LEGGED BUZZARD &Lpar

LEGGED BUZZARD &Lpar

]. RaptorRes. 21(1):8-13 ¸ 1987 The Raptor ResearchFoundation, Inc. NOTES ON THE BREEDING BIOLOGY OF THE LONG-LEGGED BUZZARD (Buteorufinus) IN BULGARIA ILIYA Ts. VATEV ABSTRACT.--Observationswere madeon Long-leggedBuzzard (Buteorufinus) nests in Bulgariabetween 1978-83. Egg hatchinginterval was 29-44 hr. First nestlingplumage color was dirty-white tingedbeige, cere and legs yellow; iris color changedfrom sepia at hatchingto brownish yellow-greyat fiedging. Featherswere visibleby two wk. Until two wk old, nestlingsassumed a "frozen" postureon their bellies when alarmed. Nestlingsfed unaided by the fourth wk. Fledging beganby d 49. Adults were aggressive towards humanswhile young were downy, but aggressionlessened as young got older. The Long-leggedBuzzard (Buteorufinus) is one openplains beyond. The area is grazedby sheepand cattle of Europe'sleast studiedraptors. Little detailedin- attendedby herdsmen.The landscapeis variedby scattered thorn scrub,streamside willows (Salix sp.), Carpinusorz- formation on the breeding cycle of the speciesis entalisand a smallconifer plantation (Pinus nigra). Nearest availablein the literature, especiallywith regard to arable groundis one km away. Climate is temperatecon- its nestlings(Dementiev and Gladkov 1954; Brown tinental; av. rainfall = 592.1 liter/m 2 (1981-84); alti- and Amadon 1968; Glutz et al. 1971; Harrison 1975; tude -- 7-800 m. Cramp and Simmons1980). Recently,Michev et al. RESULTS (1984) reported14 definitebreeding records for Bul- The Nest. Long-leggedBuzzards used the same garia and estimatedthe country'spopulation to be nest at Pekliuka in 1981, 1983, and (T. Michev, around 50 pairs. Also reported were noteson nest pers. comm.) 1984. A new nest, relatively slight in sites,egg size, breeding season and foodof the species. construction, was used in 1982 on the same cliff Herein, I report new data from Bulgaria on de- complex approximately 350 m from the old nest velopment and morphology of young, including (Fig. 1). Each nestwas 50-60 cm dia, and bothwere hatchinginterval, weight at hatching,coloration of situated on small cliff ledges. The older nest was iris, bill, cere and legs, and growth of down and 33-46 cm deep, and the newer nest measuredonly feathering.I also report on the behaviorof adults 20 cm deep. Sticks measuring <2.5 cm composed and young and on certain other aspectsof Long- the baseof the nest,while thosein the upper layers leggedBuzzard breedingbiology. were smaller. The nest cupswere < 10 cm deep and STUDY AREA AND METHODS were composedof soft, fibrous, woody materials. Data were collectedon the nestingof the Long-legged Within the nest cup was found a tuft of grassroots, Buzzard from 1978-83 during visits to five more easily partsof a paper napkin, and bits of rusty wire. accessiblenests. Four nestswere in South Bulgaria and Basedon plumage,at least one of the adults at one in North Bulgaria. Three nestswere visited episodi- cally (exceptfor the nestsin Pekliuka area). Most obser- the Pekliuka site was judged to be the same indi- vations of nestlings were made at cliff-nests of a pair vidual in all four yr. The bird wasthe slightlylarger breedingin the Pekliuka area near Slivnitza(Sofia district) one in all pairings and was thus consideredto be during 1981-83. Dates of visitswere as follows:9 April, the female, although differencesin size were mini- 3, 14 and 16 May, and 4 June 1981; 23 May and 13 June mal even when pairs perchedclose together. 1982; daily during the hatch (1-4 May) and weekly on 11, 18 and 25 May and 2 June, with visits also on 21 The Eggs.A newly laid eggweighed 70.4 g and May, and 18 and 21 June 1983. Photographswere taken measured63.7 x 46.2 mm. An addled egg found and specimensof vertebrateprey were collectedfrom the duringthe ringingof youngon 13 June 1982 weighed nestsfor identificationon eachof the weeklyvisits. On 11 61.5 g and measured60.3 x 47.5 mm. and 21 May 1983 the nest was watchedfrom a distance of approximately800 m to record arrival times of adults Hatching and Growth of Young. On 1 May with food. On 4 June 1981 the nest was watchedbetween 1983 one adult buzzard broodedtwo young,already 0930-1900 H from a hide situated 25 m away. More of different sizes and in first down, and two eggs. frequent visitsto the nestwere avoided.Time spent at the The situation was unchangedthe following day at site was reduced to a minimum to avoid disturbance, as 1300 H and 1800 H. A third youngwas in the nest the speciesis included in the list of endangeredEuropean birds (Hudson 1975; Michev 1986). at 0900 H on 3 May, and a fourth nestling'sbill The Pekliuka nest was situated on a small, limestone was protruding from the eggshellat 1200 H on 4 outcropin a shallowvalley surroundedby low hills with May (Fig. 2). Part of the fourth nestling'shead SPRING 1987 LONG-LEGGED BUZZARD BREEDING BIOLOGY 9 '•'•':• •.