Sound recording and the birdwatcher P. J. Sellar INTRODUCTION

Since the previous review of bird sound recording in this journal (Simms and Wade 1953) a vast amount of progress has been achieved both in the field and in the laboratory. Indeed, so many discs and cassettes have been published that some would-be re­cordists on the brink of taking up the pursuit are deterred by the feeling that most of the work has already been done, with all the species including the rarities recorded, and that there is nothing left to do—at least nothing readily accessible. They imagine that the domain of bird sound study is now the laboratory and the sound-proofed box.

In reality the majority of recordings available for scientific study today leave much to be desired in terms of accurate and detailed documentation. After all, most published recordings have been made to satisfy an aesthetic desire to achieve a pleasing result for the listener. The real paucity of well-documented recordings of, for example, courtship and alarm calls has only recently come to light during the preparation of the voice section in the fordicoming The Birds of the Western Palearctic. In some cases the sex (and even the species) has been wrongly identified, and only rarely is in­formation available on the bird's behaviour. Particular difficulty has been found in matching recordings with descriptions in the literature of vocal activity in courtship display. Behaviour specialists seldom turn out to be sound recordists. The aim of this review is to set this matter right and to indicate the opportunities which lie in wait for the field ornithologist with only modest equipment and no recording experience at his command: awaiting his first recording efforts there is a great deal of stimulating work no farther away than his own back garden, opportunism being regarded as the primary requisite, quality of recording as of secondary importance. A new approach is needed, culminating in the scientifically docu­mented recording for which the birdwatcher has to assume a dual role as observer/recordist.

This sounds dull expressed in so many words but those I know who have taken up sound recording with this approach all confirm that, far from proving a distraction, it has brought new life to the art of basic birdwatching. Many aspects of behaviour which have previously escaped one's attention quite suddenly assume fresh interest. In sound recording there is often a need to lie in wait, to stand still for a while, and this can never be a bad thing in field ornithology.

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OPPORTUNITIES FOR INVESTIGATION

In suggesting possible subjects for investigation let us consider those most urgently in need of attention. They conveniently divide between two kinds of activity: the permanent set-up in the garden and the opportunist work in the field. In terms of worthwhile return on time and energy expended, the garden wins hands down. Getting to know the vocal repertoire and associated behaviour of a few common species can have one totally absorbed to the ex­clusion of all other activities. The vocabulary of the Chaffinch Fringilla coelebs has been extensively studied by Marler (1956) and his recordings have been deposited in the Library of Natural Sounds at Cornell. The process of song learning in the same species has been studied by Thorpe (1958), and all the recordings he made during this intensive study are now available for further research at the British Library of Wildlife Sounds (BLOWS). The House Sparrow Passer domesticus has been treated by Summers-Smith (1955) but a collection of sound recordings to complement his work would be a really worthwhile assignment. There has been remarkably little published study, bio-acoustically speaking, of the Song Thrush Turdus philomelos, the Dunnock Prunella nodularis or, indeed, the Robin Erithacus rubecula.

With the help of colour-ringing there is plenty of scope for study­ing the inheritance or learning of song phrases. A distinctive Blackbird T. merula song may be in use one year. To what extent has the same bird continued it the following year? Or has the original Blackbird given way to a younger bird making an attempt at keeping the motif intact ? If so, then is the young bird one of the offspring or from a neighbouring family? On October mornings the Chaffinch may be heard to indulge in a great deal of 'pinking', and occasionally this will develop into a stuttering, incomplete song. The recording and study of sub-song is still very much in its infancy (see Thorpe and Pilcher 1958). Here again sound libraries have little to offer and it is up to our new breed of recordist to break new ground and contribute much-needed material.

