Turkey Vulture Surveys in Cuba

J. RaptorRes. 22(1):3-7 ¸ 1988 The Raptor ResearchFoundation, Inc.

TURKEY VULTURE SURVEYS IN CUBA

CARLOSWOTZKOW AND JAMESW. WILEY

ABSTRACT.--TurkeyVultures (Cathartesaura), were surveyedmonthly in Cuba from March 1982- January 1983. A total of 25 371 vultureswere tallied in 7186 km (3.5 vultures/transectkm) of roadside countingalong main highwaysleading from the city of La Habana (northwesternCuba) to the city of Las Tunas (southeast).Numbers of vulturescounted declined substantially beyond 200 m from the_ transectroad. Density of vulturesobserved within 200 m of the roadalong the transectroute was 0.06/ ha. Highestcounts were obtained in March,April andJune. Turkey Vulture flying activity was greatest during the periods0900-1200 H and 1400-1700 H.

In recentyears Turkey Vulture (Cathartesaura) (Havana) on the northwestern coast268 km to the south- numbers have declined in parts of North America eastthrough the interior to Santa Clara (Villa Clara Prov- (Brown 1976; Wilbur 1983; Alvarez del Toro and ince) and continued402.5 km to the southeastthrough the interior alongthe CarreteraCentral ("Central Highway") Phillips in Wilbur 1983). Ellis et al. (1983) reported from SantaClara to Victoria delas Tunas (Fig. 1). Surveys Turkey Vultures commonover most of Latin Amer- were discontinuedwhile passingthrough towns and cities, ica in 1978 and 1979, and Webster (1975, 1978) thus countswere made along 654 km of the route (Table suggestedthat numbers of wintering Turkey Vul- 1; the June 1982 count was reducedto 652 km due to rain). One observer(CW) conductedeach survey. tureshave increased in the lower Rio Grande valley Most of the transectroute passedthrough fiat, cultivated of Texas. Wilbur (1983) characterizedthe Turkey lands or rolling hills of <200 m elevation,interspersed Vulture as an abundant species,but one that should with remnant savannasof royal palm (Roystonearegia) be carefully monitored. Aside from the studiesof and silk-cotton-tree(Ceiba pentandra) or royal palm and Santana et al. (1986a, 1986b), little is known of saman(Pithecellobium saman) and dry brush-and wood- lands. View was largely unobstructed,although a small Turkey Vultures in the West Indies. Populationsin sectionhas low secondarybrush. However, the Carretera Puerto Rico and Hispaniola may have been intro- Central passesthrough somewoods and hills which re- ducedfrom Cuba (Wetmore 1916; Garrido and Gar- duced detection distances. cia Montafia 1975; Dod 1978), althoughSantana et Annual averagetemp along the surveyroute fluctuates between 23øC and 26øC, with extremes of IøC and 38øC al. (1986a) argue that vulturesarrived in the south- (Instituto Cubano de Geodesiay Cartografla 1978). Av- ern Greater Antilles by natural range expansion eragesummer temp ranges from 25ø-28øCwith July and once forests were cleared and livestock was intro- Augustbeing the warmestmonths. Average winter temp ducedby Europeancolonists in the 1800s.The species rangesfrom 21ø-24øCwith the lowesttemp in February. is commonin all regionsof Cuba, as well as on the Annual rainfall averages1000-1600 mm. May through Octoberis the period of greatestrainfall (average800- Isle of Pines (Isle of Youth) and coastalcays (Gar- 1200 mm); November through April is the dry season rido and Garcia Montafia 1975). (200-400 mm). Our objectiveswere: 1) to collectvulture popu- Surveyswere conductedusing public transportation(bus, lation data along establishedroutes to serve as a car or truck) at an averagespeed of 72.7 km/hr alongthe route.Surveys took approximately nine hr to completeand baselinefor comparisonwith future surveysand in most surveyswere conductedon two different days, re- determininglong-term trends in vulture populations suitingin the secondpart of the surveybeing an average in Cuba; 2) to conducta preliminary study of sea- of three d (range one-nine) after the first (Table 1). Sur- sonaltrends in vulture detectability;and 3) to de- veys were completedin one d in August and November 1982 and in January 1983. Vultureswere countedon both termine activity patternsof vultures in Cuba. sides of the road and numbers tabulated in one of 14 horizontaldistance (m) categoriesfrom the roadas follows 0-25, 26-50, 51-100, 101-150, 151-200, 201-250, 251- STUDY AREA AND METHODS 300, 301-350, 351-400, 401-450, 451-500, 501-550, 551- We used a "road count" method (reviewed in Fuller 600, and >600 m. However, theseincrements proved to and Mosher 1981, 1987; seealso Ellis et al. 1983; Hubbard be too narrow for the level of observeraccuracy attained 1983; Andersenet al. 1985) to conduct11 surveysalong duringthe surveys.We later modifieddistance categories a 670.5 km transectroute (public highways)at monthly (and combinedearlier observations)as follows: 0-100, intervalsbeginning in March 1982 and endingin January 101-200, 201-400, 401-600, and >600 m. 1983 (Table 1). The route extended from La Habana Activity and time of day were noted for each vulture 4 CARLOSWOTZKOW AND JAMES W. WILEY VOL. 22, No. 1