• " Figure 1. Crag nest site of Long-leggedBuzzards at Pekliuka (Sofia district). emergedshortly after. On this basis,the hatching the skin on the back of the largestnestling. Iris color interval at this nest was 29-44 hr. On 4 May the was dark brown and pupil colorwas dark grey-blue three young weighed96.1 g, 61.0 g, and 48.1 g and Rectrices,remiges, wing covertsand back feath- were aged four-plus d, three-plusd, and one-d old, ering were showing on 21 May, and on 25 May respectively.The fourth young, with shell still at- (22-26 d post-hatch)already formed dark bands tached,weighed 59.8 g. The iris colorof the nestlings (Fig. 3). However, feathershad barely sproutedin was blackish-brown,and the pupil color was sepia. the smallestnestling. Bills and talonswere black, and ceres,legs and feet The nestlingshad grown remarkably by 2 June yellow. The down was a dirty-white color with a (approximately 30-34-d-old) and were fully clad faint beige tint above. with feathers (Fig. 4). Iris color was a brownish On 11 May, one wk after the last younghatched, yellow-grey. Back, wings and underparts were col- only threeyoung were foundin the nest.The young- ored a chestnut brown. est nestling had disappeared.The remaining nest- When the nest was approachedon 18 June the lingswere now in seconddown, which wasmarkedly nestlingsbegan to disperse,walking and flapping denser and showed a slight ochre shading above. acrossthe rock face. On 21 June the nestlingshad Two years earlier, on 14 May 1981, I found three left the nest and were calling from the cliffs nearby nestlingsin the same plumage state in this nest. On as one adult circledoverhead. On 22 June only one 18 May 1983 the nestlingswere agedapproximately fledgling was seen near the nest (T. Michev, pers. 15-19-d-old. The down of the nestlingswas dense comm.).The fledglingremained at the nest-sitefor and coloreddirty greyish-whitewith an ochre tint. approximately 46-50 d and was flying at approxi- The tips of the first featherswere showingthrough mately 49-53 d. 10 ILIYA Ts. VATEV VOL. 21, NO. 1 Figure 2. Recently hatched chicks of the Long-legged Buzzard, and one "chipping" egg.Note Wea- sel as prey item in the nest. Behavior of Young. On 4 May 1983, the date Figure 4. Chicks of the Long-legged Buzzard at ap- the last nestlinghatched, the brood were extremely proximately 30-34-d-old in "defensive"pos- "tottery" and lay with their heads resting on the ture. nest. The nestlingsoften fell sidewayswhen at- tempting to move. The two larger nestlingsmade peckingmovements at each other'sbills, whilst fast the larger of the nestlingsto raise its head, call and movementof a human hand was required to induce open its bill. On 11 May the three nestlings(ap- proximately8-12-d-old) movedrestlessly about the nest, calling at intervals. The nestlingspanted with their bills ajar in the hot, middaysun, and the small- est nestlingtried to take shelter beneatha large leaf overhangingone cornerof the nest,as well as behind its largest sibling. The nestlingsmade no reaction to me reaching out to pick them up but glanced regularly skyward.The largestnestling was in "fro- zen" posture with its left foot on a small rodent (Microtussp.) which had beeneviscerated. Based on this evidence,the nestlingswere alreadyattempting to feed themselveson prey brought to the nest. On 18 May I foundthe nestlings(approximately 15-19-d-old) lying motionlessas if dead,a common. behavior in western North American buteos(C. M. Figure 3. Chicks of the Long-leggedBuzzard at ap- White, pers. comm.). Heads were pressedagainst proximately 22-26-d-old, lying "frozen" on the nest, and the nestlingswere utterly silent and the nest as if dead. remainedso even when I movedthem with my hand. SPRING 1987 LONG-LEGGED BUZZARD BREEDING BIOLOGY 11 Only the largestpecked at my hand. The nestlings prey, pendulum-like, in front of its incubatingmate remained still throughout my 15 rain stay at the beforefinally droppingthe prey onto the nest.The nest, althougheach movedtheir headsto follow the incubatingadult then rose, swallowedthe prey and overheadflights of Jackdaws(Corvus mortedula). flew away from the nest, and the relieving adult On 25 May the nestlings(approximately 22-26- settled to incubate. d-old) lay "frozen"on the nestand remainedsilent, One adult, presumably the female, was almost whereaseight d later on 2 June the nestlingsmoved constantlyin attendanceat the nest during the first quicklyto onecorner of the nestwhen I approached, week after hatch. Later, food was brought to the and assumeda defensiveposture. Wings were held nestlingsby both parents. During 10-hr watcheson out, and my hand was attackedwith bill and talons. 11 and 21 May 1983 at a distanceof approximately The two smaller nestlingslay on their backs,bills 800 m from the Pekliukanest, adults brought in food wide ajar, but attackedonly with their talons.Sim- 13 and 21 times, respectively.Prey was carried in ilar behaviorwas shownby two well-featherednest- the talons,rarely in the bill.

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