A great deal remains to be learnt from a study of the variation in song with season of the year, time of day, and temperature. Although variation in terms of frequency and length of song period has been worked out for a few species, there remains the question whether the composition of the song itself is influenced. It is this kind of qualitative analysis that presents a fertile field of activity for the recordist. We know that long, high-pitched notes are used by many garden species when an aerial predator is around. This kind of sound is particularly difficult to locate, whilst the harsh 'chack, chack' of a Blackbird mobbing a Tawny Owl Strix aluco is very easily located and all the small birds soon home in and join

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in the fun. But this is only a very broad distinction and many thin 'seep' notes are used in circumstances other than alarm. In the winter of 1974/75 a Great Tit Pants major in my garden at Purley, Surrey, showed what appears to be a clever piece of deception. It would arrive at the bird table only to find it crowded with House Sparrows, Blue Tits Pants caeruleus and Starlings Sturnus vulgaris, and with barely a foothold available; not dismayed, it called the thin 'seep' alarm note and all the birds quickly dived for cover, leaving it in sole charge. This became almost a ritual, the other birds always responding in just the way it wanted. The longer one works a small habitat regularly and thoroughly the more one comes up against embarrassingly fundamental questions which require an answer.

Turning to the opportunities awaiting the travelling recordist, here too the possibilities are many and wide-ranging. Regional variations in song and calls is a subject which still holds many unsolved problems. Twenty-six species of passerines have been proved to demonstrate calls which descend in pitch progressively the farther south they are found in their range (see Ghappuis 1969). Thus, the Blackbird's pre-roosting call is noticeably deeper in Morocco than in northern France, and a cline of progressively deepening calls can be shown for intermediate areas. Ghappuis attributed a survival advantage to this in that deeper calls carry farther in the larger territories which have to be maintained in the less crowded habitats of Spain and North Africa. But do deeper calls carry farther and is there any evidence of pitch variation with change in environment elsewhere? The northern, nominate, race of die Bullfinch Pyrrhula pyrrhula presumably occupies large territories in the vast forest areas of Scandinavia and certainly has a deeper call than his counterpart in the south.

If we take, for example, the Song Thrush, is there sufficient evidence to support the contention sometimes held that repetition in its song is more prevalent where its breeding population is dense ? With so many birds singing in close proximity is repetition of value in avoiding errors in location? There is a recording in BLOWS of a Song Thrush singing in a remote part of Lapland which was apparently the sole representative of its species for many kilometres around. It sings for a quarter of an hour with few repeats. But what is the good of only one example ? Much more recording effort is needed to lend credence to this theory. The Redwing T. iliacus is also interesting because, quite unlike its close relative the Song Thrush, it displays a very remarkable variation in song pattern throughout its breeding range. So the traveller in nortihiern latitudes, particularly if he wanders in an easterly direction through north Sweden into Finland, will find changes so abrupt that visual con-

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firmation of the species is sometimes called for. What happens at the boundary of a particular song area ? Is there an overlap territory where two different songs can be heard? Does one song pattern persist in the same area year after year? Redwing song in Iceland also varies with locality, but is there a general characteristic to be found in all the Icelandic songs which distinguishes that population from Scandinavian stock? If so, how are our Scottish birds singing?

Many field ornithologists undertake expeditions each year to study species that are difficult of access in their breeding habitats. Whedier these journeys be to the deserts of North Africa or to the mountains of Teheran there are species to be found for which no sound record­ing yet exists, or so little as to amount to nothing of scientific value. In the appendix on page 215 are listed those species for which recordings of any kind are required within the next two years for The Birds of the Western Palearctic; recordings on cassette are quite acceptable, if not for making sonograms at least for just listening to. It must be emphasised that, in the absence of any tape recordings at all, reliance has to be placed on voice descriptions found in earlier texts (in the days before the portable tape recorder, memories played some curious tricks). Recording specifically for the sonogram de­mands rather greater care than usual in that a single example of a species should be recorded in isolation, without overlap from other birds nearby. Noise made by wind and water, even by aircraft, can often be painted out on the diagram but other bird noises are too inextricably bound up with the main subject. An obvious ex­ample of this can be seen in the difficulty in recording at a heronry, though it is, however, usually possible to record a few brief spells with only one bird calling.

