Delic & Muzinic:Booted © Eagle Ornithologische in Croatia Gesellschaft Bayern, download unter www.biologiezentrum.at 219 Orn Verh. 25: 219-222 Breeding of the Booted Eagle Hieraaetus pennatus in North-Western Croatia Zwergadler-Brutvorkommen in Nordwest-Kroatien By Antun Delic & Jasmina Muzinic 1. Introduction Although the Booted Eagle,Hieraaetus 1985). However, these data may insufficient pennatus, is a Mediterranean species (Ruc- to characterize the real state of the species’ ner 1968) it occurs as a breeding bird more distribution. frequently in the Southern and eastern parts A young Booted Eagle was found in the of the Balkan Peninsula than in Croatia Bilogora Mountain in Northwestern Croa­ (MATVEJEvet al. 1973). In Croatia the Booted tia at the utmost western fringe of its main Eagle is considered to be a breeding species breeding ränge in the East (Voous, 1960). only in Slavonia (= Slavonija, north-eastern The data concerning this record are pre- Croatia) (M atvejev et al. 1973; V asic et al. sented in this paper. 2. Area and Circumstances Bilogora is an elongated, wooded moun- The area where the bird was found is not tain ränge in the north-western part of settled by people, and the nearest village is Croatia (Fig. 1). It stretches from Kopriv- Turcevic Polje, about 2 km away in the bee nica on the west to Miokovicevo in the east. line. The highest peak of Bilogora is Rijeka, 307 The young Booted Eagle was found on m above sea level. 25th September 1992 by a forester. It was a A Booted Eagle nestling was found in thesunny and quiet day (the summer of 1992 is Veliki Rastovac Forest on the eastern slopes considered the hottest summer in the past of Bilogora at 232 m above sea level. The six years). The bird was kept alive for 45 forest is comprised of Durmast Oak and days. It did not take food, and was therefore Hornbeam, Querco-carpinetum ülyricum crammed. The first days it was on fish, later Horv. 1938, andabout 80years old. Inplaces on house mice and house sparrows. Some there are groups of Beech,Fagus sylvatica, biometric data were taken. and Lime,Tilia sp., as well as some single The Booted Eagle nests in trees(P errins , Common Maple, Acer campestre, and Bird 1987), and they eyrie should have been Cherry, Prunus avium, trees; in the lower placed in a treetop nearby. The area was parts there are also Common Oak, Quercus examined on 16th January 1993 in order to robur, trees. Gornje Poilovlje, the area find the nest. towards which the eastern slopes of Bilogora gravitate, is a rieh habitat f or birds (D elic, 1988). 220 Orn. Verh. 25, 1995 © Ornithologische Gesellschaft Bayern, download unter www.biologiezentrum.at Fig. 1: Breeding locality (cross-marked circle) of the Booted Eagle in Bilogora Mountain in north-western Croatia. - Fundort (Kreis mit Kreuz) des Zwergadlers im Bilogora-Gebirge in Nordwest-Kroatien. 3. Results The Booted Eagle was found on the forest were dark brown with white tips appearing ground. Obviously it was in a good con­as white spots; the under wing-coverts were dition when it was found. It tried to fly off,white, while the primaries were black- but it was unable to rise in to the air. The brown with a narrow white edge at the tips; bird was just acquiring its juvenilethe forehead was white and the crown plumage. It was identified as a Booted streaked with brown; the supercilium and Eagle, Hieraaetus pennatus, and its age was the lore were blackish, surrounding the eye; established as a two-month-old nestling the iris was dark grey; the bill was black, according toP orter et al. (1981). Its length while the cere and the gape were yellow; the was 520 mm and its weight 710g; the length foot was yellow and the claws black. of its wings was 394 mm. On 16th January 1993 the bird’s nest was During its stay in captivity the bird found at a distance of about 300 m from the acquired its full juvenile plumage. Cheekplace where the young had been found. It and throat were yellowish-white; the nape had a diameter of about 1 m, and it was was yellowish-white with dark brown placed on the forked branch of a beech tree feathers in places; the breast, belly and at a height of about 20 m. The circumference flanks were yellowish-white with sparsely of the tree trunk was 28 cm. elongated streaks; the upper wing-coverts 4. Discussion M atvejev et al. (1973) mention the Booted data on nesting locations, breeding season, Eagle as a breeding bird in the Slavonian or the number of pairs.V asic 5 et al. (1985) part of Croatia, but they do not provide any mention only (probably to protect the nest) © Ornithologische Gesellschaft Bayern, download unter www.biologiezentrum.at Delic & Muzinic:Booted Eagle in Croatia 221 that nesting of the Booted Eagle was terranean area. There are no data in general recorded in Slavonia in 1981. The finding ofon the biology and ecology of populations in a young in the north-western part of the eastern/Mediterranean part of Europe. Croatia is the first proof in this area. The Booted Eagle is known to be M uzinic et al.