AUSTRALIAN 20 OLSEN, ROSS & OLSEN: Vestigial Wing Claws WATCHER

Short Notes-

Vestigial Wing Claws in Australian of Prey

During a study of growth and development of the Brown Falcon Falco berigora one of us (TR) noticed wing claws on the tips of the nestlings' alulae (digit II). Six nestlings in two broods all possessed tiny, pink claws that increased in length as a nestling grew. Inspection of a captive Brown Falcon and a series of museum skins confirmed its presence in free-flying birds as a black curved claw. The Brown Falcon is an unusual representative of the Falco and probably the world's most variable falcon in body and size and colour. The addition of a further character to the list of its peculiarities did not surprise us. However, a cursory look at skins of the other five Australian falcons (Peregrine F peregrinus, Black F subniger, Grey F hypoleucos, Australian Hobby F longipennis and Australian Kestrel F cenchroides) revealed strong, curved black claws on all specimens. The claws of three of the nestling Brown Falcons increased in length (chord) from 1.9, 2.6 and 2.1 mm at 8, 9 and 10 days of age respectively, to 2.9, 3.6 and 4.0 mm at 26, Tl and 28 days. At the time of the last measurement they were pink-grey and had not yet turned black, unlike the claws on their feet. The claws of six free-flying Brown Falcons ranged from 3.8 to 7.2 mm (mean 5.4) in length. They were relatively sturdy, emerging from the dorsal surface of the tips of the alulae and curving more­ or-less parallel to the adjacent feathers. They appeared to articulate somewhat with the digit. The claws of the other falcons were similar in colour and form and in length relative to body size. Skins of the Osprey Pandion haliaetus and several other representatives of the Family also had alular claws. Unlike the almost typical claw-like colour of the falcon wing claws they were pale and more fragile. Those of both Letter-winged Elanus scriptus and Black-shouldered Kite E. notatus, for example, snapped off easily when handled. Some individuals of Little Eagle Hieraaetus morphnoides, Wedge-tailed Eagle Aquila audax, Black-breasted Buzzard Hamirostra melanosternon, Square-tailed Kite Lophoictinia isura and Black Kite migrans had pale claws. The Spotted Harrier Circus assimilis and Marsh Harrier C. approximans, Pacific Baza subcristata, Whistling Kite sphenurus, White-bellied Sea-Eagle Haliaeetus leucogaster and the three Australian Accipiter species had hard, horny, grey 'knobs' (the 'spurs' of Fisher 1940) which were fused to the metacarpals, rather than a true claw-like structure. A random check of other species uncovered curved 'knobs' in some owls of the genera Ninox and Tyto, and claws in the Pacific Black Duck Anas superciliosa, Masked Lapwing Vanellus miles (in addition to the spur) and doves Geopelia sp. No claws were found in the Pink Cockatoo Cacatua leadbeateri or Long-billed Corella C. tenuirostris. Fisher (1940) found alular claws in 14 of the 21 Orders of birds he examined. His North American Accipiter and Haliaeetus also did not have claws while Pandion, Elanus and Falco did. He found that claws were more likely to be present on embryos or nestlings, and also found claws on an embryonic, but not on older, Circus. Nero & Loch (1984) reported claws on both digit II and ill in some individuals of the Great Gray Owl Strix nebulosa. The wing claws of birds appear to be vestigial with the exception of those of the Hoatzin Opisthocomus cristatus (Pycraft 1903) and African Finfoot Podica senegalensis (Percy 1963) which are used for climbing. VOL. 12 (1) MARCH 1987 OLSEN, ROSS & OLSEN: Vestigial Wing Claws 21

Illustration showing wing claw on tip of nestling Brown Falcon's alula Plate 6 Drawing by Penny Olsen

Nero & Loch (1984) noted that while such claws may be a 'trivial feature', perhaps persisting since birds evolved from simply because they confer no particular selective disadvantage to the bird, their presence raises some fundamental evolutionary questions. Fisher (1940) considered wing claws to have little significance because of their 'variable, degenerate state'. They seem to be a generally overlooked character that may have some relevance to . For example, the presence of claws (or knobs) of similar colour and form within genera represented by more than one species in , and their presence in North American representatives of the same genera, indicates some taxonomic consistency. That the Black-breasted Buzzard and Square­ tailed Kite both have wing claws adds weight to the view of Brown & Amadon (1968) that they are allied to Milvus, which also possess wing claws. Those kites and kite­ like eagles in which the claws seem to be absent, Haliastur and Haliaeetus, are thought to be related to each other (Ridgway 1873; Brown & Amadon 1968). Further, the presence of a wing claw in Milvus is another character distinguishing the genus from Haliastur (see also Amadon 1978). References Amadon, D. (1978) , 'Remarks on the taxonomy of some Australasian raptors', Emu 78, 115-118. Brown, L. & Amadon, D. (1968), Eagles, and Falcons ofth e UVrld, McGraw-Hill, New York. Fisher, H.I. (1940), 'The occurrence of vestigial wing claws on the wings of birds', Amer. Midi. Nat. 23, 234-243. Nero, R.W. & Loch, S.L. (1984), 'Vestigial wing claws in Great Gray Owls, Strix nebulosi:l', Can. Field-Nat. 98, 45-46. Percy, W. (1963), 'Further notes on the African Finfoot, Podica senegalensis (Viellot)', Brit. Ornithol. Club Bull. 83, 127-132. Pycraft, W.P. (1903), 'The claws on the wings of birds', Knowledge 26, 221-224 . Ridgway, R. (1873), 'Catalogue of the ornithological collection in the museum of the Society. II Falconidae', Proc. Boston Soc. Nat. Hist. 16, 1-66.

By PENNY D. OLSEN1, WNY ROSS 2 and JERRY OLSEN3 1 CSIRO Division of Wildlife & Rangelands Research, P.O. Box 84, Lyneham, A.C. T. 2602 2 42 Willis St, Evatt, A.C.T. 2617 3 RMB 1705 Read Road, Sutton, N.S.W. 2620 •