All recordings for The Birds of the Western Palearctic should be submitted to the British Library of Wildlife Sounds, 29 Exhibition Road, London SW7. Anyone contemplating an expedition where serious recording activity is planned should contact BLOWS beforehand. Help may be forthcoming in various ways, including the supply of data sheets and possibly a quantity of tape.

Another organisation which encourages and co-ordinates new sound recording work in the field is the International Bio-acoustics Council (IBAC) based at the University of Aarhus, Denmark, under the direction of Dr Poul Bondesen. Founded in 1968, its main function is to keep in touch with research workers throughout the world and to maintain an ability to tell anyone who is doing what, in bio-acoustic parlance at least. For anyone starting out on a new line of research there is always the danger, or good fortune depend­ing on how one views the matter, that someone else is following exactly the same line. The quarterly journal Biophon is intended partly as a platform for airing tentative new lines of research and

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partly as a general news medium; and conferences held every other year in different countries are also mainly for informal exchange of ideas and reading of short and sometimes avant-garde papers. The only prerequisite for membership is enthusiasm for the subject, no subscription being required, at least for the time being. Dr Bondesen may be contacted at the Natural History Museum, Universitetsparken, Aarhus 8000 C, Denmark.

Here in Britain the Wildlife Sound Recording Society is helpful in many practical ways, giving advice on technique and equip­ment through its informative journal Wildlife Sound. Regular field meetings are held. It may be contacted through BLOWS (see above).

EQUIPMENT AND RECOMMENDATIONS

I feel at this stage that further exhortations should be withheld until all idea of tape-recording in the field as a burdensome tax of one's physique is dismissed. The opportunist equips himself with a set of comparatively simple and inexpensive tools for the job—a small battery-operated tape recorder, a reasonable microphone and a glassfibre parabolic reflector. The recorder should be the smallest and cheapest available consistent with the following attributes, which are necessary for use in the field. There must be provision for monitoring the recording by plugging in a lightweight stetho-phone or ear-phones. It is an advantage to have a remote control facility for the tape transport independent of the amplifier; this should not be in the form of a switch on the microphone, which proves too noisy in operation, but on a separate lead and switch. It is useful to have a machine with a good volume on playback as there are occasions when, for example, the presence or absence of a species can be readily ascertained by playing its song or call in the field. The controls should be easy to operate by feel alone. Rather obviously, the recorder has to be robust and supplied with a stout case. Finally, the choice should fall on a well-known make for which there are adequate spares and service backing. Perhaps less obviously, there are one or two features which are best omitted. One, which is all too common nowadays, is the automatic volume control. Its action tends to boost any background noise between spells of bird song, and though it is only doing its job the result is thoroughly unpleasant to listen to. There has, therefore, to be pro­vision for manual control whereby the automatic circuit is elimin­ated. This implies that there should also be a means of indicating the level of incoming sound so that the control can be set to avoid overloading the tape. Normally this is catered for by a small meter which serves the dual function of checking both sound level and battery condition. Another sophistication to be avoided is any

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form of so-called noise-limiting device. These work well for music but have proved a disadvantage in field recording.

With light weight and compact size both vital ingredients for the opportunist recorder, one naturally tends to favour the cassette machine rather than the traditional reel-to-reel design. Despite the low tape speed (all cassette recorders run at only 4.76 cm/sec), the quality from a good design properly used is acceptable for most scientific needs. The trouble is that, with the present enthusiasm on the part of most manufacturers for automatic volume control, the choice is somewhat limited. It may be helpful therefore to mention a few examples that have come to my notice and appear to fulfil most of the requirements mentioned above. It should be realised, however, that the current period is one of rapid development in cassette recorders and models are constantly being withdrawn and replaced by new designs.

