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J. Raptor Res. 24(1-2):19-25 ¸ 1990 The Raptor ResearchFoundation, Inc.

ROOST-TREE CHARACTERISTICS, FOOD HABITS AND SEASONAL ABUNDANCE OF ROOSTING EGYPTIAN IN NORTHERN SPAIN

OLGA CEBALLOS 1 Sociedadde CienciasAranzadi, Pl. I. Zuloaga (Museo), 20003 San Sebastian,Spain

Josv.A. DONAZAR EstacidnBioldgica de Doffaria,CSIC, Pabelldndel Perif, Avda. M • Luisa s.n., 41013 Sevilla,Spain

ABSTRACT.--SixEgyptian (Neophronpercnopterus) communal roosts were discoveredin northern Spain between1986-1988. The maximum number of EgyptianVultures observedvaried between8 and 138 (• = 55). Vultures generallyselected large, dead trees for roosting,and foragedprimarily on domestic mammalsand ,wild lagomorphsand garbage.In 1988 the largestroost was formedin late February and dissolvedin early September.Number of vulturespeaked in late July; 72.6% of the vulturesobserved were adults, 26.6% immatures and 0.8% juveniles. Immatures frequented roosts between May and September.Juveniles were observedin August and September.

Caracteristicasde los arbolesdormideros, habitos de alimentaci6ny abundanciaestacional de dormideros de buitres egipciosen el norte de Espafia

EXTRAGTO.--Seisdormideros comunales de buitresegipcios (Nephron percnopterus) han sidodescubiertos en el norte de Espafia, entre 1986-1988. E1 maximo nfimero de buitres egipciosobservados variaba entre 8 y 138 (• = 55). Los buitresgeneralmente seleccionaban grandes airboles muertos para dormideros,y se alimentabanprincipalmente de mamlferosy avesdom•sticos, liebres y basura.En 1988, el dormidero mas grandeha sido formadoa finesde febrero,y desocupadoa principiosde setiembre.E1 nfimero de buitres ha alcanzadosu maximo a fines de julio. 72.6% de los buitres observadoshan sido adultos, 26.6% han sidoaun inmaduros,y 0.8% en estadojuvenal. Los buitresinmaduros frecuentaban dormideros entre mayo y septiembre.Los buitres en estadojuvenil han sido observadosen agostoy septiembre. [Traducci0n de Eudoxio Paredes-Ruiz]

Egyptian Vultures (Neophronpercnopterus), like recent reports provide only anecdotalinformation, someother Old and New World vultures,congregate and detailedmonitoring of EgyptianVulture roost- in communal roosts. Roosts have been reported ing behavioris lacking. Here we describetree char- throughoutthe entire range of the species(Brown acteristics, food habits, and dynamics (seasonal and Amadon 1968, Cramp and Simmons 1980) changesin abundance)of spring-summerEgyptian though rarely occurringin the Western Palearctic. Vulture communalroosts in northern Spain. Cramp and Simmons(1980) pointedout roostsdur- STUDY AREA AND METHODS ing the 1800s in Istanbul and early 1900s in the The studywas carried out from 1986-1988 in a 13 000 southof Spain and the MacaronesianIslands. More km2 area coveringthe left bank of the upper valley of the recently,after declineof the speciesin , the Ebro River (northernSpain), includingparts of the prov- only reportedroosts are locatedon the Mediterra- incesof Navarra, Huesca and Zaragoza. Climate is influ- nean island of Menorca (Congost and Muntaner encedby the PyreneesMountain range which receives rain from the northwest.Unequal rainfall occursin the 1974), where up to 47 Egyptian Vultures have been Pyrenees(>2000 mm/yr) and in the Ebro valley (<400 countedroosting on cliffs and in pine trees.However, mm/yr). Vegetationin the Pyreneesis predominantlyfor- est [Scotspine (Pinussylvestrys), beech (Fagus sylvayica) and oak (Quercusspp.)] while in the Ebro valley herba- Presentaddress: Grupo de EstudiosBio16gicos UGAR- ceouspseudosteppe vegetation and cerealcultures predom- RA, C. Carlos III 19-4, 31002 Pamplona, Spain. inate.

