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

No abstract

2016-12-24T18:13:07

AimThe decrease in species richness with increasing elevation is a widely recognized pattern. However, recent work has shown that there is variation in the shape of the curve, such that both negative monotonic or unimodal patterns occur, influenced by a variety of factors at local and regional scales. Discerning the shape of the curve may provide clues to the underlying causes of the observed pattern. At regional scales, the area of the altitudinal belts and mass effects are important determinants of species richness. This paper explores the relationship between bird species richness, elevation, mass effects and area of altitudinal zones for birds in tropical mountains. LocationThe three Andean ranges of Colombia and the peripheral mountain ranges of La Macarena and Santa Marta. MethodsLists of bird species were compiled for altitudinal belts in eastern and western slopes of the three Andean Cordilleras and for La Macarena and Santa Marta. The area of the altitudinal belts was computed from digital elevation models. The effect of area was analysed by testing for differences among altitudinal belts in the slopes and intercepts of the species-area relationships. Mass effects were explored by separately analysing two sets of species: broadly distributed species, i.e. lowland species whose distributions extend into the Andes, and tropical Andean species, i.e., species that evolved in the Andes.

The rarity of an organism is widely accepted as a good predictor of vulnerability, but rarity has been interpreted in a variety of ways. Rabinowitz et al. (1986) defined three dimensions of rarity for an analysis of the flora of the British Isles geographic distribution, habitat specificity, and local population size. They found the three factors to be independent, that is, each factor provides information not provided by the other two. In this paper, the method of Rabinowitz et al. is used to analyze the vulnerability of the cloud forest avifauna of the Cordillera Central of Colombia The method is extended by assigning a vulnerability index to each form of rarity and analyzing its taxonomic and ecological correlates. I found that the three factors are not independent. Species with wide geographic distribution tend to have broad habitat specificity and high population densities. One‐third of the species have low population density, and most of these have restricted habitat specificity and narrow geographic ranges. Forty‐five percent of the birds in this sample are highly vulnerable because they have narrow distributions and require forest habitats. The taxonomic and ecological analyses reveal that some groups of species are particularly vulnerable. Among insectivorous birds, woodcreepers, spinetails, and antbirds seem to be very vulnerable becuse they depend on forest habitats. Raptors show no clear pattern, but for frugivores a clear pattern emerges. Some families (e.g., parrots, cotingas), seem to be consistently vulnerable, independent of body size. Tanagers show a significant correlation between body size and vulnerability. An analysis of local vulnerability (determined by habitat specificity and population size, regardless of distribution) reveals that frugivorous birds of restricted habitat specificity are significantly larger. Similar findings have been reported by other studies. The three‐dimensional classification of rarity used in this study provides a rapid, albeit preliminary, approach to identifying vulnerable species. To develop management practices adapted to each particular case, careful analysis of life history traits and detailed population and community studies are required.