the birdsusually break apart after a few seconds and thechase continues. Exceptionally, birds that ‘locktalons’ may fall to the ground, where I have seenthem remain locked, the adult on top of theintruder, until the latter manages to escape. It ison such occasions that birds may be damaged,or even killed. I know of at least one juvenile andan adult male that were almost certainly killedby another Buzzard, and a female that strained aleg when fighting with a juvenile. The juvenileescaped with a few broken feathers and thefemale’s leg appeared to have recovered withinthree days.

It is interesting that males seem to attacksome intruders with much more energy thanothers. Whether these are persistent intruders ordominant individuals is difficult to tell.Certainly, 2Y or older intruders are usually dealtwith aggressively and promptly.

Frequently but not invariably, the male takesthe lead in an attack and chase, and the femalemay remain perched. If she does take flight, shemay rise up, as mentioned above, or circle lowfor a while before dropping down, with loweredtalons, to a perch where, on settling in aconspicuous position, she wing-waves (seebelow). Otherwise she lands rather heavily,briefly adopting the assertive bow.

Once the intruder (or intruders, since thereare often two or three, sometimes more) has leftthe territory, the adult (or pair) may circle or sailabout before dropping down to perch. It is justas likely, however, that the adult will performseveral display stoops (see below) after anyencounter with an intruder.

Wing-wavingThis display is given on a conspicuous perch (seeabove), which might also be an old nest (of theirown or that of a corvid), most often by a femalewhen her mate is involved in aerial activity with

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intruders. The perch will be approached fromnearby cover or from above, if in flight. Talonsare lowered during the approach and on settling,usually rather heavily, the head is lowered (as inthe assertive bow), the wings remain partly openand are flapped rapidly (but not raised high) forseveral seconds, the tail fanned (fig. 6). The birdwill call loudly (‘ca-au’ or a more abrupt,repeated, ‘cau, cau, cau...’), cocking its head up tocheck on the action above, and then slowlysubside into a normal posture. The display isalso rarely given on the arrival of an intruder



Fig. 6. Wing-waving is given from a conspicuousperch, usually by a female. The waving action is

quite rapid, which, together with the calling,makes the bird obvious to an intruder.

Fig. 7. Display stooping. A schematic outline of several versions of this variable display. Having seen off an intruder, the adult glides over the territory (a) then suddenly closes its wings (sometimes after rising slightly) anddives down (b). It soon pulls up and after rising, at the point of stall (c), it continues into the second stoop of fourit performs before gliding off to settle near its mate. Alternatively, after two stoops it changes direction, performs

two more rather shallow stoops before dropping down to settle near its mate. Otherwise it may circle up (d)then sail off over the territory, or display dive down to settle close to its mate (e).The number and intensity

of the stoops can vary greatly even within a series. See also figs. 8 and 9.

into a territory, before any aerial activity hastaken place. This conspicuous behaviour servesto warn an intruder that it is in an occupiedterritory or to reinforce the message during anencounter between its mate and an intruder.(See also pp. 263–264 for other perchedpostures.) The ‘heavy landing’ mentioned aboveis distinct from the normal method of landingwhere the bird approaches from below andsweeps up with wings fully spread to settlegently on its chosen perch. In a heavy landing,the bird approaches the perch at the same levelor from slightly above, before settling.

Display stooping, display dive (roller-coasterflight, sky dance display flight, undulating flightand deep dive flight)The stooping display is perhaps the one mostfamiliar to the casual Buzzard watcher and is themost frequently performed of all the aerialdisplays. It is, however, highly variable, owing to different intensities of action and strength of wind. It also occurs in two basic forms. Thefirst serves mainly as the culmination to a terri-torial encounter (above), affirming territory

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occupation, which is dealt with here; the other,aggressive form is dealt with later.

The action is distinctive and conspicuous,occurring from c. 1,300 m down to treetop level(fig. 7). Having expelled the intruder, the adult

may glide or circle over the territory, then atsome point, usually when heading into the wind,the display stoops may start (fig. 8): the bird willeither (a) suddenly close its wings and dive; or(b) rise up slightly, tail usually closed, then



Fig. 8. One display stoop to reveal the detail.The full explanation is given in the text.The degree of closure of the wings at (a) is highly variable (both within and between series) and some display stoops will be so

shallow that the wings will not close more than shown at (c).The display dive posture is shown in (f).

Fig. 9. The aggressive form of the display stoop varies from the normal form in two ways. (The bird at (c) matches that in fig. 8c.) Firstly, at (d), the bird flaps its wings wildly a couple of times and calls, with talons

lowered.Then, at the end of the stoop, as it levels out, it lowers its talons and may continue calling as it sails off (g).The bird at bottom right is a front view of the same action as at bottom left.

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suddenly close its wings and dive down. Theclosed wings are usually held slightly out at thecarpal joint, often with the alula feathersprotruding. The tail is often fanned initially, butsoon closes. During the dive the bird gathersspeed, the angle of descent being very variable(see below). After only one or a few seconds, thewings open (c) as the bird then swings throughthe base of the stoop and rises up. In the finalpart of the rise, the wings will be fully extended,tail closed, and may end with the bird travellingnear vertically upwards. When almost stalled(d), the bird will close its wings again as it peaksand continues into the second display stoop. Thebird may perform just one stoop, although aseries is more typical. A series of 3–5 is commonbut this can be extended up to 12 and rarely toover 20. The display usually ends after point (c),at the base of the stoop, as the bird levels off toglide or circle, or to drop down to a perch if ithas ended near ground level. The displaying birdwill often call, usually just before or at point (d).During such high-level displays, it is oftendifficult to be sure when the calls are made, ifindeed they can be heard at all.

At the display’s least intensive, the angle ofdive and rise and the extent of closure of thewings are considerably less, so that the birdappears to undulate gently. Such mild displaysare usually composed of only two or three linkedstoops. During more intensive displays, the diveand rise can be marked, as the bird performs adeep ‘U’, wings well open at the base but closingjust before the peak, the bird twisting over todive, more or less at the stall point (d).Occasionally the bird changes direction here,rather than continue down in the samedirection. To achieve this, the bird may brieflythrow out one wing in order to turn to the newcourse. Display stooping is initiated into the windand the bird can use the wind to subtly changethe direction of each stoop so that it ends updisplaying downwind. Between the mild andmore intensive forms there is much variation,with stoops deepening and wings more closedwith increasing intensity of the display.