19 20 Or,G^ CEB^t,t,OS AND Jose A. DONAZ^R VOL. 24, NOS. 1-2

Table 1. Gharacteristicsof EgyptianVulture roosts.The numberof checksand the information(number of Egyptian Vultures, date, % immatures)obtained from the checkswhen a large number of birds was seenis detailed. For other speciesseen regularly the maximum number observedis detailed.

ROOST

1 2 3 4 5 6

Substrate a Pines b Pines c White poplar Cliff Pinesa Number of checks 42 10 8 2 14 4 Max. no. Egypt.Vult. 138 43 52 72 14 8 Date 29 July 1988 29 July 1988 15 July 1987 6 July 1988 7 July 1987 7 July 1987 % immatures 27.5 18.6 19.6 28.3 5.1 25.0 Other species 210 -- -- 26 Black Kite 70 -- -- Red Kite 25 8 3 Raven 100 -- 60 a Pinushalepensis, b = p. sylvestris,c = p. nigra.

Roosttree characteristicswere studiedin 4 large roosts 4) Foliagecover (classified on a scaleof I to 5; a value of using comparisonswith control trees. Roost trees were I representeda tree with greenleaves on everybranch consideredto be those under which Egyptian Vulture and a value of 5 representeda defoliated (dead) tree), droppings,feathers and pellets could be found simulta- 5) Percentageof open spacearound the maximum di- neously. Control trees were chosenby random selection ameter of the crown of the tree. Glosedspace is taken in the roostarea. All treeswith a diameter at breastheight to be when the crownsof neighboringtrees were closer (DBH) >15 cm were includedin the analysis.The fol- than 2 m to that of the tree measured. lowing 5 variableswere evaluatedfor each roostand con- trol tree: Valuesfor roostand control trees were compared by Mann- Whitney U-tests(Siegel 1956). 1) Maximum DBH (cm); Food habits were studied in the 4 largest roostsby 2) Height (m) measuredwith opticalinstruments; analyzing pellets collected from beneath the roost trees 3) Number of trees (>15 cm DBH) in a 10 m radius; during September1988. Bones,hair and feathersobtained

Table 2. Gomparisonbetween the characteristicsof roost(r) and control (c) trees in each of 4 main roosts.In roost 1, the 3 nuclei(A, B, and G) havebeen considered separately. Mean, standarddeviation (parentheses) and significanceof the differencesfor eachvariable are shown(Mann-Whitney U-tests).

