372 Short Communications [Auk, Vol. 99

JAMES,F. C. 1970. Geographicsize variation in MEUtqIER,K. 1951. Korrelation und umkonstruktion and its relationship to climate. Ecology 51: in dengr6ssbenbeziehungen Zwischen vogeltiff- 365-390. gel und vogelk6rper.Biol. Gen. 19: 403-443. LowE, P. R. 1934. On the evidence for the existence M/3LLE•HOFF,K. 1885. Die grosseder flugfluchen. of two speciesof steamerduck (Tachyeres),and Pflueger'sArch. Ges. Physiol.35: 407-453. primary and secondaryflightlessness in birds. MURPHY, g. C. 1936. Oceanic birds of South Amer- Ibis 4: 467495. ica, vol. 2. New York, Amer. Mus. Nat. Hist. MAGtqAtq,M. A. 1912. Modifications organiques PooLE,E. L. 1938. Weights and wing areasin North cons•ctives chez les oiseaux • l'absence de vol. American birds. Auk 55: 511-517. Bull. Mus. Hist. Nat. Paris 18: 524-530. RAIKOW, g. J. 1973. Locomotor mechanisms in --. 1913. Rapport de la surfacealaire avec le North American ducks. Wilson Bull. 85: 295-307. poids du corpschez les oiseaux.Bull. Mus. Hist. SAWLE,D. B. O. 1957. Adaptive in the Nat. Paris 19: 45-52. avian wing. Evolution 11: 212-224. --. 1922. Les caracteristiquesdes oiseaux sui- WELL,R, M. W. 1976. Ecology and behaviour of vant le mode de vol. Ann. Sci. Nat. (Ser. 10) 5: steamer ducks. Wildfowl 27: 45-53. 125-334. Received24 August1981, accepted 4 November1981. McNAI•, B. K. 1971. On the ecologicalsignificance of Bergmann'srule. Ecology52: 845-854.

Observationson migratoryTurkey and LesserYellow-headed Vultures in northern Colombia

FRIEDEMANN KOESTER1 Institutode Investigaciones Marinas "Punta de Betin," Santa Marta, Colombia,South America

TurkeyVultures ( aura) breed from south- somebirds of the flockhad conspicuousorange-yel- ern Canadato Tierra del Fuego,while LesserYellow- lowish heads and dirty-whitish wing patches that headed Vultures (Cathartes burrovianus) occur from identified them as Lesser Yellow-headed Vultures. M•xico through Central America to northern Argen- The resultspresented here are basedmainly on ob- tina and (Meyer de Schauensee1966). It has servationsand line-transect counts made along the long been known that Turkey Vultures breeding in coastbetween the ports of Barranquilla the northern parts of their rangeare migratory, and and SantaMarta in northern Colombia.They give a data are available on their arrival at or departure first accountof the magnitudeand ecologicalaspects from their breeding groundsin spring or fall (Bent of migrations in South America. 1937). Likewise, parts of their migration routesand Countsof vultureswere madeby driving alongthe winter ranges in Central America are well docu- Troncal del Caribe highway between Puente de la mented (Chapman1933, Wetmore 1965, Smith 1980). Barra, near the town of Cienaga, and Los Cocos,near Migrating TurkeyVultures were observedin north- the port of Barranquillaon the MagdalenaRiver. This western Colombiaby Dugand (1947),Haffer (1959), area includes most of Isla de Salamanca National and Olivares (1959), but there are no data on their Park. A detailed descriptionof this region, including abundanceor ecology. Becauseseasonal changes in a portrayalof its flora and fauna, is found in Franky their abundance in Panam• have been observed, it and Rodriguez (1976). Visibility along most of the is believed that the northern Lesser Yellow-headed highway was not impaired by vegetation, so nearly Vultures are also migratory (Ridgley 1976). all roosting or soaring vultures could be counted A tight flockof at least150 soaring Turkey Vultures within a broadcorridor of up to morethan 500m on was observed on 14 October 1978, some 16 km to the each side of the highway. Twenty-eight line tran- east of the town of Barranquilla, Colombia. Such an sects,each coveringa distanceof 44 kin, were made unusuallylarge number