Distributional Changes in the Colombian Avifauna: A Preliminary Blue List

Abstract

Some important man-caused changes in the distributions of Colombian bird populations are discussed. Examination of the changes is based on a preliminary Blue List of 135 species with declining populations. Canopy frugivores dominate the list, followed by terrestrial and aquatic species, respectively. There are proportionately more highland species on the list than lowland species. Two regions, the central Colombian highlands, and the Cauca-Magdalena lowlands contain more declining species than other avifaunal regions. Almost two-thirds of Colombia's endemic species have been placed on the list. Some species have profited from deforestation or other human activities, and these are discussed. RESUMEN. Se discuten algunos cambios importantes, causados por el hombre, en las distribuciones de poblaciones de aves colombianas. El reconocimiento de los cambios esta basado en la Lista Azul preliminar de 135 especies con poblaciones en disminuci6n. Los frugivoros del tope del bosque dominan la lista, seguidos respectivamente por especies terrestres y acuaticas. Proporcionalmente en la lista hay mas especies de tierras altas que de tierras bajas. Dos regiones, las tierras altas del centro de Colombia y las tierras bajas de Cauca-Magdalena, presentan mas especies en disminucion que otras regiones de avifaunas. Casi dos tercios de las especies endemicas de Colombia estan incluidas en la lista. Se discute tambien la ganancia que obtuvieron otras aves por la deforestation y otras actividades humanas. In this paper I examine changes in the distributions of Colombian bird populations. Olivares (1970) and Lehmann (1970) discussed some effects of environmental change on birds in Colombia and mentioned examples of species that have profited or been harmed by these changes. However, neither author attempted to provide a comprehensive overview of the country's avifauna. Some of Colombia's endangered or threatened species are discussed in the International Council for Bird Preservation (ICBP) Bird Red Data Book (King 1981). Unfortunately, little other information has been compiled on distributional changes of Colombian birds. Furthermore, bird populations in Colombia (or most anywhere in developing regions of the world) are not systematically surveyed or evaluated like they are through the Blue List for North America (Arbib 1971), the Christmas Bird Counts, or more recently the natural heritage inventories of The Nature Conservancy. There is no systematic research on endangered Colombian species either by government or private agencies. In order to examine distributional changes in Colombia's avifauna a preliminary Blue List was prepared. This list is similar in concept to that initiated in North America in 1971 by Robert Arbib (Arbib 1971). The latter list, updated annually, includes North American birds that are of special concern because they appear to be ... giving indications of non-cyclic population decline or range contractions, either locally or widespread (Arbib 1971). Species on the list may be fairly common locally, or even widespread, but because of habitat reduction, chemical contamination, hunting pressure, or other causes, their populations appear to be in decline. As noted by Arbib (1971, 1972) the Blue List is essentially an early warning system that focuses attention on problem species and may help alert the scientific community, government agencies, and the public to situations where action is needed. I include on the present list (Table 1) most species whose geographical ranges in Colombia are believed to have declined by at least 50 percent. Unlike the North American Blue List, I also include all endangered species listed by the ICBP Bird Red Data Book (King 1981) because information on these species is scarce. I exclude species known only from one or a few localities near the Colombian border, or species known only from Bogota specimens without precise locality (Meyer de Schauensee 1 948). I also exclude a considerable number of species whose ranges probably have contracted by 50 percent or more due to deforestation since pre-Colombian times but that still occur commonly wherever tracts of forestland remain. Examples of species in this