Studies of less familiar 161 Booted R. F. Porter Photographs by Pierre Petit, M. D. England and A. N. H. Peach Plates j 2- j 8

The Booted Eagle Hkramtus pennatus is a small eagle similar in size to a Buzzard Buteo buteo, but of slimmer build, with narrower wings and a longer tail. In flight its proportions are not unlike those of a Mikus migrans, though the tail is square-ended, not forked (plate 58). When perched, its long feathered tarsi, or 'boots', are characteristic (plate 53b). The is dimorphic, a feature which, among European birds of prey, it shares only with Eleonora's Falcon Fa/co eleonorae. Many raptors show considerable variations, but in most cases these take the form of clines from very pale to very dark through a whole range of intermediates. The Booted Eagle has two very distinct phases—a light and a dark. This dimorphism is exhibited by both sexes; breeding pairs frequently consist of one dark and one light and their offspring may be either light or dark. Both phases are brilliantly illustrated in plates 52-58. The light phase has a lightly streaked tawny-rufous head and neck, with a white forehead and superciliary stripe and dark tawny-brown ear-coverts and cheeks. The under-parts are white with rufous streaks on the chin, upper breast and flanks (plates 5 5 a and b), and the under wing-coverts are also white with brownish flecks (plate 5 8b). Im- matures look more 'gingery' below. The white under-parts extend on to the 'shoulder' to form a white patch (especially plate 5 2). The mantle and back are dark brown, with blackish primaries and secondaries, and there is a conspicuous broad bar of pale huffish-brown on the upper wing-coverts and scapulars, giving the upper-parts the appear­ ance of a well-marked Black Kite (plate 52 again). The upper tail- coverts are pale buffish-brown, contrasting with the brown back and brown tail; the latter is faintly barred with grey. The under tail- are white with a varying amount of dark smudgy grey on the tips, particularly of the central feathers. The upper-parts of the dark phase (plates 54a and b) are similar to those of the light phase, but the under-parts (plates 54c and 55 c) are wholly dark brown, streaked with black, though the bases to the primaries are paler brown and the under-tail is also paler, frequently taking on an orange tinge. The white shoulder-patch can occasionally be discerned in the field (plates 54a and 5 5 c), In flight at long range, light-phase Booted show a conspic- 353 334 Booted Eagle studies uous under-wing pattern of white forewings contrasting with black flight-feathers, not unlike the pattern of an adult Egyptian Vulture Neophron percnopterus (plate 5 8b); despite their differences in shape and structure, I have seen these two species confused more than once. Dark-phase birds can be more easily overlooked, particularly among flocks of Black Kites. To some extent they also resemble brown Marsh Harriers Circus aeruginosus, though the wing position when soaring is quite different: the Booted Eagle holds its wings level, not in the shallow ' V of the harrier. From beneath, both phases show a paler area on the inner primaries and outer secondaries (plate 5 8), but a much more elusive character (just discernible in plates 58a and 5 8d) is the translucent whitish trailing edge to the wings and tail, sometimes visible when overhead in bright sunshine. The wing-beats are deeper and more floppy than those of Buz2ards and are interspersed with glides on level wings. The breeding distribution of the Booted Eagle was described in detail by Vaurie (1965) and Dementiev and Gladkov (1966). In western it is confined to Spain, Portugal, central and north-east France and the Balearic Islands, and in the east to Hungary, Jugo­ slavia, Albania, northern Greece, Bulgaria, Romania and European Russia almost as far north as Moscow. Its range extends along the north coast of Africa from Morocco to Tunisia, and in southern Asia from Turkey, northern Syria and the Caucasus through northern Iran to Afghanistan and north-west India, as well as the Turkmen, southern Uzbek, Tadzhik and Kirghiz Republics north-east to the region of Lake Balkhash. In central eastern Asia it occurs again in the northern Altai Mountains, northern Mongolia, the Sayan Mountains and the Irkutsk region eastwards beyond Lake Baikal to northern Manchuria. Thus this eagle is distributed in three main regions: western Europe and north-west Africa, eastern Europe and southern Asia, and northern Mongolia and the Lake Baikal area. At its broadest the range extends south to 55°N and north to 5 j°N. Systematists differ on the degree of subspeciation involved over this range of 7,000 miles from west to east. Vaurie (1965) treated the species as monotypic, but B. Stegmann (Orn. Monatsber., 43: 151) separated the population of southern Siberia and northern Mongolia as H. p. harterti (with which H. p. milvoides and H. p. albipectus are synonymous). Brown and Amadon (1968) also split the species into two races. Whatever the conclusion, the fact remains that in the east of the range are longer-winged and migrate to Malaya, Burma and India, while those in the west migrate to north­ east and tropical Africa. There does not appear to be any clear geo­ graphical distribution of the light and dark phases throughout the range (Dementiev and Gladkov 1966), though there is a tendency to find a higher ratio of dark birds in the east. From observations of Booted Eagle studies 335 migrants in Turkey, and in particular at the Bosphorus, it would appear that the Booted Eagles of eastern Europe are largely of the light phase (of the order of 75 %). As with nearly all raptors, the Booted Eagle is decreasing in numbers. In France the population has been estimated at only 30 to 50 pairs and steadily decreasing; in Portugal it is 'scarce' and in Spain 'thinly spread' (I.C.B.P. 1964). At the Bosphorus 260 migrants were counted between 1 ith August and 9th October 1966, and similar totals in 1967, 1968 and 1969; a century ago, however, A. Alleon and J. Vian recorded flocks of several hundreds passing in rapid succession (Porter and Willis 1968). In Russia Dementiev and Gladkov (1966) recorded a decline in the population of the Kharkov region and indicated that changes in habitat were responsible. The breeding areas include deciduous or coniferous woodland from well-forested areas to scattered clumps of trees and from sea-level up to 10,000 feet. The preferred habitat, however, seems to be wooded slopes with open glades and adjacent open or cultivated areas in the foothills of more mountainous regions. Forest clearance throughout Europe and Asia must have had an adverse effect on the population. In addition, the habitual shooting of birds of