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Ornithologists in north Queensland: Part III

1918; Taylor & Francis; Volume: 17; Issue: 4 Linguagem: Inglês

10.1071/mu917180

1448-5540

W. MacGillivray,

Animal Ecology and Behavior Studies

Sula ecyanops (Parasula dactylatva personata).-\have little to add to my description of this species which appeared in The Emu of December, 1910, as a result of the visit paid to Raine Island by Dr. Dobbyn and myself a month previously.We then found numbers of fresh eggs, hatching eggs, and young in various stages of development.When Mr. M'Lennan visited Raine Islet in July, 1911, he found this species commencing to nest.When we spent a week there in December, 1913, nesting had just about finished ; only one nest contained eggs.We also found this species nesting on the large sandbank on the Barrier Reef, about 12 miles north-west from Raine Islet.During our stay on Raine Islet our attention was frequently arrested by a rushing sound, which we found to be due to a peculiar habit of this species.When returning from a distance they do so high up until over the edge of the island, when they suddenly swoop down with half-closed wings to the nest or young, after the manner of a Falcon stooping to its quarry, and at an equal, if not greater, rate of speed.This is possibly done to evade the attentions of the Frigate-Birds, who are always hovering aloft on the watch to relieve incoming Gannets of their cropful of fish.The fully-fledged young bird has the head, neck, and breast white, mottled with brown, and the wings brown.Sula piseatrix (Sula piscatoy vubyipes).-Thenesting season of the Red-legged Gannet on Raine Islet seems to extend from June until December.When the islet was visited by Mr. M'Lennan, in July, 1911, he found that nesting operations had not long commenced, only a few nests containing either the single egg or a newly-hatched young bird.It was just about over when | Dr. Dobbyn and I examined the islet on 30th October, 1910, and only a few stragglers were nesting when we visited it in December, 1913.A few nests contained an egg ; more contained young at varying stages of growth, but there was a great number of young birds that had left the nest either still being cared for by their parents or fending for themselves.These, together with adult birds, roosted all together in larger or smaller communities-a habit not resorted to by either of the other species.The nest, a substantial interwoven platform of sticks, 8 to 12 inches in diameter, depressed to about 1 inch in the centre for the single egg, is, unlike that of the Brown or Masked Gannets, always built a foot or more off the ground, on a low, shrubby growth common on the islet, or on some small trampled-down bush.The egg is smaller and more of a long oval than that of the other species.It is white, with a limy coating, which is soft when the egg is first laid, and then easily receives impressions from the nest or Dirds' claws, but soon hardens on exposure.It is easily removed when wetted, exposing a pale greenish shell.An average egg measures-axis, 60 mm.; diameter!49 mm.The nestling is hatched out blind, with a le leaden-coloured skin, only an indication of down on the head, back, humeral and femoral tracts, and on each side of the breast.The bill is shorter and the e ee Vol.XV 1918 | MACGILLIvVRAY, Ornithologists in North Queensland t81 mask much darker than in the nestling of either the Masked or Brown Gannets.The eyes soon open, and the bird becomes thickly covered with white down, which is worn until the bird is almost fully grown.Then the feathers begin to appear, the primaries and rectrices being the first, then those of the head and back.These birds go through several stages before reaching maturity.No. 1 stage.-Whenfirst feathered, the bill, mask, and feet are black, and the rest of the body dark smoky-brown.No. 2 stage.-Alighter brown all over the feathering, with a dark brown bill and lighter brown feet.No. 3 stage.-Lightbrown all over, with a white tail, horn-coloured bill with a pink tinge round the base, legs and feet and bordering of gular pouch reddish.This stage was found breeding and mated with mature birds.No. 4 stage (maturity).