suggestedmigrating birds. between 1000 and 1500 from 17 October 1978 to 17 A closer view confirmed this; none of the vultures January1980. One persondrove, holding the speed showedthe whitish or dull yellow bandsacross the at a constant70 km, while a secondperson, using a backs of their necks that characterize the resident hand-operatedcounter, counted vultures with the race, Cathartesaura ruficollis.Although similar in nakedeye. Due to similaritiesin their plumagecol- generalappearance and size to the , oration and silhouettes,Turkey Vultures and Lesser Yellow-headed Vultures, when soaring or roosting, were difficult to separate at a distance. Separate Present address: Charles Darwin Research Station, CasiIla 58• 39, counts for resident Turkey Vultures and the race of Guayaquil, ,South America. migratingTurkey Vultureswere even more difficult. April 1982] ShortCommunications 373

TABLE 1. Date, relative abundance, and average number of vultures (C. aura and C. burrovianus) observed per line-transectcount from 17 October 1978 to 17 January 1980.

Number Num- 2 of indi- TotalJ ber of indi- Date viduals month counts viduals

17 Oct 1978 132 20 Oct 1978 137 353 3 117.7 23 Oct 1979 84 3 Nov 1978 210 4 Nov 1978 162 741 4 185.3 15 Nov 1978 117 26 Nov 1978 252 7 Dec 1978 154 14 Dec 1978 165 458 3 152.7 21 Dec 1978 139 8 Jan 1979 174' 17 Jan 1980 92 266 2 133.0 16 Feb 1979 47 Fig. 1. Yearly distribution of relative abundances 22 Feb 1979 100 147 2 73.5 16 Mar 1979 39 39 1 39.0 of Cathartesvultures in the study area, by months (J = January), from 28 line-transectcounts 17 Octo- 24 Apr 1979 27 27 1 27.0 4 May 1979 19 ber 1978 to 17 January 1980). Black areas indicate 15 May 1979 16 35 2 17.5 migration period. 3 Jun 1979 19 19 1 19.0 12 Jul 1979 24 20 Jul 1979 21 45 2 22.5 gration period, compared to a smaller proportion 2 Aug 1979 8 during the restof the year. Therefore,it appearslike- 5 Aug 1979 19 66 4 16.5 ly that migratory populationsof C. burrovianusalso 14 Aug 1979 24 wintered in the area. 20 Aug 1979 15 Blake (1977and pers. comm.) identifiesmigrating 4 Sep 1979 83 Turkey Vultures in Colombia, including the Santa 18 Sep 1979 72 223 3 74.3 26 Sep 1979 68 Marta region, as belonging to the race C. aura meri- dionalis.Indeed, basedon the known rangesof the races that could be possiblemigrants to the study area and on the measurementsof a female specimen collectedon 7 January1979, the Turkey Vultures re- The characteristicyellowish nape of resident birds ported here as wintering birds may well have be- was visible only at closerange and when birds were longed to this race rather than to C. aura septentrio- sitting or flying low. Becauseof theseuncertainties, nalis, as was assumed by Meyer de Schauensee line-transectcounts of residentand migrant Turkey (1964). The specimen,collected at PozosColorados, Vultures and Lesser Yellow-headed Vultures made Santa Marta, was cataloguedunder Nr. IND-A-3186 throughout the study were lumped into the single at the collectionof the Laboratoriode Investigacion categoryof Cathartesvultures. The only othervulture de Fauna Silvestre, Div. de Fauna Terrestre, INDER- of this genus, the Greater Yellow-head (C. melam- ENA, Bogota, D.E., Colombia. It measures as fol- brotus), is an Amazonian whose occurrence in lows: wing length (flattened),535 mm; tail length, the study area is highly unlikely. 