Separation of Tawny Eagle from Steppe Eagle In
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Notes Separation of Tawny Eagle from Steppe Eagle in Israel Tawny Eagle Aquik rapax generally looks smaller and rather puny (and also, when perched, less elongated/horizontal) compared with Steppe Eagle A. nipaknsis. Diagnostically, the North African race A. r. belisarius differs in all plumages from Steppe in being smaller, in having die creamy-white of the uppertail- coverts extending well up onto the upper back (on Steppe, usually restricted to uppertail-coverts, lacking on rump and only indistinct on lower back), in showing a conspicuous sandy wedge on the inner primaries below (generally indistinct or absent on Steppe) and, in juvenile/immature plumages, lacking Steppe's whitish underwing-band; the remiges and rectrices are usually finely barred or almost unbarred compared widi corresponding plumages of Steppe. The general coloration of Tawny's body and underwing-coverts is pale tawny or bufEsh-yellow to pale foxy/rufous (or dark greyish-brown, but this is virtu ally confined to more soumerly populations/races), contrasting highly widi the remiges and rectrices: more or less reminiscent of the underpart pattern of juvenile Imperial Eagle A. heliaca, but unstreaked. The mantle, scapulars and upperwing-coverts are also distincdy tawny-sandy, but with the feathers dark- centred (chiefly on greater coverts, tertials and lower scapulars). In good views, mainly when perched, Tawny normally shows a slighdy shorter gape line, ending level widi the centre of die eye (reaches rear edge on Steppe); die adult's iris is yellowish-brown (dark brown on Steppe). In flight, compared wim Steppe, Tawny has broad and short wings with ample 'hand', and shows a well-protruding head and a relatively short and more square-ended tail; in active flight, it is rather stiff-winged with more rapid wingbeats. Tawny is radier noisy, giving 'kah' or 'kowk-kowk' calls (Steppe is predominanuy silent on passage or in winter). The above description summarises die principal features by which die first Tawny Eagle for Israel, in November 1992 in die Negev (Brit. Birds 87: 5), was identified; see also accompanying plates 102-107. HADORAM SHIRIHAI PO Box 4168, Eilat 88102, Israel The author welcomes comments and any relevant material, including photographs, on the entire rapax-nipalensis complex in Africa and Asia for possible future publication in these pages. These should be sent to HS at the address above. EDS 102-107. Facing page: three left-hand plates, adult/subadult Tawny Eagle Aquila rapax, northwest Negev, Israel, November 1992; three right-hand plates, Steppe Eagles A. nipaknsis, Eilat, Israel, springs 1985-88: top, adult; centre and bottom, immature, probably second-summer (H. Shirihai) 396 398 Notes Identification of Parrot Crossbill The influx of Parrot Crossbills Loxia pytyopsittacus into Britain during the late autumn of 1990 gave many observers their first opportunity to test out the identification lessons learned during the previous influx, in 1983-84, and subsequent breeding. In late November 1990, a number of sites in northeast England were found to be holding Parrot Crossbills, and one of these, at Heavygate Farm, Chopwell Woods, Tyne & Wear, presented the opportunity for close-range study and mist-netting. Between 20th November and 5th December, eight individuals were caught and ringed at tiiis site by the Durham Ringing Group and many more were observed at close quarters, sometimes for prolonged periods. The following notes summarise some of our observations, especially where they differ in certain details from previously published information. Bill In the field, the most useful identification criterion was undoubtedly the size and shape of the bill (particularly well described by Harris et al. 1990), especially the bulging lower edge of the lower mandible, and die apparent 'stubbiness' (i.e. the ratio of depdi to length) of the bill in relation to die depdi of the head, diis stubbiness being enhanced by die mandible tips projecting less compared with those of Common Crossbill L. curvirostra. Attention has previously been drawn to the obvious pale cutting edges of the mandibles, but this feature should be used only with care as Common Crossbill can also show very obvious pale areas on the mandibles (see plate 109). The shape and extent of the pale area, however, can be distinctive on Parrot Crossbill, tending to expand out from the middle of the cutting edges to form two half- moons, deepest and broadest on the lower mandible, but not usually reaching to die tips of the mandibles (plate 108), whereas those on Common Crossbill, if present, tend to reach the tips (plate 109). 