Pitta 139 November 2002
Redefining an Eagle—Suhel Quader
In this column Suhel Quader
Parry, S.J., Clark, W.S., and Prakash, V. 2002. On the taxonomic status of the Indian Spotted Eagle Aquila hastata. Ibis. 144: 665-675.
uch ink is spilled and many tears shed by taxonomists arguing whether to split subspecies into full species or lump different species into subspecies of a single species. Why should the rest of us particularly care one way or another? MC onservation provides one reason. When attempting to conserve biological diversity, we must often set priorities. One way to do so is to consider evolutionary distinctness. Particularly unique and distinct organisms are given highest priority. For example, according to this hierarchy, each of the many individual subspecies of the Eurasian Starling (Sturnus vulgaris) would be given less conservation importance than the Brahminy Myna (Sturnus pagodarum), which is not divided into separate subspecies. Recently, there has been some rearrangement of the taxonomy of the Indian Aquila eagles, with the separation of the Tawny and Steppe Eagles (Aquila rapax and nipalensis respectively) into distinct species. S.J. Parry, from The Natural History Museum, U.K., and colleagues now suggest a similar split in the Lesser Spotted Eagle (Aquila pomarina), which has two subspecies – the migratory A. p. pomarina of western Eurasia and Africa, and the resident A. p. hastata of the Indian subcontinent. Although pomarina and hastata were originally described as separate species in the 1830s, Ernst Hartert classified hastata as a subspecies of A. pomarina in the first quarter of the 20th century, and this convention was followed by James Peters in his influential Checklist of the Birds of the World. Parry and co-authors revisit this issue by presenting observations and measurements on hundreds of specimens of pomarina, and hastata, as well as the closely related Greater Spotted Eagle (Aquila clanga). They show that pomarina and hastata differ considerably in plumage. A. p. pomarina has a pale head contrasting with darker back, a yellow or amber iris, and a rufous patch on the neck. A. p. hastata, on the other hand, has head and back uniformly dark brown, a brown iris, and no patch on the neck. There are also clear differences between these taxa in measurements of the skull and beak. But these differences in themselves are not evidence that pomarina and hastata should be different species – after all, subspecies within a species differ in some respect too. The clearest evidence that pomarina and hastata should be different species comes from a comparison with A. clanga. The most striking difference is in the width of the gape, which is greatest in hastata, intermediate in clanga, and smallest in pomarina. Because hastata and pomarina are less similar to one another than each is to A. clanga (a different species), all three should be considered separate species. The Lesser Spotted Eagle (Aquila pomarina) is then distinct from Aquila hastata, for which the authors suggest the English name ‘Indian Spotted Eagle’. Why does A. hastata have such a large gape? According to the authors, one possibility is that a large mouth allows the birds to hyperventilate at the nest, where temperatures often exceed 45°C. In contrast, temperatures at A. pomarina nests are usually under 35°C. Another hypothesis is that the differences in gape size are related to the type and size of prey. Whatever the reason, the gape of Aquila hastata has not only helped restore it to species status, but should also aid in the field identification of this species in all plumages. The gape of hastata extends well behind the eye, whereas that of clanga (and pomarina) does not. So if you see a spotted eagle, and manage to get close enough, you may very well find that you are looking at Aquila hastata, an endemic of the Indian region and freshly restored to species status.
BIRD IN G N O T ES Com piled by A asheesh Pittie
This column publishes notes in brief telegraphic form, from Andhra Pradesh, Delhi, Goa, Haryana, Karnataka, Kerala, Maharashtra, Punjab, Rajasthan & Tamil Nadu on interesting and significant sightings and behaviour like breeding, feeding, migration, nesting, etc. Notes on threatened birds are also welcome. Their status ‘*’ follows BirdLife International (2001) Threatened Birds of Asia. English names, sequence and scientific nomenclature follow Manakadan & Pittie (2002): Standardised English and scientific names of the birds of the Indian Subcontinent. Newsletter for Birdwatchers 42(3): i-viii, 1-36. Unless specified, all observations are for 2002. Abbreviations, Contributors, Notes, Regional Referees, etc., are at the end. For selection of breeding criteria 'Probable, Possible, Confirmed', see Pitta # 82, February 1998, p. 4.
A N D H RA PRA D ES H 11.x: SPOT-BILLED PELICAN VU* 120; DARTER NT* 4; BLACK- CROWNED NIGHT-HERON 300; ASIAN OPENBILL-STORK 8,000, CB, 800 N; GLOSSY IBIS 700; ORIENTAL WHITE IBIS NT* 1,200. GUNTUR DISTRICT Ramchandrapalem (Garapadu) [K. Mrutyumjaya Rao] MEDAK DISTRICT 10.viii: ORIENTAL WHITE IBIS NT* 350. ICRISAT Campus (C.T. Hash) Uppalapadu (K. Mrutyumjaya Rao & Ramana Kanaparthi) 27.x: BLACK-CROWNED NIGHT-HERON CB, ad., & imm.; COMB 2.viii: SPOT-BILLED PELICAN VU* 21; DARTER NT* 8; BLACK- DUCK; SPOT-BILLED DUCK CB, ad., with yng.; NORTHERN CROWNED NIGHT-HERON 300; ASIAN OPENBILL-STORK 8,000, SHOVELLER 1,000+; NORTHERN PINTAIL; MARSH HARRIER; N activity; ORIENTAL WHITE IBIS NT* 1,800. GREATER SPOTTED EAGLE VU*, 2 juv.; COMMON KESTREL; 10.viii: BLACK-CROWNED NIGHT-HERON 300; ASIAN INDIAN PEAFOWL CB, ad., with imm., M in non-br., plm.; OPENBILL-STORK 8,000, CB, 1,000+ N; ORIENTAL WHITE IBIS SPOTTED REDSHANK; COMMON GREENSHANK; COMMON NT* 2,000, CB, 150+ N. SANDPIPER; BLUE-TAILED BEE-EATER; EUROPEAN ROLLER; —7—