ROOSTS

1A lB 1C 2 3 4

R C R C R C R C R C R C N=5 N=5 N=6 N=6 N=5 N=5 N=9 N=12 N=6 N=8 N=13 N=7

1) Diameter (cm) 43.2 40.0 34.3 26.2 a 36.0 41.6 23.1 22.2 40.2 31.0 b 45.6 29.0 b (12.2) (9.0) (5.7) (3.3) (9.1) (12.1) (2.5) (2.5) (6.3) (5.7) (12.1) (9.6) 2) Height (m) 6.5 8.3 10.1 9.0 6.4 5.4 14.9 15.0 15.3 11.9 a 10.0 6.7 (2.2) (1.9) (1.4) (1.3) (1.1) (1.3) (0.3) (0.0) (1.8) (2.6) (2.4) (1.1) 3) Number of 0.6 1.6a 3.2 6.3 b 1.0 3.8 a 11.3 15.6 b 5.0 4.5 1.6 1.1 trees (0.6) (1.8) (1.5) (2.2) (0.7) (2.3) (2.2) (2.6) (2.4) (3.3) (1.0) (0.9) 4) Foliage(1-5) 5.0 1.8b 2.7 2.7 4.8 1.4 b 2.1 2.0 2.7 1.8 2.6 2.6 (0.0) (0.8) (0.8) (0.8) (0.5) (0.6) (0.3) (0.0) (0.8) (0.5) (1.0) (1.3) 5) Open space(%) 94.0 77.0 53.3 45.8 96.0 62.0 a 60.6 22.9 c 72.5 71.9 73.9 87.0 (13.4) (22.8) (12.1) (31.7) (8.9) (29.7) (12.1) (18.6) (14.8) (23.0) (21.4) (15.0) a p < 0.05; b p < 0.01; c p < 0.001. SPRING-SUMMER 1990 EGYPTIAN VULTURE ROOSTS 21 from pelletswere classifiedby comparisonwith collections Table 3. Resultsof pellet analysisof roostingEgyptian and occasionallyby consultingidentification keys (Faliu Vultures(values represent frequency of ap- et al. 1980, Pinto 1980). Most of the EgyptianVulture's pearanceper pellet). foodcomes from carrionwhich is difficultto quantify. For this reason,we decidedto estimateonly frequenciesof appearance/pellet(number of occurrencesx 100/total Roost numberof pellets)and not to calculatenumeric and bio- 1 2 3 4 massfrequencies. Seasonalchanges in numberof roostingEgyptian Vul- Mammals tures were studiedin the roostwhere the largestnumber Oryctolagus of birdswere present.We conductedcounts weekly from the end of February to the end of September1988. Counts cuniculus(wild) 42.4 16.7 4.1 19.1 were made at the end of the day by 2-3 observersworking Unidentified rodent -- 1.5 4.1 3.2 in such a way that the whole roost could be coveredsi- Eelis catus -- 1.5 6.1 -- multaneously.In other speciesof roostingvultures (Ca- Canisfamiliaris 1.7 -- 4.1 6.4 thartidae), countsare done on birds departing from the Meles meles -- 1.5 -- -- roostin the early morningdue to difficultyin conducting Vulpesvulpes 1.7 ------observationsin treeswith densefoliage (Sweeney and Fra- Equus caballus -- -- 2.0 -- ser 1986). Egyptian Vultures, however,roost in treeswith Susscrofa (domestic) 33.9 47.0 8.2 20.6 little foliage or, as often happens, in dead trees. Thus, Susscrofa (wild) -- 3.0 4.1 -- determiningnumbers in the eveningbefore darkness was Bos taurus 1.7 7.6 14.3 4.8 relativelyeasy. Three ageclasses (juvenile, immature and adult) were distinguishedby differencesin plumagecol- Ovisaries 20.3 50.0 73.5 22.2 oration(see Porter et al. 1974, Cramp and Simmons1980). Capra hircus -- 1.5 -- -- Telescopes(20-90 x) were usedin all observationsat dis- Unidentified mammal 8.5 1.5 2.0 1.6 tancesranging between 200 and 500 m. Birds Gallusgallus 54.2 25.8 10.2 95.2 RESULTS Corvus rnonedula -- -- 2.0 -- Description of Roostsand Tree Characteris- Unidentified Corvidae 1.7 4.6 -- 1.6 Unidentified birds 3.4 3.0 -- 6.4 tics. Six Egyptian Vulture communalroosts were located. General roost characteristics are described Reptiles ;n Table 1. Four roostswere in trees, 1 in Lacertalepida 1.7 ------Europeanwhite poplar (Populusalba), and 1 on a Fishes clay cliff. The maximumnumber of EgyptianVul- Unidentified fishes ------1.6 tures observedin each roost was highly variable Invertebrates (max = 138; min = 8). Percentageof birds in im- matureplumage was relatively similar between roosts Coleoptera 22.0 6.1 8.2 14.3 (19.6-28.3%). Griffon Vultures (Gypsfulvus),Red Garbage(synthetic Kites (Milvus rnilvus),Black Kites (M. migrans)and materials) 3.4 9.1 51.0 1.6 Common Ravens (Corvus corax) were observed Plant matter 47.5 48.5 24.5 27.0 roostingregularly with Egyptian Vultures. Occa- Number of pellets 59 66 49 63 sionally,individual birds of other specieswere also seenroosting [i.e., BootedEagle (Hieraab'tuspen- natus),Honey Buzzard(Pernis apivorus), Peregrine lB, 2, 3 and 4, homogeneityof the trees was no- Falcon (Falcoperegrinus) and Jackdaw (Corvusmo- ticeable, and differences between roost and control nedula)]. In all roostsEgyptian Vultures perched trees were necessarilysmall. In these roosts,birds togetherexcept in the caseof roost 1 which was chosetrees for roostingwith a large basal diameter. composedof 3 separatenuclei at an averagedistance Roost2 consistedof planted pine, and vultures roost- of 1210 m. EgyptianVultures roostedindiscrimi- ed in trees along the border of the forest.Vultures nately in the 3 nuclei.Changes seemed to depend strongly preferred isolated dead trees wherever on weather and human disturbance(DonSzar and available (roosts1A and 1C). Ceballos 1987). Food Habits. Foodof roostingEgyptian Vultures Differencesobserved among roosts with respectto was extremelyvaried (Table 3). A few specieswere tree-selection(Table 2) might simply be a result of representedin mostof the pellets: differentcharacteristics in a givenwoodlot. In roosts (Oryctolaguscuniculus), pig (Sus scrofadomestica), 22 OLGACEBALLOS AND Jose A. DON,•.ZAR VOL. 24, NOS. 1-2