The most intensive form of display stoopingdiffers from the others towards the end of therise, after a deep dive. Instead of closing thewings just before or at the stall, the bird keepsthem closed as it rises vertically, carried by themomentum created during the dive (e). Onlywhen close to stalling does it peak to continueinto another stoop. Even within a series, the

display stoops will rarely all be of the sameintensity, starting at low intensity anddeveloping into higher intensity or vice versa.Each series is usually distinct but may be brokenby a long glide between two stoops within theseries. Many series end at low level with the birddisappearing into the canopy. Occasionally, thefinal stoop converts into a display dive (seebelow), which may take the displaying bird 100 m or more down into woodland or to aconspicuous perch (see above). Otherwise thedisplaying bird will simply revert to gliding,sailing or circling. Generally, a series of displaystoops will cause the displaying bird to descendgradually, but over a slope with a strong updraftthe displaying bird may rise as much as itdescends during the dive, and thus maintainheight. If both members of a pair continue tocircle or sail after a territorial encounter, theymay both display stoop down together, eitherone taking the lead with the other following.

The displaying bird demonstrates a thrillingcombination of grace and tremendous élan. Itgives the impression of great fitness, and thismessage is presumably transmitted to its mateand to any other Buzzards in the vicinity. It mustbe remembered that this display occurs after anyintruding birds have left the territory, eventhough it/they may still be visible.

Display stoops which occur during aterritorial encounter take a different, aggressiveform (fig. 9). This is much as above except thatat point (d), at the top of the rise, the bird makesa couple of exaggerated flaps with talonslowered before dropping into the next stoop.The displaying bird, however, rarely performsmore than two or three stoops in a series.During the flaps the wings are raised high,exposing the undersides. This is probably a briefform of display flapping (see below). Asmentioned, aggressive display stooping occursonly in the presence of intruding birds(commonly when there are several) and thedisplayer (or pair) usually seems to be highlyexcited, giving repeated ‘ca-au’ calls. At the endof the display, the bird may also level out fromthe dive with lowered talons (g), sometimes evendropping down to a perch to wing-wave (seeabove). Talon lowering is a vital action, whichdistinguishes aggressive forms of severalbehaviours.

A display dive (fig. 8f) commences just like adisplay stoop but then the dive, with almostclosed wings, alulas protruding, continues down



at high speed in a straight line to a perch.Although usually performed as the final dive ofa series of display stoops, it also occurs on itsown, after a bird has been up high for sometime, and for no apparent reason, but alsoduring a territorial encounter. If a female is up,but below her mate, who is engaged with one ormore intruders, she might suddenly display divedown and leave her mate to deal with thetrouble.

Display flapping (deep wing-beat flight,slow-flapping display-flight)This behaviour is performed at the start of, orduring a territorial encounter. Used almostexclusively by the male, this distinctive flight canoccur at treetop height or high in the sky. Thebird will suddenly interrupt circling or glidingwith a series of 4–7 very pronounced wingbeats,with the wings raised higher than normalbetween each powerful, downward flap. Thebird is propelled rapidly, often making excited‘ca-au’ calls; the tail is usually closed (fig. 10).Display flapping will often be performed soonafter an intruder is spotted over, or approaching,the territory. The male (or female) will call as itleaves its perch, soon display flapping one orseveral times before circling up assertively. Hemay then perform display flaps again at a higherlevel, particularly if his mate suddenly appearsin flight below. Alternatively, the male mayalready be high in the sky ‘waiting’, as he watchesother distant pairs engaged in territorial activity.Then, invariably when an intruder makes anapproach, he will suddenly display flap severaltimes.

This display serves to draw the attention ofapproaching intruders to the presence of adultsin a territory. The male usually gives theimpression of being highly excited, but theaction is very variable. Sometimes the flightseems rather wavering and the actual flapping

action may be less intense, at times appearingalmost lackadaisical.

Display flapping is occasionally combinedwith other behaviours, particularly the displaybank (see below), which causes a rapid change ofdirection. I have occasionally seen a femaledisplay flapping, but only at low level andusually at low intensity. During its first year in aterritory, the male will sometimes display flapfrequently when his mate is nearby.

This behaviour is demonstrated when I entersome territories to inspect nests. Birds willwatch me, display flap and then (very rarely)dive at me, with much calling (a sure sign, at theappropriate time, that the nest has chicks).

Display bank, and sailing and banking displayAlthough Buzzards will sometimes tilt overwhen circle-soaring in a strong wind, this isnever as marked as in a display bank. In thisaction, the Buzzard turns sharply with wingsheld stiffly, the bird tilted over so that the wingsare held almost vertically and usually flattened(fig. 11). The tail is usually closed. Furthermore,this action is not associated with normalcircling. It is used mainly in conjunction withother displays, especially display flapping(above). A bird will also sometimes display bankat the ‘top’ of a display stoop in order to changedirection. Rarely, birds display bank at the end ofeach of a series of shallow downward dives,which is part of the sailing and banking display.This display usually includes frequent displayflaps. The impression given is of a more dashingversion of display stooping, but when the birdbanks the wings are swept up a little, rather thanheld stiffly. This is an extraordinarily gracefuland swift flying display, which also seems toreflect anxiety but to a higher degree. It isinteresting that this display is associated withmales when they are new in a territory and musttherefore feel the pressure from both adjacent



Fig. 10. Display flapping is performed at the start of, or during, a territorial encounter.This shows the wings atthe highest and lowest points of the flap in its most intense form. At lower intensity the wings are raised less.

The display is often accompanied by calls.

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established pairs and intruders. I also have theimpression that some young males have notquite resolved the distinctive nature of thevarious parts of the separate displays (i.e. displayflapping, banking and stooping) and they getthem mixed up in their excitement.

Assertive flight postureFollowing a territorial encounter, an adult maycircle and sail about high in the sky, oftenbecause it can see some action in an adjacentterritory. Then if an intruder approaches, theadult will sometimes call and adopt the assertiveflight posture (if it does not display flap) as soonas the intruder enters the territory (fig. 12). Thisaction is subtle and quite brief. The wings areheld stiffly and usually flat (though sometimesraised slightly), with all feathers fanned to givemaximum spread; the tail may be fanned orclosed. The head is lowered slightly with thefeathers sleeked and a small hump appearsbetween the neck and the back. This is,therefore, an aerial version of the assertive bowand seems to have the same function of awarning. The posture is held for just a fewseconds before the adult relaxes to circle or sailassertively. The intruder may then fly on, out ofthe territory, and the episode is quickly over.Occasionally, however, the intruder may



approach the adult,which will adopt theassertive flight postureagain; this mightdevelop into theaggressive form of thisdisplay, which simplyinvolves the addition oftalon lowering (figs. 12& 13a). The adult maythen suddenly flickover to attack theintruder with itstalons, which remainlowered for severalseconds (fig. 13b), butthen a chase mightfollow. On suchoccasions, the intruderdoes sometimes seemto be ‘attracted’ to theadult and gives thestrong impression ofmaking a mock attack,despite the obvious

threatening signals. Both sexes will adopt thisposture, sometimes as a pair.