108 & 109. Left, male Parrot Crossbill Loxia pytyopsittacus and, right, male Common Crossbill L. curvirostra, Tyne & Wear, December 1990 [Stephen Westerberg) General shape The head and neck of Parrot Crossbill are massive and, although the lengdi of die head from front to back is not that much greater tiian on Common Crossbill, its breadth is significandy greater. This gives Parrot Crossbill a much more square-headed shape, appearing especially flat- topped in comparison with Common's more domed crown (some extreme Parrot Crossbill skins examined at die Hancock Museum, Tyne & Wear, had heads almost 33% broader than similar skins of Common). A noticeable feature of the birds at Heavygate, and readily apparent in some of the photographs, was that Parrot Crossbills, in profile, often seemed to possess a Notes 399 slight but distinct 'forehead step' between the top of the head and the proximal end of the upper mandible. This feature, not usually so apparent on Common Crossbill, is due to the Parrot Crossbill's culmen jutting out more or less horizontally from the forehead area. The arc of Common Crossbill's more rounded head profile runs down relatively smoothly into the more even curve of the culmen, creating a less obvious, or much more subtle, step. Parrot Crossbill is heavy and 'hulk-like' at its front end, wim an extremely muscular neck (this is very obvious to a ringer when one is in his grip), and is thin, relatively weedy, and attenuated at the rear. Common Crossbill presents a much more 'balanced' shape, undoubtedly bulky but, unlike Parrot, not disproportionately so. Body bulk A feature which we feel has been too quickly dismissed in the past (though it was highlighted by Millington & Harrap 1991), and which is the first thing likely to draw the observer's eye to a single Parrot Crossbill in a flock of Commons, is the marked size difference between the two species. Catley & Hursthouse (1985) mentioned that Parrot Crossbills have been noted as appearing some 10% larger than Common Crossbills, akhough, from our small sample, we consider this perhaps an understatement. The smallest Parrot Crossbill caught at Chopwell was 25% more massive man the largest Common Crossbill trapped at the same site, and it should be noted mat the latter was a large individual, with a wing length greater than the upper limit given by Svensson (1984) for the species. The largest Parrot Crossbill handled at Heavygate Farm was over 40% heavier than this Common Crossbill. This is a significant difference in bulk, being greater than the average difference between Blackbird Turdus meruk and Song Thrush T. phihrmhs or between Blue Tit Parus caerukus and Coal Tit P. ater. It must be remembered, however, that the Parrot Crossbills at Chopwell may have been settled for some time, allowing mem to replenish fat and body muscle, which would be reduced in a newly arrived coastal migrant and therefore reduce its total bulk. A much wider variation in mass was noted for bodi crossbill species on Fair Isle, Shetland, where migrants do not have such a ready supply of food as was available in Chopwell Woods. So, although a large degree of caution does need to be exercised when using size as an identification feature, it is probably more useful than has been stated previously. Biometrics Earlier works have claimed that Parrot Crossbill looks 'long- winged' in comparison with Common Crossbill. While mis may be the case in some instances, it is by no means the whole truth. Indeed, from our experience of Common Crossbills handled and observed during that species' influx in 1990, we would suggest that under certain circumstances, and with certain populations of Common, die reverse may be true. The longest-winged Common handled at Fair Isle Bird Observatory during the 1990 influx had a wing of 107 mm, weE outside Svensson's (1984) published range for this species and equivalent to the longest-winged of the Parrot Crossbills handled at Heavygate. Birds wim such long wings, wim shorter tails and lacking the bulk of Parrot Crossbill appear proportionately much longer-winged than Parrot, as the wingtip falls much farther down the tail than on the latter. Some large crossbills caught on the East Coast during die period of the influx were reported (W. E. Oddie in litt) to be causing identification problems 400 Notes in the hand. These difficulties no doubt arose from Svensson's (1984) emphasis on measurement of key characteristics such as bill depth and wing length. Too firm a reliance on biometrics, however, may indeed cause problems when extremely large Common Crossbills, or small Parrot Crossbills, are encountered. An individual trapped on Fair Isle in September 1990 is a case in point: its bill depth of 13 mm was too small for Parrot Crossbill and its wing measured only 104 mm (3 mm shorter than that of the largest Common Crossbill measured at the Observatory that summer, and equalling the wing length of the longest-winged Common caught at Heavygate); the 'sinusoidal' lower-mandible shape, the thick-necked bulk of the bird and several other characteristics, however, led to identification as Parrot Crossbill (P. V. Harvey & N.