Grallina Cyanoleuca in This Paper I Describe an Unusual Foraging
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AUSTRALIAN 238 HOBBS: Australian Magpie-lark, Feeding Method BIRD WATCHER Gyrating as a Feeding Method of the Australian Magpie-lark Grallina cyanoleuca In this paper I describe an unusual foraging behaviour observed among Australian Magpie-larks Grallina cyanoleuca at Dareton, New South Wales (July to mid August 1984) and Buronga, N.S.W. (July 1985). At Dareton at least six Magpie-larks were seen feeding in a freshly mulched strawberry patch in which many small earthworms Lumbricus sp. were present several centimetres below the surface. In an open area between the plants each Magpie-lark gyrated on a single spot, shuffling its legs quickly as it moved in a small circle. No distinctive foot movements such as kicking or stirring were noted. This action formed a saucer-like depression in the mulch about 15 em in diameter and up to 3 em deep, sufficiently deep to expose the worm layer. After five or six turns the Magpie-la:rks stopped, made a half turn in the reverse direction, and picked up any exposed worms. It is possible that some worms wriggled upwards into the depression in response to the disturbance caused by the moving feet. The gyrations were made in both clockwise and anti-clockwise directions. This behaviour continued daily until mid August by which time foliage of the strawberry plants was covering the mulch, making it inaccessible to the birds. At Buronga, I watched five Magpie-larks feeding in an irrigated pasture. Water had receded leaving a small pool about 2 em deep in a grassed depression. The Magpie-larks were walking and standing in this pool and gyrating in the same manner as observed at Dareton. On this occasion their turnings were not limited to six but were more continuous, over twenty revolutions being frequently seen. During the gyrations the Magpie-larks were constantly picking objects from the surface, presumably animal organisms disturbed from the bottom of the pool. They did not stop to feed but flicked their heads from side to side to grab the food with the bill as they were turning. They were watched for some fifteen minutes before they took alarm and flew off. Examination of the pool revealed the presence of many dead or near-dead earthworms and an assortment of small insects, including beetles. There are numerous references in the literature to foot and leg movements by birds as an aid to feeding and such use is accepted as regular in many non passerine groups. Herons (Ardeidae) 'foot-stir' or 'foot-rake' in water or water weed; gulls (Laridae) and ducks (Anatidae) 'foot-paddle' in water or on grassland; plovers (Charadriidae) 'foot-tremble' on mud, and of course phalaropes (Phalaropodidae) 'spin' on water and infrequently on mud (e.g. Hancock & Kushlan 1984; Simmons 1961a,b). Such movements are almost unknown in passerines although 'foot-trembling' on grass has been recorded for the Hermit Thrush Hylocichla guttata (Brackbill 1960) and for the Flame Robin Petroica phoenicea (Hobbs 1954). This gyrating method of feeding by the Magpie-lark does not closely resemble that described for any other species but it has the same purpose or effect, that is of exposing or bringing to the surface hidden animal organisms. It appears to be a successful and rewarding method although a possible disadvantage was suggested when a Magpie-lark was seen in my garden for several days with both its legs bound together with red twine. The unfortunate VOL. 11 (7) SEPTEMBER 1986 GEARING: Black-breasted Buzzard, Aerial Display 239 bird progressed in a series of hops, but appeared to be getting food. It was constantly pecking at the confining twine and may have released itself eventually. References Brackbill, H. (1960), 'Foot-quivering by foraging Hermit Thrushes', Auk 77, 477-478. Hancock, 1. & Kushlan, 1. (1984), The Herons Handbook, Croom Helm, Beckenham. Hobbs, J.N. (1954), 'Flame Robin's foot-pattering feeding habit', Emu 54, 278-279. Simmons, KE.L. (1961a), 'Foot-movements in plovers and other birds', Brit Birds 54, 34-39. -- (1961b), 'Further observations on foot-movements in plovers and other birds', Brit. Birds 54, 418-422. By J.N. HOBBS, 12 Hume Street, Dareton, New South Wales 2717 • Aerial Display of the Black-breasted Buzzard Hamirostra melanosternon On 30 June 1983, in company with my wife, I observed a pair of Black breasted Buzzards Hamirostra melanostemon at Evans Head on the far north coast of New South Wales. The locality itself is quite noteworthy, although a few sightings of this species have been made in the general region in preceding years (Blakers et al. 1984) and our sighting followed a period of severe inland drought. The birds observed by us were in flight at 1130 h on a warm, clear day. The male was a dark phase bird: black on the head and breast with a distinct rufous nape that appeared slightly crested; otherwise dark with some reddish brown on the under-wing coverts and white 'bullseyes' in the broad wings, and a short, full, ashy-brown tail; eye dark with a pale eye-ring (orbital skin); tarsi bare. The larger female was a light phase bird, brown with black streaks on the breast. In gliding flight the birds' wings were held more upswept than in the Wedge-tailed Eagle Aquila audax. We have observed Black-breasted Buzzards elsewhere (in the Northern Territory), and are sure of the identity of the birds at Evans Head. We visited the locality two years later, but found no Buzzards; the area has changed with much more vegetation about the sand dunes. The male Buzzard was flying at about 45 m and suddenly dived steeply, with his wings fully open and talons down, to within 15 m of the ground. He seemed to halt momentarily with his feet lowered and then climbed vertically to his original height, flipped over and dived again. The female was flying below, at about 15m, and appeared to take no notice; the male again climbed to his original height. He made a third dive and then followed the female in a slow and controlled flight into a lightly timbered area behind the coastal cliffs and sand dunes, where they landed in the trees. While undulating, the male's plunge of c. 30 m took a few seconds and the very powerful climb not much more. The bird gavt:: the impression of great manoeuvrability and powerful lift. Cupper & Cupper (1981) recorded similar behaviour by a high-soaring pair, in which one (presumably the male) repeatedly dived at the other which rolled and presented its talons, perhaps touching its mate's talons on one pass. Hollands (1984) observed a pair to lock talons in such a display, and 'cartwheel' downwards. .