j Raptor Res. 28(1):39-42 ¸ 1994 The Raptor ResearchFoundation, Inc.

DIET, BREEDING SUCCESS, AND NEST-SITE SELECTION OF THE SHORT-TOED EAGLE (Circaetusgallicus) IN NORTHEASTERN GREECE

CHRISTOS G. VLACHOS AND NIKOLAOS K. PAPAGEORGIOU Departmentof Forestryand Natural Environment,Laboratory of Wildlifeand FreshwaterFisheries, Universityof Thessaloniki,54006 Thessaloniki,Greece

ABsTR^CT.--Forty-eightpellets of short-toedeagles (Circaetus gallicus) collected during 1988-90 in north- easternGreece were examinedto determinethe eagle'sfood habits.The main prey were reptiles (87.2% by frequencyof occurrence)followed by birds(6.9%) and rodents(5.9%). The mostcommon prey species were Montpellier snake(Malpopolon monspessulanus, 29.4%), grasssnake (Natfix natfix, 20.6%), lizards (Lacertaspp., 18.7%),and Europeanglass lizard (Ophisaurusapodus, 11.8%). Short-toed eagles preferred to nestin old pines (Pinusbrutia, 80% and P. nigra, 20%). Nest treeshad a mean height of 12.7 q- 2.9 m, d.b.h. of 43.5 +_ 10.9 cm, and age of 85 +_21.4 yr. The averagedistance between neighboring active nestswas 2200 m (range640-3250 m). Short-toedeagles' mean breeding success was 0.86 fledgedyoung/ nest. KEY WORDS: breeding;Circaetus gallicus; food habits; Greece; short-toed eagle.

Dieta, gxitoreproductivo y selecci6nde sitiosde nidificaci6nde Circaetusgallicus en el norestede Grecia RESUMEN.--Atravgs de cuarentay ochoegagr0pilas, colectadas entre 1988y 1990 en el norestede Grecia, sedeterminaron los hflbitos alimentarios de Circaetusgallicus. Los reptilesconstituyeron la presaprincipal (87.2%), sequidosde las aves(6.9%) y de roedores(5.9%). Las presasmfls comunes fueron las serpientes Malpopolonmonspessulanus (29.4%) y Natfix natfix (20.6%), loslagartos Lacerta spp. (18.7%) y Ophisaurus apodus(11.8%). C. gallicus,prefiri0 nidificar en Pinus brutia (80%) y P. nigra (20%). Los nidos se encontraban a una altura media de 12.7 m (DS = 2.9 m), en firboles con un difmetro a la altura del pechode 43.5 cm (DS = 10.9 cm) y de una edad de 85 aftos(DS = 21.4 aftos).La distanciapromedio entre nidosvecinos activos fug de 2200 m (rango 640-3250 m). La media del gxito reproductivofug de 0.86 juveniles volantonespor nido. [Traducci6n de Ivan Lazo]

Short-toedeagle (Circaetusgallicus) food habits serve since 1980 due to its unique raptor fauna. A and nesting habitat characteristicshave been re- total of 20 birdsof prey breedin the reserveincluding portedby Brown and Amadon(1968), Ali and Rip- cinereousvulture (Aegypiusmonachus), griffon vul- ley (1968), Glutz von Blotzheimet al. (1971), and ture (Gypsfulvus), imperial eagle (Aquila heliaca), Massimo (1989). However, such data are not avail- golden eagle (A. chrysaetos)and white-tailed eagle able for Greece. (Haliaeetusalbicilla), making the area not only of The objectivesof our studywere to examinethe: national but also of international importance. (1) diet, (2) nest site selection,and (3) breeding The reserve covers an area of about 7000 ha and successof short-toedeagle in northeasternGreece. it is part of a large forest complexof about 40 000 STUD'/ ARE^ ha. Vegetationincludes Pinus brutia,P. nigra, Quer- The study was conductedfrom March 1988 to cusconferta, and Q. cerris.Other speciesoccurring September 1990 in Dadia Forest, northeastern with lower frequency are Erica arborea, Phillyrea Greece, which is consideredone of the most impor- media, Arbutusandrachne, and Juniperusoxycedrus tant breedingareas of short-toedeagles in the coun- The climate is mediterraneanwith dry summers try (Hallman unpubl.data). Dadia Forestis located and rainy winters. During March to September between 40ø59'-41ø15'N and 2ø19'-2ø36'E. It lies (breeding season for short-toed eagle) the mean from 50-800 m above sea level. monthly temperaturewas 19.4øCwith minima and The study area has been declareda wildlife re- maxima of 8.9øC (March) and 27.6øC (July), re-