. ß Total ß Immatures

140- ß Immatures

ß ß Juvemles

tß ßAdults 120:: -20 , MONTHS Figure 2. Monthly changes(number of vultures)in roost 1 during 1988ßChanges are differencesbe- tweenmonthly mean numbersof birds.

age, however,were not recruiteduntil April-May. BetweenMay and Septemberimmatures constituted , F. MARCH APRIL MAY JUNE JULY •UG. 5EP. a large part of the total number of birds (monthly average= 38.4%). Immigration rate of adults and Figure 1. Number of EgyptianVultures observed in roost immature birds differed noticeablythroughout the 1 during 1988. studyperiod (Fig. 2). Adults increasesharply from March-April and June-July, while immaturesin- sheep(Ovis aries) and Domestic Fowl (Gallusgallus). creasedmost sharply in the first 2 monthsof their Dominant prey remainsin pelletsvaried from one appearancein the roost(May-June). Consequently, roost to another and seemeda simple consequence the ratio of adultsto immaturesvaried substantially of availability of food.Thus, in roosts1 and 4, food during the year (Fig. 3). With the arrival of the first was basedon fowl raisedon nearby farms. In roost immatures, the number of adults per immature 1, wild rabbits, which were abundant in the area, droppednoticeably, gradually recovering later with also entered in the diet. In roost 2 a pig slaughter the arrival of new adults. Juvenile Egyptian Vul- house provided most of the food, and in roost 3, tures (hatchedin 1988) frequentedthe roost in the vultures foragedin a garbagedump containingre- lastweeks of Augustand the first weeksof September mains of slaughteredsheep. A high frequency of (Fig. 1). Juvenilesand immaturesleft the roost 2 plant matter in pelletscannot be accidental,given wk before adults. thatplant material dominated in mostpellets in which DISCUSSION •t appeared.Generally, plant remainsconsisted of Roost and Tree Characteristics.As in other parts stemsand seedsof wild and cultivatedgrains as well of the Palearctic(see Cramp and Simmons1980) as fruit seeds(cherry, melon and watermelon).The largestquantities of plant material appearedto be associatedwith hair and wool, suggestingthat vul- 20. turesingest plant matter to aid in pellet formation. Roost SeasonalDynamics. Resultsof weekly countsin roost 1 are summarizedin Figure 1. Vul- ,• 15' tures first arrived the last week of February. Num- _ bers increasedprogressively, reaching a maximum • lO in July-August,after which numbers dropped until the end of Septemberwhen the last birds left. Al- õ thoughoverall tendencies were constant,there were ß strongweekly fluctuations.A total of 1757 vultures were observedduring 1988; 1275 (72.6%) adults, 468 (26.6%) immatures and 14 (0.8%)juveniles. AP. MAY JUNE JUL. AUG. SEP. Throughoutthe studyperiod there were adult Egyp- Figure 3. Ratio of adults/immaturesin roost 1 during tian Vultures in the roost.Birds in immature plum- 1988. SPRING-SUMMER 1990 EGYPTIAN VULTURE ROOSTS 23 the Egyptian Vulture preferentiallychose trees for of plasticand syntheticmaterials might be explained roostingin our study area. The choiceof pines for for one of a variety of reasons:mistaken for bone roostingmay only be a consequenceof abundance fragments(Mundy 1982), as an aid to pellet for- •n the studyarea and of the fact that pinesin Spain mation, or ingestedaccidentally when vultures eat reach taller heights than broad-leafedtrees. Asso- food placedinside plasticbags (Ifiigo 1987). ciatedavian speciesobserved in roostswere mainly Roost Seasonal Dynamics. Progressiveincrease carrion-eaters,which supportsthe opinionthat mixed in the total numberof EgyptianVultures in the study roostsmay have a function related to transfer of area may only be a consequenceof greater avail- foraginginformation (Ward and Zahavi 1973, but ability of foodduring summer.In July, August and seeBayer 1982). However, speciesdid not scavenge Septemberthe itemsmost frequently consumed (hen, frequently togetherin the study area and usually pig and