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

The processes of bird diversification in South America have long been a focus of evolutionary biologists and this paper partly acts as an introduction to a selection of such work published in the Biological Journal of the Linnean Society and collated into a Virtual Issue (http://wileyonlinelibrary.com/bij/neotropical-bird-evolution). At the beginning of the 20th century, Frank M. Chapman, curator of birds at the American Museum of Natural History, conducted a series of expeditions in Colombia and Ecuador to ‘discover the geographic origins of South American bird‐life’. The expeditions produced almost 30 000 specimens, obtained in a sampling scheme aimed at revealing the geographical and elevational distributions of birds. Chapman proposed a series of ideas about the evolutionary origins of the tropical Andean avifauna. Despite being nearly 100 years old, Chapman's evolutionary hypotheses on the role of the appearance of new environments and geographical barriers on speciation, have an enduring influence. With the development of molecular methods and tools for the study of the mechanisms and timing of speciation events, Chapman's hypotheses have seen a revival in the recent scientific literature. Recent work has provided support for some of Chapman's hypotheses, but has also revealed greatly complex processes of biotic differentiation in the Neotropics. What is remarkable is that with means that today seem precarious, Chapman envisioned evolutionary processes at a continental scale that remain valid, in fields that currently advance at an accelerated rhythm and soon render older ideas obsolete.