39 40 CHRISTOSG. VLACHOSAND NIKOL^OS K. PAPAGEORGIOU VOL. 28, NO. 1

Table 1. Compositionof pellets(N = 48) foundin short- 1989). The abundanceof reptiles was estimated using toed eagle nestsin northeasternGreece. transectsin different biotopes.In total 18 transects(100 x 5 m each) were used and were counted at 1000 H and 1700 H. NUMBER FREQUENCY The height, age, and diameterbreast height (DBH) of OF INDI- OF OCCUR- the nest tree, and the height of the nest, the diameter of VIDUALS RENCE the branch where the nestwas placed,and the distanceof SPECIES N % the nest from the trunk were recorded for each nest tree The nestinghabitat wasdetermined by vegetationanalysis Reptiles within a plot 50 x 20 m centeredon the nest. Malpopolonmonspessulanus 30 29.4 Natfix natfix 21 20.6 RESULTS Natfix tessdata 4 3.9 Diet. A total of 48 pelletswere collectedduring Elaphe situla 2 1.9 Vipera amodytes 1 0.9 the 3-yr study period. The resultsof the analysis Ophisaurusapodus 12 11.8 are presentedin Table 1. The data showthat short- Lacerta sp. 19 18.7 toed eagles'main food group by frequencyof oc- Birds 7 6.9 currencewas reptiles (87.2%) followed by birds

Mammals (6.9%), and rodents(5.9%). Reptile densityvaried considerablyamong the biotopes(Table 2). The main Apodemussylvaticus 6 5.9 period of reptile abundancein our studyarea starts Total 102 100.0 from the beginningof April to the end of September. spectively.The mean monthly precipitationduring the above period was 40.6 mm with minima and Nesting Sites. Eighty percentof the short-toed maxima of 0.0 mm (August) and 52.4 mm (June), eagle nestsfound in the study area were in Pinus respectively. brutia and 20% in Pinus nigra. Nest tree height was

METHODS much lessvariable than age and DBH. Short-toed eaglespreferred old pineswith mean height of 12.7 The diet of the short-toedeagle was determinedby analysisof pellets found in the nests.Active nestswere + 2.9 m, DBH of 43.5 + 10.9 cm and 85 + 21.4 locatedat the beginningof the breedingseason and were yr of age. Nests were locatedon brancheswith a visitedat irregular intervalsto collectregurgitated pellets. mean diameter of 13.5 + 3.3 cm and a mean distance Most pelletswere collectedafter the hatchingof the chicks from the trunk of 1.4 + 0.3 m. to avoid disturbance at the nests. The identificationof reptile prey wasaccomplished with Vegetationanalysis around each nest tree revealed a scalekey (Papageorgiouet al. 1993). Mammals were that nest-sitehabitats selected by short-toedeagles identified using a hair key (Papageorgiouand Sfougaris were foreststands with open canopy(40-60%) and

Table 2. Density of reptiles in different biotopesin Dadia Forest (individuals/ha).

NONINTEN- SHRUBLAND

SIVELY WITHIN CULTIVATED CULTIVATED DENSE PINE OPEN PINE DEGRADED SPECIES LAND LAND RANGELAND FOREST FOREST OAK FOREST

Malpopolonrnompes•ulanus 1 3 2 1 2 1 Ophisaurusapodus 1 3 1 -- 3 2 Natfix natfix 6 3 1 -- -- 2 Vzperaamodyte• -- -- 1 -- 1 1 Colubernaiadurn -- 1 ------1 Lacerta viridis 4 13 10 -- 4 14 Lacerta trihneata 2 9 4 -- 2 8 Lacertapraticola -- 5 2 -- -- 6 Podarcis taurica ..... 3 Total 14 37 21 1 12 38 MARCH 1994 SHORT-TOED EAGLE BIOLOGY 41