wild rabbit) undergo a higher death rate occupiedseparate zones in the roosts. than in winter and spring. Hen and pig mortality Observedtendencies in tree-selectionsuggest that is directly related to outdoor temperature (I.T.G. trees are chosen on the basis of 2 fundamental factors: Porcino,pers. comm.), and rabbit mortality increases 1) sizeof the tree (basaldiameter) which is necessary in the last part of the summerowing to myxomatosis for supportingseveral birds at a time; and 2) ability (pers. obs.). In consequence,the roostmight be fre- to enter and leave without the foliage of the roost quentedmore often at thesetimes by breedingand tree and neighboringtrees getting in the way (ten- non-breedingbirds searching for food,such as occurs dency to choosedead, isolatedtrees with an open in otherlarge roostingraptors (Isaacs and Anthony crown). Roosting New World vultures and large 1987). We believe, however, that this cannot be the eagleshave also been reportedto show a preference onlyvalid explanation, asthe availability of foodin for large treeswith easyaccess (Wright et al. 1986, our study area was extraordinarily high in all sea- Isaacs and Anthony 1987). Wright et al. (1986), sons.In the villagenearest roost 1, there were 26 000 however,indicated that wintering Black (Coragyps pigsand 51 000 henswhich were expectedto provide atratus)and Turkey Vultures( aura) choose a monthly averageof 15 and 153 carcasses,respec- treeswith abundantfoliage (conifers) which provide tively. On the other hand, immigration rate is high a favorable microclimate. This is not the case with during the months May-June before the expected the Egyptian Vulture, which tendsto choosetrees high mortality of livestock and wild rabbit takes without foliage probably becauseits roostsare in place. warm areas and form during warm seasons. In our opinion,the observeddynamics of the larg- Food Habits. RoostingEgyptian Vulture foodis, est roostcould be in responseto 2 factors:1) changes in general, similar to that of breedingpairs in the in reiative frequenciesin the popuiation of non- study area (see Donfizar and Ceballos1988) and breeding birds (adults and immatures); and 2) reflectsthe great foraging eclecticismof the species changesin the breedingstatus of adults. Spring mi- (Bergier and Cheylan 1980, Cramp and Simmons gration of adult Egyptian Vultures through Gi- 1980). In each roost, food habits seemto reflect ac- braltar continuesafter the start of the reproductive curatelythe availabilityof differentkinds of carrion seasonin Spain (see Cramp and Simmons 1980). in feeding groundsnearest to roosts.This was also For this reason,a progressiveincrease of adults in indicated by a radiotrackingstudy of 5 Egyptian the roostin early spring might result from numbers Vultures (2 adults; 1 immature) frequenting roosts of non-breedingbirds, perhaps adults in their first 1 and 3 (Donfizar and Ceballos 1987). The ap- plumage, migrating late. Moreover, the increasein pearanceof plant matter in pelletsis alsoknown in immaturesobserved in the roostin late springmay other species,such as Griffon Vultures also correspondto late migrants since in May and which ingestlarge portionsof carrion without hair June a great number of immatures can be seencross- or feathers(pers. obs.) and has also been reported ing from to Spain (Bergier 1987). On the in Cathartidae (Paterson 1984, Ifiigo 1987). The other hand, peaksobserved in the rate of increaseof appearanceof fruit seedsin pelletsalso suggests that adult vultures coincidewith critical periods in the vulturesmay exploitsome resources that canbe eas- breedingcycle: egg-laying (March-April) and the ily found in garbagedumps. Frequent consumption firstmonth of chickdevelopment (June-July). Roosts of tropical fruits has been reportedfor Black Vul- might receive a number of adults whose breeding turesin Mexico (Ifiigo 1987). Finally, the ingestion attempt had failed. However, this implies that roosts 