The ITT Studio 60 M, retailing at £58 including carrying case, weighs 2.4 kg with batteries and may be used with the new Chromium Dioxide tape, which has a better performance at high frequencies. The Sony TC 92 is slightly lighter and more compact but is sold without a case and costs £11 more. Two other models which are known to perform well but which are slightly heavier and larger are the BASF 9202 and the Philips N.2225, retailing at £75 and £81 respectively. There is a stereo model, the ITT Studio 73, weighing 3.2 kg and costing £80 including carrying case. For those who, understandably, wince at the thought of four recording tracks being accommodated within the tiny width of a cassette tape I have a few words in support of stereo later in this review. Finally, for those who can afford the ultimate in quality and yet also the smallest in size there is the Nagra model SN, at £1,026 (fig. 1).

Fig. 1. Three tape recorders, compared in size with a matchbox. Left to right, Nagra SN, Bush TP 60 cassette, and Uher 4200 Report Stereo (drawing by

Annie Michael from photo by P. J. Sellar)

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Weighing under 0.7 kg and easily slipping into a shirt pocket, this is a reel-to-reel design using cassette-sized tape full track and running at 9.5 cm/sec. Curiously, even Nagra are smitten with the craze for automatic volume control and this tiny masterpiece has to be used with an accessory which overcomes this problem. All the prices quoted include 25% value added tax.

Turning to the choice of a microphone, one may be tempted to assume that the one supplied with the recorder should be adequate. Unfortunately this is often not the case as they are usually of the indoor type and very prone to wind noise if used in exposed situa­tions out in the field. A good quality moving-coil or 'dynamic' microphone is the best choice for field work. Another, and generally more costly, design is dependent on the movement of condenser plates but trouble has been experienced with some of these models giving rise to crackle when damp. A third basic design is the ribbon microphone: although capable of high quality results, it is not suitable for outdoors, being abnormally susceptible to wind noise. It matters little whether the directional response is omni- or cardioid. The latter implies a preference for sound coming from the front with less sensitivity to sounds coming from the sides or rear. A microphone of this type does have an advantage when recording at a known song perch. One important point to check, whichever model is chosen, is the electrical impedance. This must match the input to the recorder but should not exceed 600 ohms as, otherwise, there will be a distinct loss of sensitivity when long cables are used.

Grampian Reproducers Ltd, of Feltham, London, market a range of omni-directional dynamic microphones costing between £12 and £15 which have proved themselves in the field. There are a number of rugged designs at around £30 yielding high quality results: of these, the Calrec CM 450, the Sennheiser MD 21 and the Beyer M 69,1 know well and can recommend. The last mentioned has a fairly directional response.

Microphones should be handled with reasonable care and it is particularly important that they are not left out for long in wet weather without at least some protection from direct rain. Finally, moving-coil microphones should never be allowed to come into contact with tape as there is a risk that the strong magnet may cause erasure of recordings.

For the opportunist a parabolic reflector is essential, yielding as it does something in the order of 15 times magnification of sound. So many interesting calls associated with courtship or alarm present themselves in the field with little or no warning and a recording has to be made on the spot. Most reflectors are notv made in glass-fibre as this makes for quietness in handling and light weight.

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Grampian Reproducers Ltd still market their 24-inch (ol6-metre) model in spun aluminium, and this is much improved by the appli­cation of a layer of polythene foam on the back. Membership of the Wildlife Sound Recording Society brings one into contact with a number of enthusiasts who make their own reflectors and can

Fig. 2. The Dan Gibson parabolic reflector with transparent bowl. A compensating amplifier is built into the handle (drawing by Annie Michael from photo by

P. J . Sellar)

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generally be persuaded to make one to order. The cost of reflectors varies from £ 8 to £15. In theory a reflector is incapable of con­centrating any sound of a wavelength exceeding its diameter. The diameter required for the Bittern Botaurus stellaris would be at least 1.5 metres, however, and hopelessly unwieldy. A minimum of 0.5 metres is commended, slightly larger being ideal.

