June 1969 ] COOPER, Swamp Harrier 153

broken only by an occasion click, click and expectant twitterings and cheepings when a group of adult birds returned to the cave. Some birds entered the cave without making any sound, circling round as if waiting for their noticeably large eyes to adjust to the darkness, after the bright sunlight outside. If the torch was shone the click, clicking started again immediately. Is this an alarm call or an "audible echo location"? Possibly it serves both purposes.

The nests, which covered practically every available space on the rock-face, appeared to be constructed mainly of moss or pine fronds, held together by a sieve-like structure of the substance which, I understand, is regurgitated by the birds to fix the nests to the rock-face. In some cases the moss was so sparse that the egg could be seen clearly through the bottom of the nest.

A cliff rose sheerly for 100 feet or more from the deep rock-pool adjacent to the cave. Birds leaving the cave flew, with rapid wing­beats, out over the rock-pool until nearing the cliff-face, when they appeared to be caught in up currents of air and swept aloft. They entered the cave at the top of the entrance slit and swooped out from the lower end.

I wonder if these Grey Swiftlet nesting colonies in the Tully Gorge have been visited before, and how the number of nests counted last November compare with previous counts. Possibly some of the birds from the depleted colonies on Dunk Island have moved across to the seclusion of the Tully Gorge.

The Mating Flight of the Swamp Harrier By ROY P. COOPER,* Melbourne

On September 3, 1966, a pair of Swamp Harriers (Circus approximans) appeared to be nesting in a reed-choked swamp, on the western side of the road, a mile north of Darby River, on Wilson's Promontory, in southern Victoria.

From a near-by eminence I was able to see that an area in the rushes, about eight to ten feet across, was below the level of the surrounding vegetation, and it appeared that the bent over reeds would form the base of a nest.

On three separate accasions during the day I flushed a bird from this hollow area. Each time it was the smaller, brighter coloured bird.

The description that was taken of the plumage colouring of both birds showed that there was a great difference between the sexes.

The smaller bird, which was presumed to be the male on account of its small size, and later by its actions in the mating flight, had the back and wings brownish-chestnut, with a distinct greyish wash across the primary coverts; the anterior half of the flight feathers was black, with the remaining portion and all the second­aries mid grey; there was a large white patch on the rump; the under surface was chestnut with black tips . to the primaries and

*Wilson's Promontory Bird Survey Group

154 COOPER, Swamp Harrier [ Bird Watcher

light grey on the remaining part of these feathers and on all the secondaries.

The chestnut colouring on the under wing and body, with the grey on the secondaries and the posterior part of the primaries, with the black tips, were indicative of the Spotted Harrier (C. assimilis). However, the absence of spots on the plumage; the type of call and the habitat leaves no doubt that this bird was a Swamp Harrier.

The larger bird, which by its large size and its subsequent actions, was presumed to be a female, was dark brown on the upper parts with a small white patch on the rump, and reddish-brown on the under surface. The plumage pattern indicates that it could be a young bird in its first breeding season.

There have been Swamp Harriers on this swamp for the past five to six years, but at no stage has their plumage colouration been unusual enough to note specifically.

When they were disturbed by me the male (the smaller) bird would flush from the nesting site, while the female (the larger bird) would fly up from the dryer areas on the edge of the swamp, or from a perch on a dead tree, or the margain of the timber at the back of the lake.

The female, being on a vantage point, was the first bird to fly up in alarm, and its loud cries would cause the male bird to join it immediately from the nesting platform among the rushes.

Both birds then flew around the edge of the swamp, at an alti­tude of one to two hundred feet, in an upward and then a downward spiralling or circular pattern, the male bird being a few feet and sometimes a few inches above the female.

The wings were at an elevation of approximately 45° above the body and the wing beats were short.

The male bird carried his feet in a relaxed, downward manner and he would sometimes touch the female on her back. The female, the lower bird, while in this position would keep her legs and feet tucked up out of sight under her body.

On three occasions the smaller bird (male) hit the larger bird (female) firmly on its back with its feet . Immediately the lower, larger bird dropped its talons and, with a quick flip of its wings, it rolled onto its back and grasped the male by one foot.

With one set of talons of each bird locked together the two birds swung around in a downward spiralling circle. The action was similar to two young girls grasping a hand each and swinging around in a circle as fast as possible, usually with one or both girls falling to the ground .

The bodies of the two birds were at an upright angle of about 45° to each other, and the wings were still held in the vertical V shape. Occasionally there was an upward movement in the flight pattern, and then they would break apart and continue to fly around the swamp, with the male bird a few inches above the female.

June 1969 ] HINDWOOD, Making of a Book 155

On two different occasions when the female turned over on her back, she remained in that position, and the bodies of both birds were momentarily touching. After the second contact the birds broke apart and flew off in different directions and the display was finished. It would appear that the birds had mated, but it was not possible to observe it fully, as the contact between the two birds was so short, and they were approximately one hundred yards away from where I was watching through 8x field-glasses .

When either bird was disturbed by my presence, and it flew up from the swamp or from a tree, it usually uttered a single, high­pitched note, repeating it every second or two until up to ten or twenty calls had been given.

It would then be joined by its mate and both birds would fly in the vertical pair formation, without uttering any sound.

Sometimes, when they broke apart for a distance of 50 to 60 feet, the call would be given again, and immediately they would come together and continue their paired flight, without uttering any calls.

This behaviour was observed for over an hour on three separate occasions during the day.

The Making of a Book-Some Useful Australian Birds

By K. A. HINDWOOD, Lindfield, New South Wales

In 1921, there was published, by the Department of Agriculture of New South Wales, an attractive and informative book of 62 colour-plates, and related text, titled Some Useful Australian Birds. The author was Walter W. Froggatt (1858-1937), Government Entomologist and a notable naturalist with wide interests. He wrote with authority on many subjects and was, at the time, President of the Royal Zoological Society of New South Wales.

It is interesting to trace the background to this book and its genesis. Between 1896 and 1905 A. J. North, Ornithologist to the Australian Museum, published in the Agricultural Gazette of New South Wales a series of illustrated articles under the heading "A List of the Insectivorous Birds of New South Wales". Six parts, in which 161 species were discussed, appeared; three of these parts were later issued as separates.

The interest aroused by North's papers was such that it was decided a few years later to produce, also in the Agricultural Gazette, a second series under the title "Insectivorous Birds". The Editor of the Gazette, J. E. O'Grady, assisted by A. I . North, prepared the matter issued during the years 1910-1913; then Walter Froggatt took over and completed the run in 1914 and 1915. The 60 colour-plates in the set (36 with O'Grady's text and 24 with Froggatt's) are based on those in Gould's Birds of Australia, but