prey throughout much of their range, particularly in the countries through which they migrate, must have taken a considerable toll. In the three countries of western Europe where Booted Eagles nest—Spain, Portugal and France—the species is not protected. Even if protection were afforded to it, enforcement would be impossible without protection of all other birds of prey, for how many members of the shooting populace could distinguish between, say, a Buzzard and a Booted Eagle? On migration in Europe, Booted Eagles can be most easily observed at the Bosphorus and Gibraltar. Spring migrants start to arrive in late March and the peak generally occurs in the first two weeks of April, though migrants (possibly non-breeding birds) can still be seen on passage in late May. In autumn the peak occurs in the middle weeks of September, and at the Bosphorus it coincides with the peak passage of Lesser Spotted Eagles pomarina and Buzzards. In both spring and autumn my own observations have been of single birds, or occasi­ onally of groups of up to three. In Europe Booted Eagles start to take up their territories in mid- April. As with most birds of prey, the nuptial display-flights are spectacular and the birds are then extremely vociferous. Booted Eagles which I watched in Istanbul's Forest of Belgrade were far more active and spent longer on the wing than the other nesting raptors of the area. The most frequent display consists of a series of steep undu­ lations with the wings held close to the body. This is performed by both sexes and the position adopted is similar to that in plate 58c, which shows one diving towards its prey, in this case a sparrow 336 Booted Eagle studies Passer sp. Sometimes one of the pair turns on to its back in mid-air and presents upstretched claws to its mate. During these nuptial aerobatics the call I have heard is generally a rather querulous kvee-kvee- kvee, uttered by both birds, though clearly from Dementiev and Gladkov (1966) and Brown and Amadon (1968) there are many variations of this. Both at the breeding grounds and on migration, their great agility and rapid manoeuvrability are seen at their best when being mobbed by or mobbing other birds, particularly raptors, and one gains the distinct impression that Booted Eagles indulge in these aerial forays as much for their own sake as in guarding a territory. When being mobbed, the may rapidly gain speed with deep, powerful, wing-beats and then suddenly roll over sideways flinging its talons into the air at its pursuer. It will then right itself and continue leisurely as if nothing had happened. The aerobatic skills of this eagle can also be appreciated when it is hunting: Meinertzhagen (1959) gave perhaps the most vivid descrip­ tions of Booted Eagles after prey. They feed mostly on small to medium-sized birds, including Partridges Perdix perdix and Turtle Doves Streptopelia turtur, and on small and such as the Suslik Citellus citellus, probably one of the most conspicuous rodents over large areas of their breeding range. They capture prey by a lightning swoop on to the ground or into a tree (plate 58c), and will twist and turn with great agility through branches and foliage in pursuit. They often hit the ground with great force when chasing grounded birds and mammals, and at such times show complete disregard for any human beings near-by. The nest is built well up in a tree, either deciduous or coniferous; occasionally the pair will add material to the old nest of another instead. In north Africa the species is said to breed on rocky crags (Brown and Amadon 1968). The nest is a large structure, often measuring four feet across and two feet deep, though the cup is shallow, as can be seen in plate 5 6 where the is also visible. It is frequently—perhaps always—adorned and lined with fresh foliage (see plates 56 and 57) which stains the eggshells, initially almost always white, until they become blotched and spotted in various shades of brown; true pigmentation of the , in the form of rusty spots and streaks, is very rare indeed (Blair 1964). Booted Eagles normally lay two eggs, sometimes only one and rarely three, at intervals of two to four days. In Europe egg-laying takes place in late April or May. The breeding habits have been poorly studied, but incubation, by the female alone, lasts about a month and the young spend some nine weeks in the nest (Dementiev and Gladkov 1966). Throughout this period the male does most, if not all, of the hunting and brings food back to the sitting female and their growing young. The whole process from the onset of incubation to the first precarious Booted Eagle studies 337 flights of the young bird (I use the singular as, in common with many other eagles, normally only one reaches the flying stage) takes about three months. In conclusion, some notes on the photography. Pierre Petit took his remarkable series over five successive Augusts, when the young (after fledging in late July), and more rarely the adults, perch for long periods on dead trees. Plates 52, 53b and 5 5b were taken at 9-10 metres and the rest of plates 53-5 5 at 19 metres, using a 400 mm lens and in 1966 a 640 mm one. Mr Petit regards the bird on plates 5 3a and 5 5a as an adult and the others as four different juveniles. (The flight photos may relate to other individuals as three pairs bred in the area each year.) There is much variation, but he considers light adults to have darker faces than the young, and whiter, less rufous under-parts with more distinct streaking, though sometimes only their worn plumage distinguishes them. Dr Geoffrey Beven has provided notes on the nest on plates 5 6 and 57. Found in south Spain on 21st May 1970, it was photographed by Dr A. N. H. Peach on 30th May and by M. D. England during early June. The habitat was a steep-sided wooded valley in mountain country. Most of the trees were well-spaced cork oaks Quercus suber with tall heath and bracken in between, but the nest was in another oak, Q.faginea. Because of the slope, the nest was 3 3 feet from the foot of the tree but 40 feet above the ground directly below. It was four feet across and made of sticks and branches, some more than an inch thick and quite heavy. It appeared to be an old nest partly reconstructed: there was a large hole towards one side and the eagle had apparently reshaped the rest of the old cup into a new one. It was lined with old leaves, but there were fresh green ones all round the edge. The single egg was dirty white with no markings, but became stained fawn or pale brown. The presumed female (plates 5 6 and 5 7) was light-phase and the male dark. Unfortunately she was not seen at the nest after nth June and it was concluded that the egg was probably addled.