24 OLG^ C•S^LLOS^•D Jos• A. Do•Az^I• VOL. 24, Nos. 1-2 would receive birds from a wide area since the num- ables), and a FPI-grant from the C.S.I.C. to one author ber of roostingadults makes up about 25% of the (J.A.D.), ProjectDGJCYT, PB87-0405. breedingpopulation of the studyarea, and frequency LITERATURE CITED of breedingfailure in the area is relativelylow (Do- BAYER,R.D. 1982. How important are coloniesas nfizar and Ceballos1988). Further, high numbers information centers. Auk 99:31-40. of immaturesobserved in the studiedroosts supports BERGIER,P. 1987. Les rapacesdiurnes du Maroc. An- our conclusion.The Egyptian Vulture, in common nales du C.E.E.P. no. 3. with otherlarge raptors(Brown and Amadon1968, -- AND G. CHEYLAN. 1980. Statut, succ•s de re- Hiraldo et al. 1979, Piper et al. 1981) may undergo productionet alimentationdu vautour percnopt•re a high pre-adult mortality, which leads us to con- Neophron percnopterusen France mediterranfienne. clude that immatures observed in our roosts come Alauda 48:75-97. from a wide area. This conclusionis reinforcedby BROWN,L. ANDD. AMADON. 1968. ,Hawks and the very scarcereports on observationsof immature Falcons of the world. Country Life Books, London. birdsout of roostsin Spain(J.L. Perea,pers. comm.). CEBALLOS,O. ANDJ.A. DONAZAR. 1989. Actividad,uso It has frequently been claimed that immatures do del espacioy cuidadoparental en una parejade Ah- moches(Neophron percnopterus) durante el periodode not return to Europe until acquiringadult plumage dependenciade los pollos.Ecologia 2:34-45. (Stresemann,Ridell in Cramp and Simmons1980, CONGOST,J. ANDJ. MUNTANER. 1974. Presenciaotofial Geroudet 1965). e invernaly concentraci6nde Neophronpercnopterus Resultsof a radiotelemetrystudy of 3 adult Egyp- en la isla de Menorca. Misc. Zool. 3:1-11. tian Vultures in the area of roosts1, 3 and 5 suggest CRAMP,S. ANDK.E.L. SIMMONS(EDS.). 1980. The birds that roostsreceive both breeding and non-breeding of the western Palearctic.Vol. 2. Oxford University adults (Donfizar and Ceballos 1987, Ceballos and Press, Oxford. Donfizar 1989). Two marked birds were non-breed- DONAZAR,J.A. AND O. CEBALLOS. 1987. Par•metros ing birds that dependedtotally on the roost and reproductoresy uso del espacioen el Alimoche(Neo- neighboring feeding sites. The other radio-tagged phronpercnopterus). Unpubl. report. I.C.O.N.A., Sec- ci6n de recursosnaturales renovables, Madrid. adult was a breedingfemale which only frequented -- AND • 1988. Alimentaci6ny tasas re- the roost at night. In roosts, productorasdel Alimoche(Neophron percnopterus) en the presenceof breedingadults from adjacentter- Navarra. Ardeola 35:3-13. ritoriesand of non-breedingadults has been reported FALIU, L., Y. LIGNEREUXAND J. BARRAT. 1980. Iden- (Rabenold 1986, 1987). Finally, the appearance tificationdes poils des mammiferes pyreneens. Dor•ana, during August and Septemberof juvenilesrecently Acta Vert. 7:125-212. fledged could be interpreted as the recruitment of GEROUDET,P. 1965. Les rapacesdiurnes et nocturnes family groups as happensin Black Vultures (Ra- d'Europe.Delachaux et Niestlfi, Neuchatel. benold1986). We did not, however,see any behavior HIRALDO,F., M. DELIBESAND J. CALDERON.1979. El in juveniles(begging, feedings by adults)which would QuebrantahuesosGypak•us barbatus (L.). I.C.O.N.A. Monograflas22, Madrid. indicatedependence. More probably,roosts are used II•IGO, E.E. 1987. Feedinghabits and ingestionof syn- as rest stopsby juveniles during migration. In fact, thetic productsin a populationfrom a young bird we marked rested 1 night in roost 6 Chiapas,New Mexico. ActaZool. Mex. (ns) 22:1-11. after starting migration. The bird's natal territory IsMcs, F.B. AND R.G. ANTHONY. 1987. Abundance, was 6 km from the roost, and the bird migrated foraging,and roostingof Bald Eagleswintering in the without its parents. Harney Basin, Oregon. Northw. Sci. 61:114-121. MUNDY, P.J. 1982. Comparativebiology of southern