Dive-on, turn-over displayThis behaviour involves the pair and occurs intwo forms: passive and aggressive. Typically, aftera territorial encounter and as the pair sailoverhead, the male positions himself above andbehind his mate. He then dives fast towards herand on arrival over her drops his talons as sheturns over and raises hers. The talons rarely, ifever, touch. The female immediately rightsherself and both retract their talons to sail orglide on as before (fig. 14). The action may berepeated once or twice soon after. The femalewill occasionally roll over (through 360°) duringthis display. This is the passive form of thedisplay and may serve to maintain the pair bond(see below). The pair will, however, perform amodified aggressive form of this display duringa territorial encounter when several birds areinvolved (i.e. at a territory boundary when bothadjacent pairs and several intruders aretogether). During the melee of dive-chasing,circling and so on, the male may dive on his mateas in the passive form but after the turn over thetalons remain lowered. The lowered talonsindicate the aggressive intent and at the sametime signal that they are a pair. This display can

Fig. 11. The display bank display is always used in conjunction with display flappingand more rarely with display stooping. Note that the wings are often held flat (butsometimes swept up by the force of the turn) with the tail closed. It is not a part

of normal circling.

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be difficult to pick out among the dive-chasesthat are also occurring during a mass encounter,especially as (rarely) the male from one territorymay dive at the female from another. The pointto note is that an intruder flees when attacked(even if, momentarily, it turns and flicks up itstalons), but a territorial female does not. Suchsituations involving several birds can be veryconfusing, even to the practised eye.

In late summer and autumn, when a juvenileis flying over the natal territory, it may approacha parent in flight and ‘mob’ it. The parent (maleor female) may then quickly flick over in aneffort to fend off their pestering offspring. Thejuvenile will usually give its distinctive callduring this action, but nevertheless it can bemistaken for the full dive-on, turn-over displayof the pair if the observer is not familiar with the



Fig. 12. Assertive flight posture as seen from below (right) with, above it, the view from the side to show thelowered and sleeked head. All the flight feathers are spread to the maximum extent, usually with the wings

flattened, although sometimes the tail remains closed. The aggressive form of the display is shown below left;the lowered talons are stimulated by the closeness of the intruder (above left). See also fig. 13.

Fig. 13. The aggressive form of the assertive flight posture is indicated by the lowered talons, as in (a), where an intruding juvenile dives slightly hesitantly down to an adult male, with its mate circling below and beyond,which also lowers its talons. This is followed (b) by the male flipping over to attack the intruder, which fleesinstantly.This is often followed by a chase.The roles of the sexes may be reversed. These actions could be

mistaken for the dive-on, turn-over display of a pair (see fig. 14).

a b

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Fig. 14. The dive-on, turn-over display is performed by a pair, often after a territorial encounter. The male divestowards the female from behind (a), usually at a fairly shallow angle. As he arrives over her (b), he lowers his

talons as she turns over and raises hers, but usually avoiding contact.The male sails on (c), perhaps turning backto repeat the procedure once or twice more. An aggressive form is used when intruders are still in the territory.

In this case the talons remain lowered (d). Sometimes, as here, the male has combined the action with theassertive flight posture as revealed by his lowered and sleeked head.

Fig. 15. An example of how various displays can be combined. In this case, the pair is gliding down after aterritorial encounter with two intruders (which have just left the territory). The male suddenly display banked (a)

and display flapped (b), then performed one display stoop (c) before display diving (d) down to the female and they performed the dive-on, turn-over display (e). Note that the talons are tucked away since the

intruders are no longer present. The pair continued on to settle in one of their nest woods (f).

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status of the birds involved.The dive-on, turn-over display will rarely

culminate a series of other displays after a periodof territorial activity (fig. 15).

CopulationFrom early March (rarely earlier), Buzzard pairscopulate frequently and continue to do so untilafter the egg-laying period (all the pairs in mystudy area, with few exceptions, appear toproduce eggs each year). This behaviour peaksin early April, when the pair may perform morethan two copulations per hour. The action isconspicuous and can occur anywhere in theterritory – high in a tree, on an electricity pylon,on the ground, etc. Even within the woodlandcanopy, the flashing of the white under-primaries of the male as he balances on thefemale show through the branches and twigs,especially on a sunny day. Many copulationsoccur when intruders are present, orimmediately after they are expelled from theterritory. Typically, when territorial action ishigh in the sky and the female has droppeddown to a perch, the male will suddenly close hiswings and dive or glide down to her, eventhough the intruder(s) may not have left theterritory. He usually arrives with talons slightlylowered, directly onto the female’s back (shemay or may not have solicited by lowering herhead). The male makes a rather quiet call, ‘eez-ka’, during copulation, which is rarely audible tohuman observers. He then flies off from hismate’s back to circle or sail up again, or percheither next to her or nearby. On other occasions,when the intruder is much lower, the male willbreak off the chase, drop down to the female,copulate, then fly off, with loud calling, after theintruder to continue the chase. I suggest that thebirds are using the conspicuous behaviour ofcopulation for a secondary purpose, to signalclearly to an intruder that here is a pair onterritory.

Extra-territorial chases and flightsGenerally, a pair confines its territorial activitieswithin the territory. There are occasionalexceptions when the male leaves his territory –usually when engaged in a prolonged, high-levelchase that extends across adjacent territories.The other pairs below call excitedly, sometimesflapping around at low level, but do not usuallyget involved further. Eventually, the chasingmale gives up (he may be up to 2 km away at this

stage, although usually less) and returns to histerritory. I once saw a neighbouring male ‘escort’the intruding male back to his territory. Theyflew close together, with the occasional mildjostle but no obvious aggression. On arrivingback at the territory, the male will often displaystoop several times (occasionally calling) as hedrops down to perch.

Such behaviour is clearly rare, but that ithappens at all is interesting, and appears to be aform of reciprocal altruism. There is normallylittle or no territorial interaction betweenadjacent pairs, and they clearly ‘know’ theirneighbours and other pairs beyond. It is possiblethat neighbours of a male involved in an extra-territorial chase will recognise what ishappening. Furthermore, since most dispersingjuveniles settle close to their natal territories(occasionally adjacent) (Davis & Davis 1992),they could be closely related. ‘Helping’neighbours on rare occasions may not,therefore, be a disadvantage, as long as theneighbours reciprocate.

Although even more unusual, a pair maymake an extra-territorial flight. They may circleup, drift out of their territory, then glide on awayfrom it, passing over several other territories toeventually circle again, rising very high beforeslowly gliding/sailing back. On their return theymay display stoop/dive down in several stoops toperch. During the ‘outing’, other territoryoccupiers seem to ignore them and if an adultdoes circle up to them there is no obviousterritorial response. It is impossible to hearwhether the pairs call at each other, but I thinkthat it is likely.

