We report on the extent of bird extinctions at San Antoni¢~ a fragmented cioud forest site in the western Andes of Colombi~ for which surveys dating back to 1911 and 1959 are available. In 1911 forest bird species were present in San Antonio. Twenty-four species had disappeared by 1959, and since then 16 more species have gone locally extincg for a total of 40 species or 31% of the original avifaumt We analyzed patterns of extinction in relation to geographic distribution and foraging guild~ We found that in this montane assemblag~ being at the limits of the altitudinal distribution was the main correlate of extinction; 3 7% of the extinct species were at the upper limit of their altitudinal distribution We also found that the most vulnerable guilds were the understory insectivores and the large canopy frugivorex Our study illustrates the extent of bird extinctions that are currently undocumented in the highly fragmented forests of the northern Ande~ where the absence of baseline information on the fauna of unaltered forests is a limiting factor for the development of conservation and management planx We stress the need to establish data bases and long-term monitoring projects for the Andean fauna * Present address. NYZS The Wildlife Conservation Society, Apartado 1845, Calg Colombia

SummaryHistorical and anecdotal data indicate that out of 14 original species of resident diurnal raptors, six have become extinct and two more are considered endangered in the middle Cauca Valley, Colombia. While the decline of several species is related to a drastic reduction of original habitats such as forests and wetlands, three open-habitat species have also suffered population declines. Possible causes include the recent expansion of intensive agriculture (at the expense of cattle-ranching areas), agrochemical pollution, hunting, and factors such as body size, the proximity of the valley to the upper altitudinal limit of most of the affected species, and the relative isolation of the valley from the Caribbean region and the savannas east of the Andes. The need for monitoring projects s i stressed for the vertebrate fauna, including those species considered common in open and disturbed habitats.Informaciones históricas y anecdóticas indican que de una fauna original de 14 especies de aves rapaces diurnas residentes en el valle medio del rio Cauca, Colombia, se han extinguido seis especies y dos mas se consideran amenazadas. Mientras que la disminucion de algunas especies se relaciona con la drástica reductión de hábitats originales tales como bosques y humedales, tres especies propias de hábitats abiertos también se han visto afectadas. Se identifican como probables factores la expansión de la agricultura intensiva (a expensas de las areas previamente dedicadas a la ganaderia), la contaminatión por agroquimicos, los conflictos con los intereses humanos y ciertos factores como el tamano corporal, la proximidad del valle medio del Cauca al limite superior de distributión altitudinal de estas especies y el relativo aislamiento del valle con respecto de la región del Caribe y de las sabanas al oriente de los Andes. Se relieva la necesidad de establecer programas de monitoreo de las faunas de vertebrados, inclufdas las especies consideradas como comunes en hábitats abiertos y perturbados.

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