ACKNOWLEDGMENTS Africanvultures. Vulture StudyGroup, Johannesburg. PATERSON,R.L., JR. 1984. High incidenceof plant ma- We are grateful to Alejandro Urmeneta and Ignacio terialand small mammals in theautumn diet of Turkey Garcia Bello for field assistance;to Fernando Hiraldo who Vulture in Virginia. WilsonBull. 96:467-469. providedguidance throughout this study and revisionof PINTO,M.V. 1980. Estudomorfo16gico dos pelosdos the manuscript;to SanfordR. Wilbur, David C. Houston, and Alistair Robertsonwho providedconstructive criti- mamiferosportugueses. Chaves para a sua determi- cismsof the manuscript; and to Catherine Miller who naqao.Actas I reuni6n Iberoamer. Zool. Vert.:629-680. made the English translation. The study was partially PIPER,S.E., P.J. MUNDY ANDJ.A. LEDGER. 1981. Es- financedby the Instituto Nacional para la Conservaci6n timatesof survival in the Gypscoproth- de la Naturaleza (Secci6nde RecursosNaturales Renov- eres.J. Anirn. Ecol. 50:815-825. SPRING-SUMMER 1990 EGYPTIAN VULTURE ROOSTS 25

PORTER,R.F., I. WILLIS, S. CHRISTENSENAND B.P. NIEL- dynamicsand monitoringtechniques in southwestVir- SEN. 1974. Flight identificationof Europeanraptors. ginia. Wildl. Soc.Bull. 14:49-54. T.& A.D. Poyser,Calton, England. WARD, P. AND A. ZAHAVI. 1973. The importance of RABENOLD,P.P. 1986. Roostattendance and aggression certain assemblagesof birds as "information-centres" in Black Vultures. Auk 104:647-653. for food-finding.Ibis 115:517-534. 1987. Recruitment for food in Black Vultures: WRIGHT, A.L., R.H. YAHNER AND G.L. STORM. 1986. evidencefor following from communal roosts.Anita. Roost-treecharacteristics and abundanceof wintering Behar. 35:1775-1785. vultures at a communal roost in south central Penn- SIEGEL,S. 1956. Non-parametric statisticsfor behavioral sylvania. Raptor Res. 20:102-107. sciences.McGraw-Hill Book Company, New York. SWEENEY,T.M. ANDJ.D. FRASER. 1986. Vulture roost Received20 March 1989; accepted15 December 1989