REFERENCES BLAIR, H. M. S. 1964. 'On the oology of the Booted Eagle'. Ool. Rec, 38: 61-63, BROWN, L., and AMADON, D. 1968. Eagles, Hawks and Falcons of the World. Feltham. Middlesex, vol 2: 680-681. DEMENTIEV, G. P., andGLADKOv, N. A. 1966. Birds of the Soviet Union. Israel Program for Scientific Translations, Jerusalem, vol 1: 524-329. I.C.B.P. 1964. Report on the I.C.B.P. Working Conference on Birds of Prey and Owls. London. MEINERTZHAGEN, R. 1959. Pirates and Predators. London and Edinburgh. PORTER, R., and WILLIS, I. 1968. 'The autumn migration of soaring birds at the Bosphorus'. Ibis, no: 520-536. VAURIE, C. 1965. The Birds of the Palearctic Fauna. London, vol 2: 181-182.

R. F. Porter, R.S.P.B., The Lodge, Sandy, Bedfordshire PLATE 52. Light-phase Booted Eagle Hieraaetuspennatus sunning its wings, France, August 1968. Note the broad huffish band across both wing-coverts and scapulars (recalling a Black Kite), the pale tail-coverts, and the white shoulder patches that extend back from the light under-parts (pages 333-337) {photo: Pierre Petit)

PLATES 5 3 and 54. Left, light-phase Booted Eagles, France, August 1967 and 1968: note the 'booted' legs and pale under-parts. Above and below, two dark-phase ones, August 1965 and, below right, 1964: they are similarly patterned above but darker, and wholly dark brown streaked with black below (page 333) {photos: Pierre Petit)

PLATE 5 5. Two light-phase Boc ted Eagles, France, August 1966 and 1968, and a dark-phase, August 1965. The light-phase vary ;n tne colour of the face, the amount of streaking below and the degree of contrast in the wing-coverts (cf. plate 5 5 too) this may be due to age (page 537) or to individual variation. Their whitish under-tail with an ill-defined darker tip is a flight character better shown here than in plate 58. The pale primaries on the dark-phase are a trick of sunlight, but note there is still a white shoulder patch {photos: Pierre Petit) PLATES 56 and 57. Light-phase female Booted Eagle at nest with one egg (visible below), Spain, May-June 1970. Two eggs are more usual and this one may have been addled (page 337). This nest, forty feet above sloping ground in an oak, was some four feet across and made of sizable sticks with a shallow cup of old leaves and new greenery round the edge {photos: M. D. England and, lower right, A. N. H. Peach)

PLATE ;8. Top three, light-phase Booted Eagles (one diving at a sparrow), France, August 1966, and lower two, dark-phase, August 1964. The light-phase is patterned like an Egyptian Vulture, while the dark-phase resembles a Black Kite but with an unforked tail looking dirty orange in strong sunlight. Note the pale wedge between primaries and secondaries in both phases and the thin white trailing edge to wings and tail, faintly visible in the two on the left (page 334) {photos: Pierre Petit)