8'40 ' 8•o ' sbo ' iso ?'co ' LaHabana•c---•,,...,(.,.., •

•,F..Camagu©y I,leofPine, %'•;;•:•lc•Carretera Central

CARIBBEAN SEA CUB

Figure 1. Turkey Vulture surveyroute along the "New Highway"and CarreteraCentral in Cuba,and major geographicfeatures along route. sighted.Flying activity was weighted accordingto sam- Individual transectswere divided into sevenequal seg- pling effort becauseall periodswere not sampledequally. ments (93 km each) to estimate variancesof vultures ob- Generalweather conditions (clear, partly cloudy,complete servedwithin surveysand to allow statisticalcomparisons cloud cover, rain; wind conditions) were recorded. Counts among the surveys.Also, numbers of vultures observed were not made during periodsof poor visibility. were comparedamong six regions(range 50-100 km in

Table 1. Summaryof Turkey Vulture transectconditions and chronology,La Habana to Victoria de las Tunas, Cuba, March 1982-January 1983.

TRANSECT

DIS- SURVEY MEAN WEATH- SURVEY START FINISH TANCE TIME SPEED ER No. DATE TOWN TIMEa TOWN TIMEa (KM) (HR) (KM/HR) INDEXb 1 22 Mar La Habana 0815 Camagfiey 1755 536 7.5 72.0 4.5 25 Mar Las Tunas 0730 Camagfiey 1250 114 1.8 64.0 5.0 2 8 Apr La Habana 0730 Sibanicfi 1735 582 7.8 74.6 2.0 12 Apr Las Tunas 1010 Sibanic6 1155 72 1.2 72.7 2.0 3 26 May Santa Clara 0905 Las Tunas 1600 384 5.2 73.9 4.0 29 May Santa Clara 1230 La Habana 1640 268 4.2 64.3 4.0 4 12 Jun La Habana 1315 Santa Clara 1640 268 4.3 63.1 4.0 16 Jun Las Tunas 1000 Santa Clara 1702 384 4.9 78.9 5.0 5 5 Jul La Habana 0745 Gufiimaro 1805 612 8.3 73.4 5.0 7 Jul Las Tunas 1020 Gu•timaro 1101 42 0.7 60.0 3.0 6 13 Aug La Habana 0600 Las Tunas 1718 656 9.5 69.0 4.0 7 20 Sep Las Tunas 1020 Santa Clara 1710 384 4.9 78.4 4.0 29 Sep Santa Clara 0830 La Habana 1215 268 3.8 75.6 5.0 8 8 Oct La Habana 0900 Sibanicfi 1810 582 7.1 82.0 3.0 11 Oct Las Tunas 0800 Sibanicfi 0907 72 0.9 77.4 4.5 9 29 Nov Las Tunas 0900 La Habana 1845 654 8.4 77.9 3.0 10 20 Dec La Habana 0900 Camagiiey 1758 540 6.9 78.8 3.5 24 Dec Las Tunas 0952 Camagfiey 1133 114 1.4 80.3 3.0 11 8 Jan La Habana 0615 Las Tunas 1702 654 9.4 69.6 1.0

