Despite the fact that West African tropical forests are the most fragmented in Africa, there has been no published research on biodiversity in these fragments. To determine how forest birds respond to five factors—patch size, patch isolation, canopy density, abundance of large trees, and proximity to forest edge—in these forests, we surveyed 60 species of forest birds on 121 transects (2.5 ha each) in 35 forest fragments in the semideciduous forest zone of Ghana. Species richness per transect increased with patch size over the entire range of patch sizes observed (3–33,000 ha). The diversity of forest birds (22 species) on a single transect in a large forest patch was similar to the cumulative diversity (25 species) on all 17 transects in 13 small patches. Twenty‐two of 60 species were area sensitive, 15 of which were never found in small patches. These results suggest that only large forests will conserve many species of West African forest birds. Nine species were edge sensitive, 7 of which were also area sensitive. However, forest structure near patch edges was not consistent with bird responses to canopy and tree density, suggesting that mechanisms other than microclimate or structural changes ( perhaps predation or nest parasitism) underlie the response of most species that are sensitive to both edge and area. Regression of critical patch size (the smallest patch size in which a species was detected) on logarithm of body mass (an index of home range size) for 22 area‐sensitive species suggests that area‐sensitive species are unlikely to occur in patches smaller than several home‐range areas. Canopy density influenced 13 species (11 positively, 2 negatively), and abundance of large trees influenced 8 species (3 positively, 5 negatively). Forest birds did not respond to isolation (distance from a patch to a large forest) for isolation distances of 1–25 km, suggesting that island biogeographic mechanisms had less influence on birds than other potential mechanisms of area sensitivity. Although small patches contributed little to the conservation of forest birds—species found in small patches were well represented in large patches—small patches are probably important for supporting generalist bird species that provide ecological services in the agricultural matrix and serving as nuclei for future ecosystem recovery.

We explore the factors influencing the abundance of Colobus vellerosus in 11 forest fragments [Boabeng-Fiema Monkey Sanctuary and 9 surrounding forest fragments (range: 3.2-190 ha)] in the forest-savanna transition zone of Ghana. We used a ‘complete' count for the colobus census in the fragments. We determined the fragment sizes using geographic information system methods and assessed forest fragment quality (tree species richness). Colobus individuals were absent from 4 forest fragments but present in 7 (densities of 0.13/ha-1.63/ha). We modelled colobus density using Poisson regression and selected models based on corrected Akaike information criterion model weights. Fragment size and tree species richness in the fragments were positively associated with colobus density, whereas isolation distance of the forest fragments (range: 20-5,632 m) was negatively associated with colobus density. Our analysis suggests that the isolation distance between the fragments and Boabeng does impede colobus movement. As the colobus populations in Boabeng and Fiema increase, some of the unoccupied fragments may become more attractive to dispersing monkeys. Management measures that aim at increasing tree species richness within fragments, while maintaining some large trees between fragments, might help to increase the occupancy of some of the fragments that currently have no permanent colobus groups.

In tropical forests, most individual fruit-bearing trees depend on frugivores for seed dispersal (Howe & Smallwood 1982, Wilson 1992). Seed dispersal enhances germination potential, provides an opportunity for seeds to escape predation under the parent plants, and reduces seedling numbers under parent trees (Şekercioğluet al. 2004). The way frugivores handle seeds and process them may influence the seed fate of many plants (Janzen 1971). The quantity of seeds dispersed and the quality of dispersal provided by frugivores impact plant fitness (Herrera & Jordano 1981). Schupp (1993) defined the effectiveness of seed dispersal by frugivores as an empirical measure of quantity of seeds dispersed and quality of dispersal from the parent plant to a suitable microsite. Seed dispersal by frugivores increases the chances for seedling survival away from the vicinity of the parent plant because in tropical forests seed predation is concentrated under adult trees that prevent seedlings from establishing near parent trees (Howe & Miriti 2004).