The reflector's inability to respond equally to a wide range of frequencies is a point to be borne in mind with some species, although in practice this does not seem to have a noticeable effect on the shape of a sonogram made from such a recording. The difficulty in observing one's subject will make a more immediate impression on die user in the field. It helps, therefore, to have a peep-hole and fore-sight, both of which are available on the Gram­pian model. A more novel approach to these problems is seen in the Dan Gibson transparent reflector (fig. 2). The handle incor­porates an amplifier specially designed to compensate for lack of bass response, and a microphone is built into the fore-sight. Un­fortunately this model costs £125. The ease witfi which handling noises are transmitted to the microphone is a point to watch. To combat this tendency it often helps a great deal to wrap a generous swathe of chamois leather round the handle.

Use in the field The complete sound recording kit must be sufficiently compact and lightweight so that one is never deterred from taking it into the field even on the most casual outing. Carrying everydiing slung over the shoulder is tiring after quite a short spell so it is a better plan to stow the recorder in a rucksack and have the reflector con-veniendy slung over the top, at the same time keeping off the rain. The microphone should be permanendy fixed in its holder within the cup of the reflector, but it does make for easier carrying if this fixing can be either semi-retractable or folding. Only a quick adjustment should then be needed to reinstate the microphone in its precise recording position, that is at the focal point of the parabola. In this state of semi-readiness the wiring from die micro­phone and the monitoring head-set should be permanently plugged into the recorder. The head-set can be conveniently stowed in a jacket pocket. The whole may be put into action very quickly after removal of the rucksack.

An arrangement conferring the advantage of a greater degree of readiness is to keep the recorder amplifier switched on while still in the rucksack but to have the tape transport remote-controlled by an on/off switch. The reflector should now be shoulder-slung. In order not to run down the recorder battery too quickly, this procedure should be confined to periods of anticipated high activity

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on arrival at a promising area. With the recorder still in the sack there is the problem of setting the gain control, though with ex­perience one soon learns to adopt a setting which will cope with most situations. At least one is able to record at a moment's notice. With something on the tape it may always prove possible to make adjustments at a later stage in the recording sessions.

Use in the garden Foresaking the field for the armchair, let us take a look at what may be done at home—the permanent set-up in the garden. Having regard to electrical input impedance limits mentioned earlier, the recorder may be connected to long microphone cables run out to selected fixed points out of doors, the control position being retained in a room frequendy occupied and having a commanding view of the garden. The microphones are strategically placed in promising situations, such as close to feeding tables, nest boxes, song perches or food specially laid out as a lure. They should be sheltered from direct rain and wind but kept well clear of foliage or grass, which may rusde and spoil a recording. Although not essential, it is an advantage to have a mixer unit accepting, say, four inputs from microphones in the garden and one output connected to the recorder.

In listing the desirable attributes of a simple cassette recorder no mention was made of the choice between mono and stereo. Whilst one cannot pretend that the added realism of a stereo recording greatiy enhances its scientific value there is the advantage of having two input channels available. Thus the second input of a stereo recorder can be put to great effect in simultaneous note-taking. Nowhere is this more useful than in the garden layout, for all the microphones are out in the field and there is therefore no ready means of documentation. A hand microphone and a second channel enable one to describe exacdy what is happening simultaneously with the bird's vocalisation. This procedure adds very considerable value to die recording from a scientific standpoint.

NOTE-TAKING

The reader will have gathered that in this kind of field, accurate and spontaneous documentation is of the very essence. One must at the same time be fully aware of dangerous pitfalls, and these are precisely tiiose which bedevil ordinary field notes, only the temp­tation seems stronger. It is all too easy to draw premature conclusions in interpreting motivation. The very inflexion of a call note may suggest aggression when in fact quite another mood may prevail. It is surprising how reluctant people are to commit their own voice to tape, but it is better to err on the side of saying too much than

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too little. The same goes for recording the bird; too often beginners record in short snatches, missing the really interesting call with behavioural significance. The shortcomings in the scientific approach of many recordists should prove much less of a hurdle to the prac­tised field ornithologist, and this is just why it is important that he takes up this activity. It will benefit his own field work as well as provide much needed fresh material for bio-acoustic research.