Eastern time zone. Weatherindex: 5 = clear,4 = mostlyclear, 3 = mostlycloudy, 2 = completecloud cover, 1 = completecloud coverwith occasional raiD. SPRING 1988 TURKEY VULTURES IN CUBA 5

length) which reflecteddifferences in habitat along the Table 2. Results of surveysfor Turkey Vultures, La survey route. Habana to Victoria de las Tunas, Cuba, March Parametric analyseswere used unlessdata were non- 1982-January 1983. normal; in thosecases, nonparametric tests were applied. Chi-square goodnessof fit tests (Zar 1974:80-81) were used to determinenormality. Analysis of variance (AN- NUMBER OVA) and Spearmanrank correlationcoefficients (rs) fol- low Zar (1974). Significancelevel was set at 0.05. SURVEY VULTURES VULTURES/ NO. MONTH SIGHTED KM

RESULTS AND DISCUSSION 1 March 3363 5.2 Weather duringthe surveyswas mostly clear (Ta- 2 April 2726 4.2 ble 1); only one shortperiod of rain precludeddata 3 May 2369 3.6 4 June 3358 5.2 collectionalong a two km sectionof the route during 5 July 1649 2.5 June 1982. Wind speedwas consistentlylow (i.e., 6 August 1924 2.9 <20 kph) during the surveys.We founda moderate 7 September 2384 3.7 correlationbetween sky conditionsand number of 8 October 1917 2.9 vultures counted; i.e., fewer vultures was seen on 9 November 2141 3.3 cloudy than on clear days (rs = 0.3890, df = 18, 10 December 2037 3.1 0.05 < P < 0.10). A total of 7186 km were surveyed 11 January 1503 2.3 in 11 counts,with a total of 25 371 vulture sightings. Total 25 371 Mean 3.5 An averageof 2306.5 (+_623.19S.D.) vultures/survey were sighted(range = 1503-3363; Table 2), or an averageof about3.5/transect kilometer. Santana ruary (eggs),April (oldernestlings), and May (young et al. (1986a) reported substantiallyfewer vultures nestlings)(Davis 1941; Jackson 1983). Thus, low (meansfor four transectsegments ranged from 0.002- countsin July, Augustand Octoberwere not likely 0.9/km) from roadsidecounts in southwesternPuer- due to parental attendanceat nests. to Rico, as did Hubbard (1983) in New Mexico Vulture flight activity differed during the day. (0.03/km). Activity was low before 0800 H, and declinedsub- We notedpeaks in March, April and June num- stantiallyafter 1800 H (Fig. 2). Two peak periods bers of birds observed(Table 2). Counts were sub- of activity were observed:one between0900 H and stantially lower during the periods July-October 1200 H and a second between 1400 H and 1700 H. and December-January(ANOVA; F = 9.56, df = Number of vulturesobserved was inversely related 10, 66; P < 0.01). However, our small sample size to the distancefrom the transect line (rs = -0.900, (single monthly surveys)and the variation in sky P < 0.01). Observations of vultures declined sub- conditions do not allow a realistic evaluation of sea- stantially beyond200 m, suggestingthat detection sonal variation in vulture numbers.Sky conditions was less likely beyond that distance(Fig. 3). The were poor (completecloud cover) in January, and number of vultures observed within 201-400 m from only fair (mostlycloudy) during the Decembercount, the transect was about 32% less than the numbers which might explain the low numbersof birdscount- detectedin closerranges. Numbers of vultures ob- ed during thosesurveys. However, the weather was served within 401-600 and >600 m from the tran- goodto excellent(clear or mostlyclear) during the sectwere only 13.1% and 6.4% of the number we July-Octobersurveys (Table 1). AlthoughTurkey counted within 200 m. An alternative explanation Vultures have not been reported as migratory in to birds being lessdetectable at distances>200 m Cuba previously(Wilbur 1983), two birds marked may be that vultures concentratedalong roads for (patagialcolor streamers) in southFlorida havebeen food (i.e., road kills). A check study is neededto observednear La Habana (Wotzkow, pers.observ.). determineif vultures are clusteredalong roads and Such movements,along with possibl.elocal move- to verify error rates of placingobservations into dis- mentsin responseto seasonalfood distribution, may tance segmentsaway from the transectline. haveinfluenced local numbers of vulturesalong our Vulture abundance(and detectability)were ana- surveyroute. Breedingseason for Turkey Vultures lyzed among the six segmentsof the transectthat has not been clearly definedfor West Indies popu- reflected habitat differences. Vulture counts were lations, but nests have been found in Cuba in Feb- weighted to compensatefor reducedflying activity 6 CARLOSWOTZKOW AND JAMES W. WILEY VOL. 22, No. 1