(1922) consider the Booted dimorphic with regard to plumage and Eagle to be a rare breeding bird in Croatia. occurs as a pale morph or a dark morph. The The young found on Bilogora was rearedmorphological description of the juvenile by its parents, but for unknown reasons itbird that was found conforms to the found itself outside the nest on the ground,description of the pale morph given by before becoming fully fledged. In the case of Cramp & S immons (1979) undP orter et. al. the Booted Eagle two chicks often hatch, (1981). but it is rare for both to be reared since the The Booted Eagle, as a bird of prey, builds brood is often reduced to one. One chicka relatively small nest on tall deciduous survives in the nest and stay in(C itramp & trees (Voous, 1960), but often uses the nests S im m ons , 1979). Since the specimen was of other birds. It may, therefore, be con­ found as a two-month-old nestling, it maycluded that the nest with a diameter of 1 m be concluded that it was hatched aroundwhich was found in a beech tree aboout 300 25th July 1992. m away from the place where the young Incubation lasts 35 (36)-38 days (Bou- Booted Eagle was found on the ground was cher , 1978; P errins , 1987), so it may be its nest. The finding of the nest makes presumed that the eggs were laid aroundbreeding of this species in the eastern June 20th. 1992, indicating late breeding. Bilogora area even more likely. The Booted Eagle populations of the Veliki Rastovac Forest on Bilogora is a countries of the formerU S S R are late typical habitat of the Booted Eagle which, breeders (Cramp & S im m ons , 1979) but there according to Voous (1960) looks for deci­ are no exact data on when the Booted Eagle duous and mixed woodlands in valleys and starts breeding in the Eastern Medi­ on low mountains. Summary Breeding of the Booted Eagle,Hieraaetus of Croatia. The specimen was a pale morph. The pennatus, was proved for the Veliki Rastovac bird was found as a two-month-old nestling fal­ forest on the eastern slopes of Bilogora Mountain len to the ground. This age indicates the in north-western Croatia in 1992. This is the first beginning of breeding around the 20th June, record for the nesting of this species in this part 1992, which is quite typical for late breeders. Zusammenfassung Brut des Zwergadlers,Hieraaetus pennatus (Gmelin) 178 8, in Nordwest - Kroatien Im Jahre 1992 wurde der Zwergadler im Wald­im Alter von etwa zwei Monaten. Das geschätzte gebiet von Veliki Rastovac im Ostteil des Alter läßt auf einen Brutbeginn um den 20. Juni Bilogora-Gebirges in Nordwest-Kroatien als schließen, einem relativ späten Datum. Bisher Brutvogel angetroffen. Dieses ist der erste Nach­ galt der Zwergadler nur als Brutvogel im öst­ weis der Art in diesem Teil Kroatiens. Es handelt licher gelegenen Slawonien. sich um den Fund eines nichtflüggen Jungvogels 222 Orn. Verh. 25, 1995 Literature B o u c h e r , M. (1978):© Birds Ornithologische of Prey Gesellschaft of Britain Bayern, download and unterP e rwww.biologiezentrum.at r in s , Ch. (1987): Birds of Britain and Europe. Europe. Hamlyn, London-New York-Syd- D. Attenborough (ed.). ney-Toronto. P o r t e r , R. F et al. (1981): Flight Identification of C r a m p , S. & S im m o n s K. E. L. (eds., 1979): the European Raptors. T. & A. D. Poyser, Berk- Birds of the Western Palearctic. Vol. II, 251- hamsted. 258. Oxford University Press, Oxford. R u c n e r , R . (1968): The Relationsip Between the D e l ic , a . (1988): Ptice mocvarice ribnjacarstva Mediterranean Vegetation and Mediterran- „Koncanica“ Larus 40: 25-33. ean Elements of the Avifauna of the Balkan M a t v e j e v , S. & V a s ic , v . F. (1973): Catalogus Peninsula. Larus 16-18: 79-105. faunae Jugoslaviae. 4/3 Aves. ConsoliumV a s ic , V F. et al. (1985): The Status of Birds of Acad. Sei. et Art. R.B.S.F.J. Ljubljana. Prey in Yugoslavia with Particular Referen­ M u z in ic , J. & M ik u s k a , J. (1992): Ptice Hrvatske.