THE VALUE OF RECORDINGS

That last sounds a somewhat glib statement but, in fact, one of the pleasures to be enjoyed in what we should now call scientific sound recording is the satisfaction of knowing that, even if only an occa­sional participant, one can contribute usefully. A complete beginner can make an isolated recording which, if properly documented, filed and indexed, may at some future time turn out to have quite unsuspected significance. For example, I placed my microphone late one night in 1968 at the entrance to die burrow of a Leach's Petrel Oceanodroma leucorhoa and let the recorder run for about ten minutes before moving on. Many months elapsed before I realised that here was the first recorded evidence that male and female churr together at the nest. Many more months passed before I found that here, too, was an example of antiphonal song, in which one partner's churr would always be interrupted each time the other broke into the 'flight' call. Yet more information was wrung from the recording quite recently when die speed of the first bird's reaction to die other's 'flight' call was found to be 50 milliseconds, which is indicative of the species' aural response time. This ability to discern exceedingly short time intervals is die only respect in which a bird's hearing equipment differs considerably from our own. All this, it must be emphasised, could equally well have been elucidated had the recording been quite mediocre and made on a simple cassette machine.

SOUND LIBRARIES

The chances of any such recording contributing to bio-acoustic research are greatly enhanced if a documented copy is lodged with a sound library. The value to future research of, say, five thousand recordings in a well-organised sound library is far greater than it would be if the same number was languishing in individual collections. They can be filed in an orderly fashion and listed in regularly up-dated catalogues. Such a pooling of material makes any study of geographical, individual or temporal variation in song a much more viable project. Hitherto the lone researcher has had to rely on recordings cajoled from recordist friends; now he has access to a wide range of material all carefully stored oft species

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reels, every recording documented to at least a minimum standard. The natural history sound library movement has been slow to start but is now gathering pace. For a long time the only one of any size was the Library of Natural Sounds at the Laboratory of Ornithology, Cornell, Ithaca, New York. This was founded by Dr A. A. Allen and Dr P. P. Kellogg in the 1930's. The first in Britain was the BBC Sound Archive, which by 1973 contained 3,199 separate recordings or 'cuts' of 729 species of birds. BLOWS was opened in 1969 as part of the British Institute of Recorded Sound. It houses not only a complete copy of the BBC Sound Archive but a large collection of commercial discs of wildlife sound. The BBC naturally tends to foster recordings which will lend atmosphere to a television or radio programme, whereas the material on tape from individual recordists can be more easily suited to the requirements of scientific study. In this respect the library plays an active role in encouraging recordists to fill gaps in the collection of complete vocabularies of certain species. It has recently lent support to a number of expe­ditions in return for copies of recordings fully documented in line with a standard procedure. ,

Depositing recordings What is involved in preparing a recording for submission to a library ? If, as is quite likely, our newly converted field ornithologist has but one humble cassette recorder, how does he set about making copies and editing all the wind and aircraft noise out of his tape ? In this case the library will be found quite willing to accept original cassettes and do all the editing and copying on the premises. It would, as a second step in one's progress, be a great advantage to acquire, for example, a second-hand mains recorder of the reel-to-reel type to which one could transfer recordings directly from the field machine. Editing on the open reels is then a simple matter. Such a machine can also serve duty as the in-house recorder for the garden set-up. Perhaps most rewarding is the ability to replay one's recordings with the quality they deserve. Oldish but thoroughly reliable Ferrographs or Vortexions generally prove an excellent buy for around £50.

The BLOWS library has now standardised a system of docu­mentation using a specially designed data sheet to be completed for each separate recording. The least that is asked for is the name of the species, the locality and date of the recording and the re­cordist's name and address. The recording itself should be intro­duced by a dictated announcement on the tape, again giving the name of the species, the name of the recordist and the serial number of the data sheet. Thus, every recording is positively linked to its data sheet and no confusion can ever arise. The recording has now

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become a scientific specimen in the same manner as a bird skin with its label in a museum; it is there for posterity.