Single-bird and three-bird territoriesIn my study population there have occasionallybeen single birds holding a small territory. Thebirds are usually in their second or third year,rarely fully adult. When defending theirterritories they restrict their behaviour mainly toassertive bows, engage and escort and wing-waving, accompanied by calls. The actions are allrather low-key. A crippled female, whichdefended a territory for over five years until herdeath, never attracted a mate. She also display-stooped and was generally more conspicuous.

Three-bird territories are created when ajuvenile stays with its parents for over a year.Even a young juvenile will occasionally help tochase out an intruder, but not usually on itsown. As it gets older it tends to keep a low



profile, but will occasionally join its parents insome territorial behaviour. Very rarely, a youngfemale will stay on into adulthood, remainingwith her parents. I have recorded only one caseof polygyny in my study (which involved onemale defending two territories, with two females– a mother and daughter – in one and a singlefemale in the other).

Pair formationGenerally, a new (or replacement) pair ofBuzzards appears on territory without obvioussigns of pair formation. This might seemsurprising for a long-lived species whichfrequently has pair bonds that last up to 20years. I have, however, seen pair formation insingle-bird territories. The incumbent has beena male, obviously highly excited/anxious by thearrival of an adult female. He demonstrates bycalling as he display flaps wildly near the female,then settles to watch her. It could be that he issomewhat nervous, and torn between chasingher off and accepting her. The female appearstotally unconcerned, or may fly to the male anddisplace him from his perch – females usuallydominate males. Then the male may fly fasttowards the female and attempt to displace her;rather than be displaced she merely flicks herwings or ignores him. Alternatively, the malemay veer away just as he arrives at the female, orbrake to a hover before gliding away. In somecases, the male may fly so hard at the female thatshe is forced to jump up to present her talons(collapsing back onto the branches). The maleusually makes two or three of these flights infairly quick succession. One single male maderather timid approaches to a new female, wholeft within a week. Then another female arrivedand he immediately behaved more aggressivelytowards her; she stayed. It appears that thefemale is judging the aggressiveness of the male,which may relate to the male’s ability as ahunter; that will be confirmed during the mate-feeding behaviour prior to breeding (see below).

The similarity of this action to the dive-on,turn-over display by established pairs is obvious,and (the latter) probably serves to reinforce theoriginal pair bond. The display flapping indicatesconfusion on the male’s part between mateattraction and intruder expulsion. Thisbehaviour is also difficult for humans tointerpret, especially when there is no knowledgeof the status of the birds involved. Furthermore,once the pair seems to have settled, one partner

will often fly to perch next to its mate, causingthe other to fly to another perch (each time thebirds will briefly adopt the assertive bow onsettling). This may happen several times andindicates a low level of residual anxiety.Established pairs often perch close together, fullyrelaxed.

Relations within the family groupAfter the young have fledged, they usually spendabout six weeks with their parents beforedispersing. At the end of this period, and forlonger if one or more of the juveniles remain inthe territory, confusion is possible as thejuveniles interact with their parents. Thehunger/appeasement calling of juveniles can beso incessant that the adult will fly away to ‘hide’from its noisy offspring, but is otherwise quitequiet and not always easily heard. The adultsnormally do not fly at a juvenile to flush it away,although I have rarely seen this. Typically,though, the juvenile will fly at its parent, whichit displaces. This might be repeated if the adultdoes not move far. This action is identical to thatused by new pairs, when the female mightrepeatedly displace the male, and to that byyoung birds feeding in a large group when theyoccasionally displace each other (see below).

From time to time (especially in winter andspring), the pair will often perch very close toeach other, occasionally almost touching, butregularly about 30 cm apart. The second toarrive usually briefly adopts the assertive bow asit lands close to its mate; this is more common innew pairs, and probably reflects a mildlyaggressive (or even nervous) reaction. I haveseen an old female settle thus next to herdaughter (by now a full adult, sharing the samemate) but, while in the assertive bow, sheinstantly turned her head through 90° for acouple of seconds before relaxing. My impressionwas that this had a ‘switching-off ’ effect,cancelling any unintended aggressive message.When apart, the pair will occasionally call quietlyto each other – ‘cau, cau...’ – and at times thisseems to be a contact call associated with food.Females will call like this from the nest.

Mate feedingDuring the month or so before eggs are laid,male Buzzards start to provide food for theirmate (Hinde 1985). The term ‘courtshipfeeding’, which often refers to this behaviour, ismisleading for Buzzards as the behaviour



continues throughout incubation and the earlypart of chick-rearing. Thereafter, the behaviourchanges slightly and the male often takes thefood directly to the nest, although he does notusually feed the chicks.

Perched posturesTwo perched postures, the assertive bow andwing-waving, have already been mentioned, butBuzzards assume a variety of postures whenperched (fig. 16). If the birds are hunting in theopen, their plumage is more or less sleeked andthe body vertical, or tilted forward if facing into

a strong breeze (fig. 16e). Otherwise, whenrelaxed, they sit in a squat, hunched posture(figs. 16a,d) with (in cold weather) the bodyfeathers fluffed out, covering the legs and mostof the feet (fig. 16a). If a bird becomes aware ofa hidden disturbance nearby, its first reaction isto ‘stand up’, sleeking the plumage (fig. 16b),looking intently towards the noise. If nothingtranspires, the bird quickly relaxes. It may havespotted possible prey, in which case it maystretch up as high as possible (fig. 16c), ratherthan move. If an intruder suddenly appears, theadult will instantly call and adopt the assertive



Fig. 16. Various perched postures. These show relaxed adults (a) and (d), the former in cold weather, with most of the legs and feet hidden in the plumage. In (b), the adult has become more alert. The other alert

adult (c) has spotted possible prey (or an intruder), which it is straining to see beyond a nearby obstruction.The juvenile at (e) is sleeked in a leaning posture owing to a strong wind, and the one at (f) is sleeked on

the approach of a territorial adult.

Fig. 17. Perched postures during aggressive interactions with intruders. In (a), an adult runs in the assertivebow at a large juvenile female, which flapped off to avoid physical contact. More extreme versions of the assertive bow are also shown, with the secondaries flared (b), and the secondaries flared even more (c),

causing the primaries to lower, and the head is lowered further, rarely almost to the ground.

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bow (fig. 2), and then fly towards the intruder, asdescribed earlier. Similarly, an intruder perchedin a territory will sleek its plumage as soon as itsees the approaching adult, before flying off (fig.16f).

