]. RaptorRes. 21(1):8-13 ¸ 1987 The Raptor ResearchFoundation, Inc. NOTES ON THE BREEDING BIOLOGY OF THE LONG-LEGGED (Buteorufinus) IN

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 of '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 . 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 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 (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 (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 (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. While nestlingswere lings on 13 June at the 1982 nest. still downy, the prey was fed piecemealto the brood On 4 June 1981 I watchedthe reactionof 28-d- by the adults. Prey larger than ( sp.) old nestlingsat the arrival of an adult with prey was fed by the adults even after the nestlingswere from a hide 25 m away. The nestlingsuttered soft well grown. cheepswhile the parent circledoverhead. The nest- People,chiefly herdsmen,entered the nestingter- lings grew quieter as the adult alightedbut reached ritory frequently. The displayedextraor- maximum intensity as the adult began feeding the dinary warinessin their approachto the nestwhen- young.Sometimes the adult left beforethe prey had ever human presencewas detected. The buzzards beencompletely eaten by the nestlings,at whichtime circledand glidedto and fro at relatively low altitude, the larger ones would attempt to feed themselves; often dropping to the ground. Only when the cause the nestlingsmanaged to do so competentlyat ap- of the disturbance had left the area would one of the proximatelyfour wk old. pair land at the nest, sometimesremaining on the Food. On sunnydays the main prey was Green nest rim for -<15 rain, totally still, before attending (Lacerta viridis) of different sizes.The fol- to the nestlings.If the adults noticed human ap- lowing prey items were found on the nest:(1 May proachearly in the seasonwhen transportingnest 1983) two Green Lizards and one Common material, or while carrying green boughsto lay on (Microtusarvalis); (4 May 1983) one Sibling Vole the nest besidethe nestlings,the material was im- (Microtus subarvalis),one (Mustela rtivalis) mediately dropped in flight and the adults left the and one Green ; (11 May 1983) one Common area. Adults in flight would attempt to drop food Vole and two Green Lizards. Lizards had fractured ontothe nestfrom a height of 2-4 m in responseto skulls or were beheaded, and the Weasel had frac- distantactivities of herdsmen.Incubating adults left tured neck vertebrae. the nestwhen I approachedin full view within 150- Behavior of Adults. Incubationbegan in early 200 m from the nest, but flushed when I came within April (on 9 April 1981 an adult was sitting on the 30-40 m to the nest from around the base of the nest) and endedin early May (see above)and was cliff. performedchiefly by what was presumedto be the Generally, the pair would circle 50-60 m above female, relievedby its mate for brief periodsonly, the cliff and call, but when I visited the nest between mostlyin the early afternoon.The non-incubating 1-4 May 1983 at the time of the hatch, the adults adult spentmuch of the day closeto the nest site flew about and called loudly and anxiously.When perchedeither on rockswhere it alsoroosted, or on I stoodone m from the nest,the adultsbegan diving the ground.During sunnyweather, mostlybetween at me with partly closedwings, making rushing 1500-1600H, the incubatingbird wouldrise from soundslike falling rocks.The diveswere madefrom the eggsand stand for a few minutes on the rim of a heightof 30-35 m and were repeatedseveral times, the nest. The adult would then turn the eggswith ending 8-10 m abovemy head. The "attack" of the its bill and settleon them onceagain. adults was most aggressiveon 11 May 1983, when Normally at nest-reliefthe incomingadult carried one adult, probably the male, was much the bolder prey, usuallya small rodent.Several times I watched and came within a few meters of me. One of the an interestingnest-relief ritual. The incomingadult adultsdove at me and droppeda Green Lizard "mis- held the prey by the tail in its bill and swungthe sile-fashion," which landed a few meters from me. 12 ILIYA Ts. VATEV VOL. 21, NO. 1