270 mm; tarsus, 63.5 mm; culmen (from cere), 24.5 The abundance of vultures varied seasonally, in mm; body weight, 1,420 g; ovary small, in nonre- accordancewith the general migration pattem for productive state. The nominate race, C. aura aura, so nearctic migratory bird species (Table 1, Fig. 1). far reportedas a winter migrant only as far south as Thus, it is almostcertain that flocksof Turkey Vul- Panamfi,and C. aurajota, essentiallya highland bird tures observedalong the ColombianCaribbean coast not reported north of central Colombia, can both during the northernfall, winter, and spring seasons probably be ruled out as being involved in these were migrating or wintering birds. In addition, migrations(Blake pers. comm.). With respectto the Lesser Yellow-headed Vultures were observed in the Lesser Yellow-headed Vultures that were observed study area in greaternumbers during the migration to winter togetherwith the Turkey Vultures, it seems period, often mixed in with the flocksof Turkey Vul- reasonableto assign them to the nominate race C. tures. Roughly, 1 LesserYellow-headed Vulture to burrovianusburrovianus, which rangesfrom southern every 5-10 Turkey Vultures was seen during the mi- M6xico to Colombia. Previous records in northern 374 ShortCommunications [Auk, Vol. 99

TA•L• 2. Densities (individuals/km) of Cathartes vul- of only 30-50 m. During the first observationsin tures in the study area; 28 line-transect counts October 1978, the flocks of migrants roused in this along 44 km of coastline each for a total of 1,232 way had a rather spectaculareffect upon the local km; 2,419 vultures counted. BlackVultures (Coragypsatratus). Soon after the first TurkeyVultures had begunto soarabove their roost- Num- ing place,Black Vultures came in from all sides.The ber Number of of indi- speedof their flight and the way they flew in on a Period counts km viduals Density straight line to wheel about in the cloud of roused migrants suggestedthat they came to find . Migration 18 792 2,227 2.8 On suchan occasionon 17 October,several groups Nonmigration 10 440 192 0.4 of two and three King Vultures (Sarcoramphuspapa), Totals 28 1,232 2,419 (• = 1.6) almost never seen in this coastal area, were observed flying high above. Previousobservations of the be- havior of King, Black,and Turkey vulturesfeeding on carrion have shown (Koester and Koester-Stoew- esand 1978)that Turkey Vultures in northern Colom- SouthAmerica for the largerC. burrovianusurubutin- bia invariably are the first to appearat the carcass, ga include only April through October, suggesting attractingthrough their presenceBlack Vultures that migration from its southern range (Blake 1977). On in turn may lure King Vultures to the site. It seems 10 January1979 a specimensoaring with a flock of possible,therefore, that the latter two speciesmis- five wintering Turkey Vultureswas shotat the same interpreted the unusuallylarge flock of soaringmi- placewhere the Turkey Vulture describedabove had grantsas an indication of the presenceof food. previously been collected. It measured as follows: It seemsgenerally acceptedthat migrants in the wing length (flattened),495 mm; tail length, 255 mm; tropics harvest superabundantand/or sporadically tarsus,58.0 mm; culmen (from cere), 23.6 mm; body available resourcesand are usually subordinate to weight, 1,200 g; sex undetermined.Preservation of the residentspecies (Karr 1976). This may apply only this specimenwas not possible. in part at the subspecieslevel, when one considers If the data from the line transects are subdivided wintering versus resident Turkey Vultures. Al- into numbers of Cathartesvultures seen during the though no detailed data on this subjectwere gath- migration and nonmigration periods (according to ered, the amount of what appearedto be suitable the presenceor absenceof groupsof 10 or more Tur- food for the localTurkey Vultures did not seemto be key Vulturesthat soaredor roostedtogether without more abundant during the wintering period com- obvious presenceof food: black areasin Fig. 1), then pared to the rest of the year. Thus, if a relatively the relative abundance of vultures observedduring constantavailability of food permitted a relatively the migration period from Septemberto March (;?