35O LU 40 n" > '1- 300 rr uJ 03 U.I 250 rn 30 > o LU 200 rr 20 O 15o o o Z 100 I.- lO Z z •: 50 o

LU 0 0 0-100 101-200201-400401-600 >600 6 7 8 9 10 11 12 13 14 15 18 17 18 DISTANCE FROM ROAD (M) TIME (HR) Figure 3. Percent of Turkey Vultures (N = 25 371) Figure 2. Turkey Vulture activity, expressedas mean observedwithin fivedistance segments during number of birds (N = 25 371) observedper 11 surveysin Cuba, March 1982-January hour throughday during 11 roadsidesurveys 1983. in Cuba, March 1982-January 1983.

(thus increasedvisibility) before 0900 H, between 1700 H on cleardays; and 4) conductmore frequent 1200-1400 H, and after 1700 H. Vultures counted countswhich could be completedin a singleday. within the six regionsalong the surveyroute differed ACKNOWLEDGMENTS (ANOVA; F = 9.12, df = 6, 70; P < 0.01). Highest countsoccurred in segmentsthat had greater vege- We thank Mark R. Fuller, David Ellis, Kim Titus, Thomas M. Sweeney,Deborah Davis, and Patricia P. tative and physicalvariety (e.g., Alturas de Santa Rabenold for their expert reviews of the manuscript. Clara and Peniplanode Florida-Camagfiey-Tunas). Countswere lowestin the plainsand cultivatedareas. Santana et al. (1986a) also reportedfewer vultures LITERATURE CITED in agriculturalareas of PuertoRico. In our surveys ANDERSEN,D. E., O. J. RONGSTADAND W. R. MYTTON calculateddensity of observedvultures -<200 m of 1985. Line transectanalysis of raptor abundancealong the road was 0.06/ha (287 440 ha sampledin 11 roads. Wildl. Soc. Bull. 13:533-539. surveys). BROWN,W. H. 1976. Winter population trends in the Cuban vulture populationsare subjectto the same Black and Turkey Vultures. Am. Birds 30:909-912. factorsthat might adverselyaffect vulture popula- D^vIs, D.E. 1941. Notes on Cuban birds. Wilson Bull 53:37-40. tions in other regions (i.e., habitat modification, DOD, A. S. 1978. Aves de la Repfiblica Dominicana. chemicalpesticides, persecution, and to a lesserex- Museo Nacional Historia Natural, Santo Domingo, tentman-related accidents; reviewed by Wilbur 1983) RepfiblicaDominicana. 332 pp. and should be monitored. We recommend that vul- ELLIS, D. H., R. L. GLINSKI,J. G. GOODWIN,JR. AND ture surveysbe conductedat 5-10 yr intervalsto W. H. WH^LE¾. 1983. New World vulture counts detectchanges in populationlevels in Cuba. Road- in Mexico, Central America, and SouthAmerica. Pages sidecount methods appear suitable for thesesurveys. 124-133. In S. R. Wilbur and J. A. Jackson, EDS. However, we make the following recommendations Vulture biology and management.Univ. Calif. Press, for improving survey methods:1) conductcounts Berkeley. 550 pp alongregular transect routes throughout the year to FULLER,M. R. ANDJ. A. MOSHER. 1981. Methods of determine if seasonal fluctuations in numbers are detectingand countingraptors: a review. Pages235- 246. In C. J. Ralph and J. M. Scott,EDS. Estimating real; 2) if countsvary throughthe year, surveydur- numbers of terrestrial birds. Stud. Arian Biol. 6. 630 ing low count periods(e.g., January, July, August PP. and Octoberin this study)to excludepossible influx -- AND-- 1987. Raptor surveytechniques. of'migrants for a conservativepopulation estimate; Raptor ManagementTechniques Manual, Nat. Wildl. 3) conductsurveys between 0900-1200 H and 1400- Fed., Washington, DC. SPRING 1988 TURKEY VULTURES IN CUBA 7