On later visitsthe pair wasless noisy and aggressive. oftendies through inability to competefor foodwith Usually their high circlingabove the nestwas short- its larger siblings(Mebs 1964). On my visitsto the lived, and the adults would disappearfrom view. Pekliuka nest both during and after hatching,un- One adult did show itself as I retreated from the eatenprey was presenton the nestrim, and watches area. from hidessuggested that adultshad little difficulty Vocalisations.Before and duringfeeding, downy in securingprey. Clearly, further researchis needed younguttered cheeps like youngdomestic fowl (Pek- here.Cramp and Simmons(1980) suggesta fledging liuka--4 June 1981). When nestswere visitedwhich periodfor Long-leggedBuzzards of "c. 40-42 days containedyoung, adults uttered calls resembling those or more," a figure markedlyexceeded by the ap- of the Common Buzzard ( buteo) but louder proximate49-53 d fledgingperiod recorded at Pek- and more shrill. liuka. Nest Adornment. After the hatch, I almost in- Michevet al. (1984) foundremains of eightprey variably foundsprays of greenerylying on the edge species(14 items) in pellets collectednear a Bul- of the nestcup. Though wilted and troddenby the garian nest of Long-leggedBuzzards. Two prey young, the sprayshad apparently been fresh when species,the Water Rat (Arvicolaterrestris) and the brought by the adults. I found flowering or leafy LesserMole Rat (Spalaxleucodon), were new to the boughs(-• 6.5 mm dia) of the following:apricot (Pru- spectrumof prey for the speciesas givenin Cramp nusarmeniaca) on 14 May 1981; commonpear andSimmons (1980). Nine preyitems of four species rus communis)and wild rose(Rosa sp.) on 4 May were found on the Pekliuka nest, of which the Wea- 1983; easternhornbeam (Carpinus orientalis) on 11 sel and Sibling Vole were new prey speciesto the May 1983;and willow (Salixsp.) on 18 and25 May buzzard'srecorded diet in Bulgaria.Numerous Green 1983. Lizards were carried to nestsin this study during sunny weather and in the study of Michev et al. DISCUSSION (1984). Recordedprey itemsvaried at bothsites, but Despite the smallnessof the study sample, the a preponderanceof speciesmade vulnerable by bask- relativedearth of publishedinformation on the Long- ing habits was shown. European Susliks (Citellus leggedBuzzard's breeding cycle justifies comparison citellus)figured importantlyin the diet of Long- of my findingswith data in print. Nests in Bulgaria leggedBuzzards at another Bulgarian site (Michev are almostinvariably on cliffs. Most of the 14 nests et al. 1984). reported by Michev et al. (1984) and all the nests Cramp and Simmons(1980) did not reporton the reportedin this studywere within 500 m of moving role of the sexesduring incubation.The brief in- or standing water. Numbers and variety of small cubationduty undertakenby what waspresumed to and medium-sizedprey may thus be greater in the be the male at the Pekliuka nest site reflects the vicinityof water. Diameterof bothnests in thisstudy patterngiven for the CommonBuzzard (Cramp and is somewhatsmaller than the averagevalue (70 m) Simmons1980). The nest-relief ritual observeddur- reported by Dementiev and Gladkov (1954) for the ing my study has not been reported for either the Soviet Union. Long-leggedBuzzard or the Common Buzzard. Dimensionsof two eggsmeasured in this study, ACKNOWLEDGMENTS and the values of 60.3-63.1 mm x 45.4-50.0 mm I am indebted to Krasimir Mihailov for his assistance for eight eggsreported by Michev et al. (1984), are on visitsto somenests; to the late Nikolai Boevand Tanyu within the range reportedby Cramp and Simmons Michev of the Bulgarian Academy of Sciencesfor con- (1980) but are closestto the mean for 10 eggsfrom structivecriticism of the manuscript;to John Lawton Rob- erts who assistedwith the manuscriptand translationinto recordedby Makatsch (1974). The indica- English;to SlavchoGerasimov of the ZoologicalInstitute tion here is that egg dimension is uniform within (of B.A.N., Sofia)for identificationof vertebrateprey spec- the Balkanpopulation of Long-leggedBuzzards. The imens;and to Dimitar Radkovof the Instituteof Forestry mostcommon clutch size in this studywas four eggs, (of B.A.N., Sofia) for identifyingplant specimensfrom nestsof the Long-leggedBuzzard. which agreeswith the findings of Dementiev and Gladkov (1954) and Michev et al. (1984). LITERATURE CITED Only three of the four eggsat each of the two BROWN,L. AND D. AMADON. 1968. , hawks and nestsobserved in this studygave rise to flying young. falconsof the world. Vol. 2, GountryLife Books,Lon- The last young to hatch of the Common Buzzard don. SPRING 1987 LONG-LEGGED BUZZARD BREEDING BIOLOGY 13

CRAMP, S. AND K. E. L. SIMMONS(EDS.). 1980. The MEBS,T. 1964. Zur Biologieund Populationsdynamik birds of the western Palearctic. Vol. 2, Oxford Uni- des Mausebussards(Buteo buteo).J. fur Ornith. 105: versityPress, Oxford. 247-306. DEMENTIEV, G. P. AND N. A. GLADKOV. 1954. Birds of MICHEV, r. 1986. The red bookof Bulgaria. Academy the SovietUnion. Vol. 1, StatePublishing House, Mos- of Sciences,Sofia. (In Bulgarian) cow. (In Russian) --, I. VATEV, P. SIMEONOVAND C. PROFIROV. 1984. GLUTZ VON BLOTZHEIM, U. N., K. M. BAUER AND E. Distribution and nestingof the Long-leggedBuzzard BEZZEL. 1971. Handbuch der V/3gel Mitteleuropas. (Buteo rufinus) in Bulgaria. Ekologia 13:74-82. (In Vol. 4, AkademischeVerlagsgesellschaft, Frankfurt am Bulgarian) Main. HARRISON,C. 1975. A field guideto the nests,eggs and Department of General Biology, MedicoblologicalIn- nestlingsof Europeanbirds with North and the stitute,Medical Academy,1'}31 Sofia, BULGARIA. . Collins, London. HUDSON,I. 1975. Threatened birds of Europe. Mac- Received30 May 1985; Accepted5 January 1987 millan, London. MAKATSCH,W. 1974. Die Eier Der V/3gel Europas. Vol. 1, Neumann Verlag, Leipzig-Radebeul.

Western Raptor Management Symposiumand Workshop. The Western Raptor ManagementSymposium and Workshop,co-organized by the National Wildlife Federationand the Idaho Chapter of The Wildlife Society,will be held 26-28 October1987 in Boise,Idaho. The symposiumwill featuretechnical paper sessionson the statusof western raptorsand their habitats,land use activitiesimpacting raptors, as well as workshopsand a postersession. For more information, contact the National Wildlife Federation, Institute for Wildlife Research, Department 162, 1412 Sixteenth Street Northwest, Washington, DC 20036-2266, or telephone (703) 790-4264.