Conservation Status of Birds of Prey in the South American Tropics
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j. RaptorRes. 32 (1) :19-27 ¸ 1998 The Raptor ResearchFoundation, Inc. CONSERVATION STATUS OF BIRDS OF PREY IN THE SOUTH AMERICAN TROPICS RICHARDO. BIERREGAARD,JR. Departmentof Biology,University of North Carolinaat Charlotte,9201 UniversityCity Blvd., Charlotte, NC 28223-9201 U.S.A. ABSTRACT.--TheICBP/IUCN Red Data Book listsas Threatened or Endangered five of the 82 species of Falconiformes and one of the 32 Strigiformes that breed in tropical South America. The White- collared Kite (Leucopternisforbesi), an endemic of the Atlantic coastalforests of Brazil, can be added to this list. Becausevast areas of South America, most notably its tropical forests,have been inadequately surveyedand few studieshave been carried out on raptor speciesor assemblages,our knowledgeof the distribution and natural history of many raptor species,especially owls and forest-dwellingFalconifor- mes, is rudimentary at best. Most needed for conservationpurposes is information on population den- sities,distribution, and reproductivebiology that will tell us how large populations are and how fast they can reproduce. For most species,these data are anecdotal or nonexistent.Although the majority of South America's tropical raptors appear not to be globally threatened at present, more information is needed to confirm current assessments,recognize when speciesbecome threatened, and to move quickly and efficiently to addresssuch threats. KEYWORDS: Falconiformes;Strigiformes; endangered species; habitat loss; South America; tropical forest;, conser- vation. Estado de conservacionde las avesrapaces en los tropicos de Am6rica del Sur RESUM•N.--E1Libro Rojo de la ICBP/IUCN incluye coxnoamenazadas o en peligro a cinco de las 82 especiesde Falconiformesy una de las 32 Strigiformes que se reproducen en los tr6picos de Aan6rica del Sur. Leucopternisforbesi,endSmica de los bosquescosteros del Atl•tnticoen Brasilpuede ser adicionada a esta lista. Vastasfireas de Sur•unerica,mas especificamentelos bosquestropicales han sido inadecu- adamente investigadosy pocos estudioshan sido realizados sobre las especiesde avesrapaces o sobre susensamblajes, nuestro conocimiento de la distribuci0n e historia natural de muchas especiesde aves rapaces,especiahnente buhos y Falconiformesde bosque,es rudimentario. Para prop6sitosde conser- vaci0n se requiere de informaci6n relacionada con densidadespoblacionales, distribuci6n, biolog•a reproductiva, que pueda decirnos de que tamafio son las poblacionesy que tan r•tpido se pueden reproducir. Para la mayorCade las especiesestos datos son anecd6ticose inexistentes.A pesar de que la mayoria de las avesrapaces de Am6rica del Sur no esfftnglobahnente amenazadasen el presente, se requiere de mas informaci6n para confirmar las evaluacionesactuales y poder reconocer cuando una especiese encuentra en peligro y poder actuar r•tpidamente para en forma eficiente abordar las amen- azas. [Traducci6n de C6sar Mfirquez] The South American continent is renowned for are found primarily south of the tropicsbut have its avian diversity;roughly 32% (3100 species)of rangesthat extendinto the tropics(north of 30øS). the world's avifauna is found there, on only 12% Not coincidentally, South America is also re- of the world's land surface. Birds of prey are no nowned for its Amazonian rainforests, home to exception. Eighty-fourFalconiformes and 32 Strio many of the continent's remarkable avifauna. giformesare resident in South America (following Among the raptors, 52 Falconiformesand 25 owls the taxonomyin Hume [1991] and de1Hoyo et ai. are associated with some sort of tropical forest, [1994]). These totalsrepresent 28% and 21%, re- from the lowlandsto high-altitude cloud forests. spectively,of the world's speciesin these two or- Tropical forests around the world are being ders. Most (82) of the Falconiformes(Appendix 1) clearedat alarmingrates (Whitmore 1997), with an and all of the owls (Appendix 2) are tropical or inevitable loss of primary habitat and fragmenta- 19 20 BIERREGAARD VOL. 32, NO. 1 tion of what remains. These landscape-wide tion has hardly been studied in the South Ameri- changeshave profound implicationsfor the con- can tropics. Including subspecies,the 82 Falconi- servation of biological diversityand have piqued form speciesin South America representonly 128 the attention of biologistsfrom the conservation strictly South American taxa. Most species are community(e.g., Lauranceand Bierregaard1997). monotypic and four speciesalone account for 22 Although the loss of tropical forests is the most of these taxa (Appendix 1). The constraintof only conspicuousthreat to tropical species,the conver- considering South American forms is clearly arti- sion of wooded or open