= stablepopulation of C. aura ruficollisto exist in the 123.7 individuals per transect count) was signifi- study area, the presenceof additional Turkey Vul- cantly higher than during the nonmigrationperiod tures, C. aura meridionalis,with presumablysimilar from April to August (• = 19.2 individuals per tran- feeding habits during the northern winter, should sect count):[ = 8.00• 2.86= t19; P • 0.01. The have resultedin a generalfood shortageand com- density of Cathartesvultures, expressedas the num- petition between these two races.Indeed, resident ber of individuals per kilometerof line transect,was Turkey Vultureswere never observedto sharea car- seven times higher (2.8 individuals/km) during the casswith their wintering conspecifics,which ap- migration period than during the nonmigrationpe- peared to be more powerful flyers and generally riod (0.4 individuals/km) (Table 2). strongerbirds. In a remarkablecontrast to the resi- Accordingto Smith (1980),migrating Turkey Vul- dents, migrants seemed to cope easily with the tures in Panam• tend to abstain from food. In this agressive feeding behavior of the Black Vultures. study, however,Turkey Vulturesthat had arrived in This was observedon 15 November1978, when eight great numbers were frequently observed feeding. migrants and two Black Vultures fed on the carcass Therefore,it may be inferred that they acceptedthis of a dog near the village of Tasajeras,Isla de Sala- area as their winter home and did not extend their manca. migration farther to the south. For severaldays after During the migrationperiod, residentTurkey Vul- their arrival, flocks of 100 and more individuals were tures were more numerous in certain locations in observed soaring and roosting jointly. Thereafter, which they had not been as frequentlyencountered these large flocks dissolvedinto smaller groups or during the rest of the year. At times, in Tayrona single individuals. Especially when roosting in NationalPark to the eastof SantaMarta, for example, groups, wintering vultures took flight readily at the the number of C. aura ruficollisnearly equaledthe approach of an observer even when he was still numbers of the common Black Vultures. It may be 100-200m away,while TurkeyVultures flushed dur- inferred from this that the wintering race displaced ing the nonmigrationperiod, i.e. residentbirds, usu- a certainpercentage of the residentrace to other hab- ally took flight when an observerwas at a distance itats. Bent (1937)wrote that Turkey Vultures are ef- April1982] ShortCommunications 375 fectivein cleaningstreets, garbage piles, and dump ticular interest. Becausevultures are large, conspic- heaps in cities and are often seen feeding on the uous birds whose feeding habits can be studied main highwaysin Floridawhere snakes, turtles, and without too muchdifficulty, studiesof their behavior small mammals have been killed by passing auto- and ecologycould contributesubstantially to our mobiles or where fish have been thrown away by presentknowledge of the ecologyof . fishermen.It is noteworthy that, in contrastto this I am indebted to my wife, Heide, for her constant statement,resident Turkey Vultures were virtually assistance with the transect counts. Dr. Emmet R. never seen feeding on garbageheaps and strictly Blake, Field Museum of Natural History, Chicago, avoided towns and cities where Black Vultures are and Dr. Michael K. Rylander, TexasTech. Univer- abundant.But, like Turkey Vulturesin Florida, C. sity, Lubbock, made valuable suggestionsand as- auraruficollis feeds on road kills and smallercarcasses sistedwith the Englishtext, respectively. alongthe highway in the study area. Comparedto residents,therefore, wintering Turkey Vultures ap- LITERATURE CITED pearedto exploita wider spectrumof food, as they Bœ•qT,A. C. 1937. Life