GARRIDO,O. H. AND F. GARCIAMONTAiqA. 1975. Ca- 1978. South Texas region. Am. Birds 32:373- t•logo de las avesde Cuba. Acad. CienciasCuba, La 375. Habana. 149 pp. WETMORE,A. 1916. Birds of Porto Rico. U.S. Dept. HUBBARD,J.P. 1983. Roadside raptor counts as an Agric. Bull. No. 326. indicator of the status of the Turkey Vulture in New WILBUR, S.R. 1983. The status of vultures in the West- Mexico. Pages 375-384. In S. R. Wilbur and J. A. ern Hemisphere.Pages 113-123. In S. R. Wilbur and Jackson,EDS. Vulture biologyand management.Univ. J. A. Jackson,EDS. Vulture biologyand management Calif. Press,Berkeley. 550 pp. Univ. Calif. Press,Berkeley. 550 pp. INSTITUTO CUBANO DE GEODESIA Y CARTOGRAF•A. 1978. ZAR, J. H. 1974. Biostatisticalanalysis. Prentice-Hall, Atlas de Cuba. La Habana, Cuba. 168 pp. Inc., EnglewoodCliffs, NJ. 620 pp. JACKSON,J.A. 1983. Nesting phenology,nest site se- lection,and reproductivesuccess of Black and Turkey Vultures. Pages245-270. In S. R. Wilbur and J. A. Addressof first author: Calle K no. 15016 el7 y D Altahabana, Ciudad de La Habana, 8, Cuba. Ad- Jackson,EDS. Vulture biologyand management.Univ. dress of second author: U.S. Fish and Wildlife. Ser- Calif. Press,Berkeley. 550 pp. SANTANA,C. E., G. A. POTTERAND S. A. TEMPLE. 1986a. vice, PatuxentWildlife ResearchCenter, La•urel, Status and seasonalpattern of abundanceof Turkey MD 20708. Mailing addressof secondauthor: Cal- Vultures in Puerto Rico. J. Field Ornithol.57:235-238. ifornia ResearchStation, 2291-A Portola Road, Suite $00, Ventura, CA 93003. , AND-- 1986b. Home range and activity patterns of Turkey Vultures in Puerto Rico. Received6 July 1987; accepted5 November 1987 Caribb.J. Sci. 22(3-4):175-177. WEBSTER,F. S., JR. 1975. South Texas region. Am. Birds 29:711-714.