' ß ..... Rainfall -' Temperature 120

225 110

100 2OO

•' 90 .•, 175 &

150 '• E 70

125 E õ 60 E

IO0

I F M A M J J A S O N D Wet..... Higherapp...... freptiles •.• D•y...... •1 Wet...... Figure 1. Annual breedingcycle of short-toedeagle in Dadia Forest. with the nesttree being the dominantone. The nest- neuver through closedstands and the potential of ing siteswere locatedat an elevationranging from openhabitat to supporta high densityof reptiles. 50-600 m. The average nearest distancebetween The high populationdensity of the short-toedea- neighboringactive nestswas 2.2 _-!-0.48 km. gle in the Dadia Forest (1 pair/1370 ha) and the Breeding.The breedingcycle of short-toedeagles observedhigh breeding successindicates that the is given in Fig. 1. The eaglesarrived on the study Dadia Forest'spotential for food productionand areaat the endof March and the layingperiod began nestingsites is adequateto meet the short-toedea- between10-20 of April. The hatchingdate, after an gle'srequirements. This conclusionagrees with Hel- averageincubation period of 47 d, was estimatedto mer and Scolte(unpubl. data) who reportedthat the be the beginningof June. The breedingpairs, clutch northeasternpart of Greece supportsthe highest sizeand breedingsuccess of short-toedeagles is pre- reptiledensity in Europe.The main periodof reptile sentedin Table 3. All youngthat hatchedwere reared abundance in Dadia Forest coincides with the breed- successfully.

DISCUSSION Our resultson the diet of short-toedeagle agree Table 3. Breedingsuccess of the short-toedeagle in northeastern Greece. with previousresearch elsewhere (Boudoint et al. 1953, Brown and Amadon 1968, Glutz von Blotz- heimet al. 1971). The staplediet of short-toedeagles NUMBER NUMBER NUMBER OF NUMBER OF HATCH- OF FLEDG- consistsof reptiles, occasionallysupplemented with birds and rodents. BREEDING OF LINGS/ LINGS/ YEAR PAIRS EGGS/NEST NEST NEST Short-toedeagles prefer breedingareas with dry and warm climate and open discontinuousforest 1988 10 1 0.8 0.8 standsand open habitat. The selectionof suchhab- 1989 12 1 0.92 0.92 1990 11 1 0.91 0.91 itat reflectsthe short-toedeagle's inability to ma- 42 CHRISTOS G. VLACHOS AND NIKOLAOS K. P^P^GEORG•OU VOL. 28, NO. 1

ing cycleof short-toedeagles, therefore contributing Vol. 4. AcademischeVerlagsgesselschaft, Frankfurt am to successfulrearing of young. Main, Germany. MASSIMO,B. 1989. Status del Biancone(Circaetus gal- LITERATURE CITED licus) dell' Aquila reale (Aquila chrysaetus)-edel Pel- ALl, S. AND S.D. RIPLE¾. 1968. Handbook of the birds legrino (Falcoperegrinus) in valle d' Aosta.Boll. Mus of India and Pakistan. Oxford Univ. Press, London, Reg. Sci. Nat. Torino. Vol. 7 No. 1. U.K. PAPAGEORGIOU,N. AND A. SFOUGARIS. 1989. Identifi- BOUDOINT, Y., A. BROSSET,L. BUREAU, G. GUICHARD cation of mammals by hair morphology.Univ. Press, AND N. MAYAUD. 1953. Etude de la biologie du Thessaloniki, Greece. CircaeteJean le Blanc. Alauda21:86-112. --, C. VLACHOSAND D. BACALOUDIS.1993. Iden- Br,owN, L.H. AND D. AMADON. 1968. Eagles, hawks tificationof reptilesby scalemorphology. Univ. Press, and falconsof the world. Country Life Books,London, Thessaloniki, Greece. U.K. GLUTZ VON BLOTZHEIM, U.N., K.M. BAURERAND E. BEzzm.. 1971. Handbuch der Vogel Mitteleuropas, Received12 July 1993; accepted2 December1993