COPYRIGHTS AND REWARDS FOR THE RECORDIST

I t is all very well extolling the virtues of depositing copy recordings and amassing a wealth of material under one roof for the benefit of research, but what is in it for the individual recordist? He is the one who seems to have to do all the hard work and gets nothing in return. Does he even place himself a t some disadvantage? Sound libraries generally operate a scheme to protect the contri­butor against commercial or unauthorised use of his recordings. At the same time any copyright remains with the recordist who is left free to put his material to any future commercial use if he wishes. Copies of recordings are issued only to bona-fide research workers, who are obliged to acknowledge the recordist in any published work featuring his material, whether this is simply re­ferred to in the text or directiy represented by a sonogram. If a commercial request for a recording arises, the library will put the enquirer in direct touch with appropriate recordists who may then negotiate terms. In many ways, then, the library acts as a focal point between recordists in the field and various kinds of user. I t is a two-way operation for there are cases when the library will commission recordings of a particular species or promote a com­plete programme of work in the field. T h e individual recordist thus has a ready means of making a direct contribution and therein lies the satisfaction. There is the consideration, too, that the library provides a safe repository for copies of all his best recordings. Ideally the library, or a t least the present network of a dozen or so national wildlife sound libraries throughout the world (see Boswall 1974), should aim to collect every sound of biological significance, including geographical, temporal and individual variations, of all species of wildlife. Tha t ideal will, of course, never be fully realised, but I hope I have shown that the appetite for material, far from being satisfied with all tha t has been achieved already, is greater than ever before. In fact the whole business of systematic collection of natural history sounds is only just beginning.

SUMMARY

Birdwatchers are encouraged to take up sound recording now that the equipment is so much reduced in size and weight. The need for new recorded material is stressed and several fertile fields are suggested. Guidance is given on the selection of equipment, and the methods of documenting and processing recordings so that they can more readily contribute to research are outlined.

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REFERENCES BOSWALL, J . 1974. 'A preliminary world list of wildlife sound libraries'. Recorded

Sound, 54: 276-277. CHAPPUIS, C. 1969. 'Un cline vocal chez les oiseaux palearctiques: variation tonale

des vocalisations, sous differentes latitudes'. Alauda, 37: 59-71. MARLER, P. 1956. 'The voice of the Chaffinch and its function as language'.

Ibis, 98: 231-261. SIMMS, E., and WADE, G. F. 1953. 'Recent advances in the recording of bird

songs'. Brit. Birds, 46: 200-210. SUMMERS-SMITH, D. 1955. 'Display of die House Sparrow Passer domesticus'. Ibis,

99: 296-305. THORPE, W. H. 1958. 'The learning of song patterns by birds, with special reference

to the song of the Chaffinch Fringilla coelebs'. Ibis, 100: 535-570. , and PILCHER, P. M. 1958. 'The nature and characteristics of sub-song'.

Brit. Birds, 51 : 509-514.

Appendix. List of species for which sound recordings are urgently required for the second and third volumes of T h e Birds of the Western Palearctic' Lappet-faced Vulture Torgos tracheliotus Greater Sand Plover C. leschenaultii Sooty Falcon Falco concolor Caspian Plover C. asiaticus Caucasian Blackcock Lyrurus Pintail Snipe Gallinago stenura

mlokosiewiczi Senegal Thick-knee Burhinus senegalensis Caucasian Snowcock Tetrogallus Egyptian Plover Pluvianus aegyptius

Caucasian White-eyed Gull LOTUS leucophthalmus Caspian Snowcock T. caspius Great Black-headed Gull L. ichthyaetus Sand Partridge Ammoperdix heyi Grey-headed Gull L. cirrhocephalus Double-spurred Francolin Francolinus Sabine's Gull L. sabini

bicalcaratus Ross's Gull Rhodostethia rosea Arabian Bustard Ardeotis arabs Lesser Crested Tern Sterna bengalensis Houbara Bustard Chlamydotis undulata White-cheeked Tern S. repressa Andalusian Hemipode Turnix sylvatica Bridled Tern S. anaethetus Kitditz's Plover Charadrius pecuarius

P. J. Sellar, 8g Riddlesdown Road, Purley, Surrey CR2 IDH