savannato intensive agri- ficial since many of the speciesoccur in Central culture is also taking its toll by reducing available America, Mexico, and the Caribbean,where many habitat. are representedby variousdistinct populations. In- Birds of prey, as top-order predators with large cluding Central American, Mexican, and Caribbe- home ranges and generally low population densi- an populations,the number of taxa representedby ties, may be especiallysensitive to suchhabitat loss the 82 speciesclimbs from 128 (1.6 taxa/species) and fragmentation. Due to this, certain taxa may to 170 (2.1 taxa/species)(Appendix 1). Hence, the be important indicatorsof habitat integrity.Along much smaller Central American region containsa with their high visibility and general allure, they great deal of biologicaldiversity and is of great con- are ideal "flagshipspecies" for the conservationof servation concern, particularly given the greater critically endangered habitats. annual rate of deforestationthere when compared In this paper, I review the aspectsof the biology to tropical South America (Whitmore 1997). of tropical speciesthat I feel need to be better un- Data on reproductive biology such as behavior, derstoodif we are to assessaccurately their conser- clutch size, frequency of nesting attempts, survi- vation status,and then I briefly summarizethe ar- vorship of nestlings,and recruitment into the adult eas where our knowledge is weakest.Within this population can provide an estimate of a species' framework, I discussthe principal threats to raptor potential rate of population growth. Combined speciesin the South American tropics, review the with estimatesof population size or density,these general trends that are apparent, discussthe status data are important in assessingthe potential resil- of eight speciesthat seem to merit special atten- ience of a population. tion, and make recommendations for future re- Finally, information on each species'habitat re- search. quirementswill also help us to assessthreats to its persistence.Not all speciesthat are typicallyfound DATA NEEDED in any given habitat are behaviorallyor ecologically Effective conservation must be based on a sound restricted to it. A number of North American rap- understanding of a number of biological factors, tors have shown great behavioral plasticityand are principally but not exclusively: distribution and nesting in suburban (e.g., Merlins [Falcocolumbar- population density,taxonomy, breeding behavior ius; Sodhi et al. 1991], Swainson's Hawks [Buteo and reproductive rates, and habitat requirements, swainsoni;England et al. 1995], Cooper's Hawks or, conversely,sensitivity to habitat modification. [Accipitercooperii; Rosenfield et al. 1995]) or urban Information on migratory habits and prey special- (Peregrine Falcon [Falco pereg,inus])settings. In ization is important as well. Distribution and pop- Central America, a number of raptorsnest in both ulation density together provide an estimate of primary forest as well as more disturbedlandscape population size,which is crucial in monitoring the mosaics of agriculture, second growth, and pri- vulnerability of a species. mary forest (Whitacre pers. comm.). Although it is not often considered in conser- DATA IN HAND vation discussions,our understanding of taxonomy at the specific and subspecificlevel is indeed im- A recent review (Bierregaard 1995) highlighted portant. In fact, we face many problems in defining the gaps in our knowledge of the natural history biological and phylogeneticspecies and in decid- of the Falconiformes in Meso- and South America. ing how to deal with distinct populations (Zink and Overall, the specieswe know the least about are McKitrick 1995). These questions have conserva- the small residents of primary forest, especially tion implications becauseconservation laws focus those in the genera Accipit• Leucopternis,and Mi- at only the specieslevel. crastur.Nests have not been described for 16 spe- Among Falconiformes, subspecific differentia- cies (Table 1), and fewer than five nests have been MARCH 1998 RAPTORSIN SOUTH AMERICAN TROPICS 21 Table 1. South American Falconitbrmeswith very poorly known natural histories. UNKNOWN BREEDING SCANT OR No PREY NEST UNDESCRIBED BIOLOGY DATA a Leptodonforbesi x x 0 Ha,pagus diodon x + Circusbuffoni + Accipiterpoliogaster x x 0 Accipitersuperdliosus + Accipitercollaris x x 0 Accipiterventmlis x + Accipitereryth,vnemius x x 0 Leucopternisschistacea x x Leucopternisplu mbea x x + Leucopternisprinceps x x + Leucopternismelanops x x + Leucopterniskuhli x x + Leucopternislacernulata x x Leucopternispolionota x x Buteogallussubtilis + Ha,pyhaliaetussolitarius + Harpyhaliaetusco,vnatus Buteoalbigula x + Buteo ventralis x + Phalcoboenus carunculatus x Phalcoboenusmegalopterus x Phalocoboenusalbogularis x + Milvago chimachima