Groups of juveniles with some 2Y or olderbirds will gather on bare, tilled land in ‘no-man’s-land’ between territories to feed, particularly onearthworms Lumbricus (see also below). Theadjacent adults will also be feeding in such areasand checking any straying intruders. An adultwill fly at such an intruder to displace it; if thelatter does not move well away, the adult may run(fig. 17a) or sidle up to it adopting the assertivebow in an extreme form. In this case, the adultturns side-on to the intruder and flares itssecondaries (fig. 17b). The amount of flaring isvariable and has the effect of ‘pushing’ theprimaries down so that they touch the ground(fig. 17c; ‘wing-drag walk’ in BWP), with thehead lowered even further. Usually, only the wingfacing the intruder is flared, although both wingsmay be flared at times. This has the effect ofmaking the adult look larger and moreintimidating. As a final resort, the adult mightlunge at the intruder. When the pressure of alarge number of feeding intruders is too great,the pair has to give way to them (I have seen upto 60 spread over c. 10 ha), although feedingpairs usually keep a clear area around them. Insuch cases, an abundant food supply andpressure from other Buzzards has forced theterritory holders to relax their defensivebehaviour. Interestingly, the large gatherings of

young birds dispersed in all directions at duskand did not seem to be involved in a communalroost. It appears that these young birds arealready showing signs of being solitary, whichtypifies the adults’ behaviour (see also Glutz vonBlotzheim et al. 1971).

Behaviour of independent juvenilesHaving left their natal territory in their firstautumn, juveniles seldom settle in defendedterritories, but wander over a larger area. Theymay stay in an area where there is an abundantfood supply, congregating with other juveniles.Here, they will feed in close proximity (within20 m) without interacting. The most frequentinteraction is when one flies low to displaceanother from its feeding place. The latter maynot submit but turn to engage the new arrival byjumping up and resettling, then rushing at theother, whereupon they lock talons or stand closetogether and adopt angel postures (Weir &Picozzi 1975), one ‘fully spread’ (pseudo-dominant), the other either ‘half ’ or ‘fallen’(submissive) (fig. 18). Head feathers aresometimes raised and, although I have neverbeen sure of seeing the crest raised purposefully(Weir & Picozzi 1975), I have seen the sameeffect caused by wind blowing the feathers up.

These scuffles usually break up quickly. I haveonly ever seen juveniles perform these angelpostures, never an adult. On one occasion, whena juvenile walked within a few metres of a 2Y ona fence post, the latter dropped onto thejuvenile, which flattened into a fallen angel (fig.



Fig. 18. The angel postures used by juveniles. Initially (a), having rushed together, wings are opened and the birds may jump up, or one attacks the other, they lock talons and one falls into the fallen angel (b).

A 2Y attacks a juvenile, which immediately adopted the fallen angel posture, with the 2Y looking on (c).These episodes are normally fairly brief.

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18c). Another juvenile, attacked by an adultfemale on the edge of a territory, refused tomove off. The female approached again, in anassertive bow; the juvenile adopted a half angeland stepped backwards, whereupon the femalewalked away. The angel postures apparentlyserve to appease an attacker and are submissive– but with a hierarchy from least submissive(full) to total submission (fallen).

PlayJuveniles often gather in small groups (up toabout seven) in flight, often above a hilly bluffforming a boundary between two territories,and engage in apparent play activities (fig. 19).They circle, dive on others, chase, settle anddisplace (actions sometimes reciprocated), oftenweaving through the treetops at great speed.They will also fly at and grab a cone or smalltwig (items that may be mistaken for prey byobservers), which is carried aloft and dropped,followed by a zigzagging chase to recapture it,unless another bird intercepts it. These activitiesappear to be ‘without purpose’ and to representthe classic play behaviour exhibited by the youngof many birds and mammals (Immelman 1985);this appears not to have been recorded in theBuzzard before. Such episodes may last from

several minutes to around half an hour. If thegroup strays too far into a territory, one of theadults (usually the male) will approach, oftenadopting an assertive flight posture, and evendive at or chase the nearest bird, but I have neverseen an adult fully engage in play. Eventually, thejuveniles circle up, glide or sail off in ones ortwos in various directions and the episode isover. When hunting on the ground, a juvenilewill occasionally rush at something (e.g. a clodof earth, a piece of vegetation), pounce on it andthen jump up, drop it, jump up again, tossingthe object about and clearly playing with it. Aftera few seconds, the bird will return to huntingproper.

ExceptionsInteractions between pairsAs emphasised above, during social behaviour it is intruding non-breeders that stimulateterritorial adults to rise up and evict them. Manynew pairs that take up a territory adjacent to oneor more established pairs experience no conflictwith the older birds. On some occasions,however, the male from the older territory willfly over the new territory and engage with one ofthe new birds, even diving at it. Both will circleassertively and/or adopt the assertive flight



Fig. 19. Play behaviour of juveniles. This involves much chasing, including when one has a play object (a).Birds will dive at branch tips to detach items such as cones (b), which may be dropped and dived after (c).

On the ground any small, loose object may be dashed at, dislodged or thrown up (d). Up to seven birds were involved in the flight episodes observed in this study, which mostly happened at treetop level and

sometimes lasted over half an hour.

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posture. Normally this activity will diminishquickly and within a few weeks the pairs more orless ignore each other.

Aggressive interactions between well-established pairs occur only rarely. On oneoccasion, I watched a female sail into herneighbours’ territory where she was attacked bythe male, after which she was soon back over herown territory. The neighbours had young chicksstill branching (when the chicks wander fromthe nest but before they are capable of flight)and this may have caused the unusuallyaggressive reaction.

Persistent adult intrudersA similar activity might involve an adultintruder that attacks and chases a resident adult(i.e. male on male). This could result in theintruder killing the resident and thus effect amate change. These ‘battles’ can last,intermittently, for two weeks or more beforebeing resolved, but are rarely observed, at leastin my study.

Adult-like behaviour of juvenilesTowards the end of their first year, somejuveniles may (rarely) show signs of adult-likebehaviour. I have seen one dive downaggressively, with talons lowered and toesspread, among a small group of other youngstersand an adult. It quickly assumed the expectedpassive glide and relaxed flapping as the adultsailed assertively towards it. On anotheroccasion, a lone juvenile had been using thecorner of a grass field to feed in for a week or so.When another juvenile arrived, the first birdadopted the assertive posture, with secondariesflared. The first bird was simply showing itsdominance over the second, which soon flew off.Such events probably happen fairly frequently.

Summary of territorial flight behavioursHaving described in detail all the variousdisplays and postures, this summary is intendedto help underline the relationships betweenthem and make their purpose clearer. This willbe a hypothetical description since in realitymost actions may involve only some of thebehaviours, and there is great variation inindividual behaviours both within and betweenepisodes.

Once a perched adult spots an intruder flyingover, it may call ‘ca-au’ as it adopts the assertivebow. It may remain perched if the intruder

passes over quickly, otherwise (usually) it takesflight with rapid, stiff-winged beats, sometimesdisplay flapping. The adult, usually the male,then circles assertively up to the intruder, whichcircles above in a more relaxed passive posture. Ifthe intruder is persistent, the adult may chase itand dive at it aggressively before circlingresumes. Once the intruder glides off, the adultwill follow it, somewhat below and behind, untilthe former leaves the territory. The adult willthen turn back, dropping down to a perch in asteep glide, or it may display stoop a few times.

