Central America is a region of great avian diversity, and the highlands of Costa Rica and Panama are particularly rich in endemic bird species. Continuing deforestation has destroyed large parts of the birds' natural habitats in this region. The ability of birds to use non-forest habitats will ultimately determine their vulnerability to further deforestation, and knowledge of their habitat use is therefore essential in planning conservation strategies. We examined the effects of deforestation on the abundance of restricted-range bird species in the southern Costa Rican part of the Talamanca mountain range. We used line-transect distance sampling to obtain densities in forest and non-forest habitats. Most (22/28) restricted-range species were recorded in forest and non-forest. Of 28 restricted-range species, 13 species showed a clear preference for forest and 8 for non-forest, and total numbers were one-and-a-half times higher as high in forest compared with non-forest. Of the 10 most common species, one was more abundant in non-forest and seven were more abundant in forest. We conclude that forest is the primary habitat for the majority of the restricted-range avifauna, and their dependence on forest makes them particularly vulnerable to deforestation. Adequate protection of the forests in these mountains is therefore the best assurance of the long-term survival of these birds.