-Purewhite, with dark primaries, light horn bill bordered with pink, and gular pouch bordered with bright pink ; red legs and feet.Birds in all these stages of plumage may be seen roosting together in the groups before mentioned.When asleep the beak is tucked in under the scapulars.The duties of incubation are shared by the parent birds, one sitting during the night, the other by day.Sula fusea (Hemisula leucogastey plotits)-I can add little to the description of the nesting habits of this bird which appeared in The Emu of December, 1910.Mr. M'Lennan found this species starting to nest when he visited Raine Islet early in July, 1911; only a tew nests then contained eggs, and there were no young.When Dr. Dobbyn and I visited it on 30th October, 1910, eggs and young in all stages of growth were in thousands all over the place.When I again visited the islet, early in December, 1913, nesting was finishing, as there were very few fresh eggs or nests, though incubating eggs were plentiful and young birds were everywhere.This species was also nesting on the Ashmore sand-banks and on a large turtle-infested sand-bank on the Barrier Reef, about 12 miles north-west from Raine Islet.The young when feeding puts its beak down the parent's throat.They seem able to accommodate fairly large fish ; one large downy young one disgorged a flying-fish 10 inches long by 14 inches in diameter.The small, naked young feel the heat very much, and the mother bird shelters them by standing over them during the heat of the day.The white downy covering of the larger young sufficiently protects them from the rays of the sun.Fregata ariel (Fregata ariel ariel)-When Mr. M'Lennan_ visited Raine Islet in July, 1911, he found eight nesting-colonies of these birds of from three to thirty nests each, there being 150 nests in all; several of them contained one egg each-two of these were hatching.The rest of the nests contained one young bird each, in all stages of plumage, from birds a couple of days old to those ready to fly.At Bramble Cay, ten days later, he noted a pair of birds, but none was nesting.At Raine Islet in December, 1913, nesting had finished, but numbers of fully-fledged young birds roosted all over the islet, and, 13Emu 182 MACGILLIVRAY, Ornithologists in North Queensland.|. April though able to fly quite well, were being fed by the parent birds.Many were soaring overhead with adult birds, and these latter were very numerous, and constantly on the watch to deprive incoming Gannets of their fish.All three species of Gannets are made to disgorge, and we frequently witnessed encounters between a Frigate-Bird and a home-coming Gannet.The Gannet often manages to elude its adversary by flying low to the ground, but even then they are sometimes forced to drop the fish on the ground, when the Frigate-Bird will alight, pick it up and swallow it, and rise again into the air.They find no difficulty in rising from the ground.They sometimes soar at a great height, and I have counted as many as _ 40 at different elevations directly over our tent, and there were many more aH round the islet.Mr. Kershaw and I kept our eyes on one that passed overhead, sailing with outstretched wings, without any perceptible movement.He sailed down to the other end of the islet, gradually rising higher, then went round several times, and once half-closed his wings to descend about 50 feet ; then spread them out and resumed his sailing flight, never at any time flapping his wings.The only time that they do so is when they are buffeting a Gannet to make it disgorge, or on rising from the ground.When flying the tail is mostly closed like a large pair of scissors with incurving blades meeting at the base and tips.The legs are carried on either side.To show that, powerful fliers as they are, they are not equal to a war with the elements, I will quote the following note from Mr. H.G. Vidgen, made on 31st December, 1913, at Paira, Cape York :-" The wind was of hurricane force ; it blew down trees in numbers and covered the ground with a débris of limbs and twigs.For two days it was so bad that the Frigate-Birds were knocked out.They used to rest on the mangroves in a sheltered spot in our bay by spreading out their wings and lying across twigs and leaves.The birds were present in hundreds-a thing I have not seen before."The fully-plumaged young on Raine Islet were dark brown, with a dirty whitish patch on the chest, the head of the male being fawncoloured, and of the female rufous.In both the iris is brown, bill and gular pouch bluish-white, feet fleshy-white.Female.-Total length 790 mm., wing 570 mm., culmen 110 mm.Male.-Length 790 mm., wing 565 mm., culmen 100 mm.Three eggs collected by Mr. M'Lennan in 1911 measure as follows in mm.:-(1) Axis 65 x diameter 44. 2 gg 1 SOB IR » 43.(3) isp, 207) " 46.Phaethon rubricauda (Sceophaethon rvubricauda novehollandie).-WhenDr. Dobbyn and I visited Raine Islet, in October, rg10, we overlooked this species, the few hours that we spent on the place not permitting of an examination of the caves and crevices.These caves are under the margin of the coralline rock which caps the islet ; some are of respectable dimensions, but the entrances are small, and one has to crawl or wriggle in on one's stomach in order to examine them.The Tropic-Birds are, however, more often tound in small crevices not more than a foot or two in under the rock ledge facing the sea, or in one of the pits or trenches that have been excavated in the centre of the islet.