Alternatively, the adult may stay aloft,sailing about or circling. If another intruderapproaches, the adult may display flap and call‘ca-au’. If the intruder enters the territory, theadult might adopt the assertive flight posture,perhaps calling again. If the intruder approachesthe adult, by sailing towards it, or by divingdown to it, the adult will briefly lower its talonsinto the aggressive form of the assertive flightposture, even rolling to direct its talons towardsthe intruder. By now the adult’s mate (thefemale) may have appeared, circling up to theaction, perhaps briefly display flapping andcalling. It may also adopt the assertive flightposture, aggressively if necessary. One or bothmembers of the pair may then chase theintruder out of the territory. The pair mightthen, after a period of circling, perform the dive-on, turn-over display two or three times inmoderately quick succession before circlingagain.

One or both adults might then display stoopdown to the trees, or they may glide to meet yetmore intruders, perhaps at the territoryboundary where neighbours are engaged withthem. As they join in the circling melee, whichcould now involve eight or more birds, thepair(s) will engage in display flapping, andaggressive forms of assertive flight posture,display stooping and dive on, turn overs,seemingly throwing themselves about in the skywith abandon. The female might dive down,with talons dangling, to settle conspicuously,from where she calls and wing-waves. Once thebirds have risen to well over 1,000 m, quitesuddenly the sky empties as the intruders glideoff fast and the adults drop down to the trees.This might be by one fast display dive or a seriesof display stoops, the pair doing so close to eachother, but rarely synchronised.

All these behaviours are concerned withterritory defence (and advertisement): the birds



are signalling ‘get out’ and, once the intrudershave gone, the display stooping and dive on, turnovers reinforce the pair bond.

DiscussionIn this section, I refer to previous key studies inabbreviated form: BWP (Cramp & Simmons1980), GvB et al. (Glutz von Blotzheim et al.1971), Tubbs (Tubbs 1974) and W&P (Weir &Picozzi 1975). My study reveals new informationabout the social behaviour of Buzzards, some ofwhich conflicts with previous work. In trying toexplain these differences, it is worth consideringseveral general points. I have put in far moreeffort (see p. 247) than the other studies. Eventhough Tubbs’s main study lasted ten years, hehad sparse information to work from, and thesame applies to W&P, whose study lasted onlythree years. These and other accounts failed torecognise that any resident population ofBuzzards comprises two components (territorialbreeding adults and unpaired birds), as I havedescribed, which reveals not only separate basicflight postures for the two age classes, but thatthe social behaviour which determines territorymarking is confined to the older (breedingadult) component. Similarly, the significance ofthe distinction between ‘passive’ (or submissive)and ‘assertive’ (or aggressive) behaviours wasnot fully realised. Some of these facts have beenimplied by other studies (see BWP and GvB etal.) but not stated specifically.

Behaviours including conspicuous perchingand assertive bow, engage and escort/chase,display flapping, and display stooping and divehave been described in earlier accounts but notalways clearly understood. I have chosen newnames for some of the behaviours for the sake ofsimplicity. Wing-waving is described clearly inBWP but not identified as a discrete behaviour.Behaviours that have not been described beforeare assertive flight posture, display banking,banking and sailing display, and dive on, turnover, as well as the aggressive forms of displaystooping, assertive flight posture and dive on, turnover.

The catalyst for all of the loud calling andsubsequent territorial activity by adult birds isan intruder. The progression of behaviours fromthe first sighting of an intruder through to itsdeparture from the territory has not previouslybeen described (see summary above). Most ofthis behaviour is effectively a highlysophisticated form of signalling designed to

avoid overt aggression. Significant physicalcontact is unusual and will often occur onlyduring an attack (involving talon-locking,culminating as a fight on the ground). The angelpostures exhibited by juveniles are primarilyconcerned with determining hierarchy, althoughdamage might occur.

Without this vital background knowledge,many behaviours can be easily misinterpreted; Icertainly did so early in my study. This isdemonstrated by the widespread misunder-standing of the most basic of observations, thatwhen two Buzzards circle together it is the malethat circles above (or ‘leads’) the female (quotedby or suggested by all the above accounts). Thismay be so if it is the pair which is circling, but itis more likely to be an intruding juvenile (maleor female) above an adult male. The impressionof smallness is, of course, due to the slightlysmaller size and slimmer proportions of theyoung bird. This will be emphasised if the adultfemale is escorting a young intruder.

There are many suggestions in the keyliterature that behaviours are related to‘courtship’; this is misleading, in my view,especially where it concerns attracting a mate.This aspect of social behaviour in the Buzzardseems to be very perfunctory. Pairing appears totake place very quickly and once a pair is settledin a territory the two birds are usually togetherfor life. There may be some changes in the firstyear, although these are rare and I havewitnessed only one ‘divorce’. Should one partnerdie, replacement can be rapid, often within aweek, but may take several months. Butsuddenly the new bird is there and behaving as ifit had been in the territory for years.

The calling contests described by Tubbs asbetween pairs are, in my view, always directed atan intruder, even if it is not visible to the humanobserver. One pair might start the calling andalert the other pair to a ‘problem’, perhaps anintruding bird (or even a human observer) ontheir common border or in a narrow strip of‘no-man’s-land’.

It is clear to me that the dive-on, turn-overdisplay (not recorded by other observers) hasbeen mistaken for an adult chasing an intruder.Certainly it can be difficult to distinguish thisbehaviour if it occurs in a large group high inthe sky involved in all sorts of activities.Similarly, mock dives by a juvenile on an adultthat is in the assertive flight posture can beconstrued as an adult diving on a juvenile (if one



is not familiar with the detail of the behaviour)and may also account for W&P’s ‘wing-touching’, which I have otherwise never seen.

I have never seen adults use angel postureswhen involved in antagonistic encounters. Thishas only ever involved juvenile and 2Y birds, andeven the latter do not get fully involved. W&P, inusing a captive bird, may well have observedactions that may be less likely in the wild.Continental writers (see BWP, GvB et al.) mayhave seen interactions involving adults (i.e.where migrants and residents mix in winter),but this is not clear. GvB et al. described a birdmaking ‘pecking movements towards theground’ and attributed it to ‘displacement-activity’. I have never seen this but I suspect thatthe action described may have been an extremeform of the assertive bow.

Tubbs discussed the likely vertical dimensionof a Buzzard territory and estimated that theceiling would be c. 160 m in the New Forest(Hampshire) and c. 250 m above the valleyfloors in south-central Wales. These estimatesare far too low and, as suggested above, theceiling height is probably determined by weatherconditions. I have seen birds above 1,400 m,level with the cloud base, and they may well gohigher on fine, cloudless days.