histories of North American were observedfeeding on garbagenear Cienaga as well as on road kills. birds of prey. U.S. Natl. Mus. Bull. No. 167: 1-44. Seventimes as many Cathartesvultures existed in BLAKœ,E. R. 1977. Manual of neotropicalbirds. Chi- the studyarea during the migrationperiod as during cago,Univ. ChicagoPress. the restof the year (Table2). Perhapsthe exploitation CHAPMA•q,F. M. 1933. The migrationof Turkey Buz- of a wider rangeof food sources,comprising those zards as observed on Barro Colorado Island, Ca- fed upon by the local Turkey Vultures as well as nal Zone. Auk 50: 30-34. those used by the local BlackVultures, enableswin- DUGA•qD,A. 1947. Aves del Departamentodel At- teringTurkey Vultures to coexistwith both the res- lantico. Caldasia 4: 499•548. ident race and the Black Vultures successfully.No FRANKY,S. M., & P. I. RODRIGUEZ.1976. Parque such observationswere possiblein the case of the Nacional Isla de Salamanca. Bogota, INDER- LesserYellow-headed Vultures. Throughout the year ENA. they were seenmore frequently in the wetlandsand HAFFER,J. 1959. Notas sobre las aves de la region mangroveswamps south and north of the Troncal de Uraba Lozania 12: 1-49. del Caribehighway, where the majorityof the birds KARR,J. g. 1976. On the relative abundancesof mi- believed to be wintering were observed. grantsfrom the northtemperate zone in tropical The breedingseasons of the BlackVultures and habitats. Wilson Bull. 88: 433-458. Lesser Yellow-headed Vultures in the study area KOESTER,F., & H. KOESTER-STOEWESAIqD.1978. partly coincidewith the migration period of Turkey and Lesser Yellow-headed vultures from the north. Koenigsgeier--Beobachtungenim Tayrona-Na- While more detailed information on season and tionalparkim Norden Kolumbiens,Suedameri- ka. Zeitschr. Koelner Zoo, 21: 35-41. breeding biology of the BlackVulture in the area is --, & ---. In press.Zur Brutbiologiedes Ra- available (Koesterand Koester-Stoewesandin press), bengeiers,Coragyps atratus (Bechstein 1793), in our presentknowledge of the breedingseason of the Nordkolumbien, Suedamerika. Bonn. zool. LesserYellow-headed Vulture is limited to a single Beitr. observationof an adult accompaniedby two recently MEYERDE SCHAUENSEE,g. 1964. The birds of Co- fledged young on 11 May 1979 in the mangrove lombia. Narberth, Pennsylvania,Livingston. swampssouth of the CienagaGrande de SantaMar- --. 1966. The speciesof birds of SouthAmerica ta, known as the natural reserve area E1 Santuario. with their distribution. Acad. Nat. Sci. Phila- Nothing so far is known of the annualcycle of the delphia. residentTurkey Vulturesand how their cyclesmight OLiVAReS,A. 1959. Aves migratoriasen Colombia. comparewith those of the migrants. According to Rev. Acad. Col. Ciencias, vol. 10, No. 41: Smith (1980), however, Turkey Vultures in PanamPi 371-442. commenceegg laying in Februarythrough early RIDtrEY,R. S. 1976.A guideto the birdsof Panama. April. A similartiming of the breedingseason for C. Princeton,New Jersey,Princeton Univ. Press. auraruficollis in the studyarea is likely. Thus, during SMITH, N. G. 1980. and vulture migration in the northern winter, Turkey Vultures along the the neotropics,Pp. 51•55 in Migrant birds in the northerncoast of Colombiaare likely to be separated neotropics(A. Keast and E. S. Morton, Eds.). into breeding residentand nonbreedingwintering Washington,D.C., SmithsonianInst. Press. races. WœtMOR•,A. 1965. The birds of the Republic of A more extendedecological study of the relation Panama. Washington, D.C. SmithsonianMisc. of the migratoryvultures with the residentstreated Coil. No. 150. hereinand the resultinginter- and intraspecificcom- petition for food and its possibleeffects on the Received7 November1978, accepted7 October1981. breedingsuccess of the residentsshould be of par-