I have described a wide selection ofbehaviours, which also vary in intensity withextraordinary subtlety. Buzzards can be highlyaggressive, a trait necessary for catching largeprey, but also useful in the defence of territories.However, attacking another Buzzard has to be alast resort and many of the displays and otherbehaviours seem designed to avoid this whilestill deterring intruders. The appearance of anintruding Buzzard stimulates most of thebehaviours described and, without suchstimulus, pairs spend hours below canopy leveland dispense with rising high into the sky. Insummer (with nests to attend to), and even inwinter, they can be very inconspicuous.

Origins of the displaysWhy has this species developed such a widerepertoire of social signals? The fact thatterritorial adults will go to great lengths to evictintruders without resorting to physical contactis clearly significant. The evolution of suchsignalling is complex but it may be related tobasic autonomic actions such as intentionmovements, flight (hunting and casual) andfeeding movements (Krebs & Davies 1981).

When unchallenged by intruders, adultBuzzards will fly about their territory in arelaxed mode, with the wings often slightlyraked and sometimes held quite flat or, moreusually, slightly raised at the tips; flaps will alsobe rather relaxed. Most commonly though, theadults are flying because an intruder has beenspotted, in which case they switch to theassertive modes of flight. Wings are held morestiffly, the dihedral is more obvious, and flapsare more rapid. In other words, this is anexaggerated form of the normal flight. Thiscertainly makes them look bigger, with the flightfeathers spread to maximum effect. These arethe most basic signals, together with calls, thatadults use to indicate that they are in a territory.Intruders acknowledge the submissive nature oftheir flight by maintaining relaxed postures,which also helps to make them look smaller;large birds dominate smaller ones.

Intention to take flight is not always obvious,but birds will momentarily adopt a horizontalposture at take-off. Frequently, the most obviousintention movement is to defecate. Thisnaturally puts the bird in a horizontal postureand, after a short delay, it flies (if it does notrelax). This appears to be the root of the assertivebow. The lowering of the head, with sleekedhead plumage, seems to be a modification toamplify the action. This latter action is also animportant part of the aerial form of the display,the assertive flight posture.

Display flapping is almost identical to theflapping flight used in a low-level hunting flighttowards prey. For the display, the flight ismodified to give a slightly wavering effect andcan be made more conspicuous with theaddition of display banks, which are modifiedfrom a part of normal circling flight. Thebanking action is steeper than in normalcircling, the tail is closed and the turn isrestricted to about 180°.

Display stooping seems to be based on twoseparate actions that have been combined,namely a hunting stoop and normal landing ona raised perch. Hunting stoops are rarely asimpressive as the display version, whichemphasises (in the most intense forms) theclosed wings (briefly held with the carpal areapushed out, sometimes with alulas spread, andwing-tips over the tail) and speed of the stoop. Ifa hunting stoop is aborted near the ground, thebird sweeps up on spread wings and this ismimicked in the display stoop at the end of each



downward dive section. But this also mimics theupward sweep to a normal landing on a raisedperch, all the more so since the bird often closesits wings as it lands deftly, almost at the momentof stall. In the most intense form of the displaystoop, in the final rising section of the stoop, thebird closes its wings before reaching the stallpoint and peaks before stooping again. In thisway, the Buzzard has neatly combined twocommonly used parts of routine behaviour tocreate one of its most impressive displays.Display dives are also derived from the huntingstoop.

The two parts of the dive-on, turn-overdisplay appear to have evolved from differentbut related behaviours. The dive on by the maleseems to be a simple modification of the chasingaction of an adult on an intruder. The turn overby the female is a barely altered action normallyused by both sexes when they are mobbed byconspecifics, corvids or other raptors. In bothcases, however, the talons appear to be clenched,hiding the claws. The talon lowering that occursbriefly is a normal part of the separate actions(except that then the claws may be exposed) andsignals their aggressive origins. However, in thiscase, between members of a pair, the male issignalling his aggressiveness to the female andshe her dominance, as she does not flee. Themutual confidence signalled by this action couldalso indicate compatibility in the pair.

In the aggressive forms of display stoopingand diving, assertive flight posture and dive on,turn over the talons are lowered; the birds arethus signalling with their lethal weapons!Although talons are also lowered briefly duringaerial attacks by adults on intruders, in theaggressive displays the talon lowering is moreprolonged. All these actions must have theirorigins in a hunting strike, when the talons areusually lowered and thrust forward at the lastmoment before the capture of prey.

Wing-waving also has an aggressive element,revealed by the flying bird as it approaches aperch with lowered talons and then lands heavily(without the usual sweep up from below), as ifonto prey. The wing-waving which then followsis probably a modification of mantling – thepartly spread wing posture used when a feedingbird is approached by another intent on stealingthe prey. The mantling bird may flap its partly

open wings as it lurches at an interloper. It ispossible that this flapping action has beenexaggerated to produce this very conspicuousdisplay.

The full angel posture adopted by fightingjuveniles is exactly the same as the posture at themoment of ‘capture’ of a prey item on theground, especially where the bird seems not tobe sure whether the item is in its talons, as itlooks down intently. This seems to indicate aconflict of aggression (needed to catch the prey)with anxiety (or fear) of the possible retaliationof the prey (which must happen often). Whentwo fighting birds make contact (usually talon totalon), one soon relaxes slightly or evencollapses on its back to indicate submission.This seems to be enough to ‘switch off ’ thedominant individual and the birds soonseparate, the submissive bird fleeing.

Acknowledgments

This paper is dedicated to my late friend Ken (K. E. L.)Simmons, who showed me how much more fulfillingbirdwatching can be by taking an interest in what birds do,that is, watching their behaviour. Without his example andinterest, I would not be writing these words now. I havemany other people to thank, simply for encouraging meand taking an interest in my studies. More specifically, Ithank Mike Wilson for providing me with a translation ofthe relevant parts from Glutz von Blotzheim et al., and IanNewton for his encouragement and for reading andcommenting on a draft of this paper that resulted in manyimprovements.

References

Combridge, P. 2000. Common Buzzard soaring on flatwings. Brit. Birds 93: 644.

Cramp, S., & Simmons, K. E. L. (eds.) 1980. The Birds of theWestern Palearctic. Vol. 2. OUP, Oxford.

Davis, P. E., & Davis, J. E. 1992. Dispersal and age of firstbreeding of Buzzards in Central Wales. Brit. Birds 85:578–587.

Glutz von Blotzheim, U. N., Bauer, K. M., & Bezzel, E. 1971.Handbuch der Vögel Mitteleuropas.Vol. 4. AkademischeVerlagsgesellschaft, Frankfurt am Main.

Hinde, R. A. 1985. ‘Courtship feeding.’ In: Campbell, B., &Lack, E. (eds.), A Dictionary of Birds. Poyser, Calton.

Immelman, K. 1985. ‘Development of behaviour.’ In:Campbell, B., & Lack, E. (eds.), A Dictionary of Birds.Poyser, Calton.

Krebs, J. R., & Davies, N. B. 1981. An Introduction toBehavioural Ecology. Blackwell, Oxford.

Tubbs, C. R. 1974. The Buzzard. David & Charles,Newton Abbot.

Walls, S. S., & Kenward, R. E. 1998. Movements of radio-tagged Buzzards Buteo buteo in early life. Ibis 140:561–568.

Weir, D., & Picozzi, N. 1975. Aspects of social behaviour inthe Buzzard. Brit. Birds 68: 125–141.



Robin J. Prytherch, 23 Caledonia Place, Clifton, Bristol BS8 4DL

This deals with the features that are mosthelpful; these are not full descriptions. Thedarkest adults have a dark breast with, below thepale crescent (which may be almost absent onthe darkest birds), heavily barred belly and flanks.The barring can be fine or bold and often theflanks – and even the belly – appear uniformlydark at a distance. From these darkest birdsthere is a cline through almost limitless variationto the palest, which may have just a few streakson the sides of the breast, but the belly andflanks will usually show some fine or faintbarring. Intermediate individuals (the majority)will always show barring on the belly and flanksbut the breast may be blotchy, speckled, streakedor a mix of these. The eyes are dark. In flight, abroad, dark subterminal bar is visible along thetrailing edge of the secondaries and innerprimaries, clearly demarcated from the other,much finer barring on the underside of theflight feathers. This bar is also apparent on theupperwing of most individuals but is usuallydifficult to see in normal viewing. The tail issimilarly marked but the width of thesubterminal bar is more variable.

Buzzards fledge with a distinctive juvenile/1Yplumage, different from that which, after 2–3years, they will retain, through moults, for therest of their lives. The remiges are narrower andshorter than those of adults. This gives juvenilesa narrower-winged, relatively longer-tailedappearance than adults. Juvenile plumage ispaler than the corresponding adult plumage (ofwhichever morph), but nonetheless someindividuals can be very dark. The eyes are palegrey or pale yellow and can be difficult to see ona distant bird, giving a rather plain-facedappearance. The scapulars and wing-coverts aretipped pale (whitish or buff); the greater-coverttips usually show up as a pale bar and this maybe a useful ageing feature on both perched andflying birds (note that some adults show thisfeature, but on them it is less obvious). Theunderparts are streaked, rarely with some ratherblotchy barring on the flanks and ‘trousers’(upper leg feathers). The dark subterminal baron the tail is usually the same width as the otherbars, occasionally slightly wider. The equivalentbar on the secondaries is more variable in widthbut rarely well demarcated, so that the darktrailing edge fades into the rest of the

underwing. On the inner primaries, the bar isnarrower and not well demarcated – this is thebest section of the wing to concentrate on for abird that is difficult to age. Overall, juvenileslook immaculate, although some flight feathersmay get broken as time passes. By the end oftheir first year, often during May, they will starttheir first moult, usually indicated by a missinginner primary or outer secondary. Buzzardsnever undergo a complete moult (i.e. all thefeathers replaced at one time), so after this pointall birds will show a plumage with feathers ofmixed ages.

Second-year birds retain many juvenilefeathers, which gradually become extremelybleached and faded. As new median and lessercoverts appear, they are strikingly darker and areoften obvious on perched birds. Many of theinner greater coverts are retained and these oftencontrast markedly with replaced, outer feathers,which are longer and darker. All the innerprimaries are usually replaced and the newfeathers have a broad, dark subterminal bar ofadult type, distinctively different from that of ajuvenile. Because the feathers are longer, theyalso change the proportions of the wing-tip. Theretained outermost (‘fingered’) primaries areshort and worn; the effect is to make the wing-tip look broader and more square-ended. Someof the outer secondaries are renewed but most ofthe inner ones are retained. This gives an unevenappearance to the trailing edge, with the innerwing ‘pinched in’. The 2Y wing is thereforedistinctive, although not always completelyobvious! Initially, the eyes of most 2Ys will showsome paleness but the vast majority have darkeyes by the next summer, when they are twoyears old.

Virtually all third-year birds are inseparablefrom adults. During the second moult, almostall the retained juvenile feathers will be renewed.The odd feather retained for a second year maybe invisible, but occasionally the outermostprimaries and/or the outer tail feathers will beold, and obvious with an appropriate view of thebird. Exceptionally, an individual may retain afew juvenile median wing-coverts and an oddgreater covert, which stand out as very paleagainst the new, darker feathers. In all thesebirds, though, the trailing edge of the wing willbe neat (barring any damaged feathers).



Appendix 1. Key to identifying age classes of nominate Common Buzzard Buteo b. buteo



136. This Common Buzzard Buteo buteo, observed in the study area in January 2006, is a tricky individualto age, since the barred flanks and dark eye suggest full adult plumage. But note the two pale, shorter,juvenile greater coverts, which, together with two ages of feather in the remainder of the greater-

covert tract, confirm that this bird is a 3Y (i.e. is in its fourth calendar-year).

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134. This 2Y Common Buzzard Buteo buteo(photographed in the study area in November 2005)shows a bewildering mix of juvenile and new feathersfollowing its first moult. The mix of older (shorter)

and newer (darker and longer) feathers is mostobvious in the greater coverts and secondaries.

There is a mix of old and new feathers on the body,but especially on the median and lesser coverts. Theeye is exceptionally pale for a 2Y (although this may

be partly caused by the low sun).This is a particularlyscruffy individual, and many are much neater – see

plate 135, right.The chestnut colour on the undertail-coverts is staining from the soil, via the talons.

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135. The age of this 2Y Common Buzzard Buteo buteo (photographed in the study area in October

2008) is revealed by the four shorter, paler,greater coverts. Some pale juvenile lesser coverts

also remain, but this bird is much smarter than many2Ys. This bird was hunting, and is therefore sleeked,

thus hiding the secondaries. As yet, no barring is visible on the crescent.

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137. This is a dark adult Common Buzzard Buteo buteo, yet the pale crescent below the

breast is still present; Latvia, April 2004.

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138 & 139. Common Buzzard Buteo buteo, juvenile (above) and adult (below); both Sweden, September 2005.These two together make a fine comparison.The most conspicuous difference is the dark trailing edge to theflight feathers, being bolder and more sharply delineated on the adult.This juvenile is typical but on some this

feature may be even less obvious and on others more so.The subterminal tail bar is more obvious on this juvenile than usual.

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140 & 141. Common Buzzard Buteo buteo, juvenile (above, Finland, November 2005) and adult (below, Sweden,September 2004). From above, the most obvious difference between these individuals is in the tail, with the dark

subterminal bar present on the adult, but not on the juvenile. Unusually, the juvenile’s greater coverts are notclearly marked with pale buff tips.

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The social behaviour of the Common Buzzard...A. crucial aspect of my long-term study of the Common...

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