Although the Guinea-Congolian rain forest region is an important focal point for conservation in Africa, very little information is available on the effects of forest modification and land use on the region's biodiversity. We studied bird communities and vegetation characteristics in 24 sampling stations distributed over two near-natural forests (near-primary forest, secondary forest), and two land use types (agroforestry, annual cultures) in the lowlands of the Korup region, Cameroon. Repeated sampling was used to establish near-complete inventories of bird assemblages for each site. Despite a 90% average drop in tree basal area from forest to farmland, overall bird species richness did not decrease significantly with increasing habitat modification. However, different groups of birds responded in different ways. Frugivorous and omnivorous bird species richness did not differ between habitats, whereas richness in granivorous, flower-visiting, and nonbreeding species was higher in land use systems compared to forests. In contrast, insectivorous birds, especially terrestrial and large arboreal foliage gleaning insectivores, and ant followers showed a declining species richness from forest to farmland. Also, richness in species of those restricted to the Guinea-Congolian forest biome and of the family Pycnonotidae showed a pronounced decline with increasing habitat modification. Species richness of overall insectivores, terrestrial insectivores, large-and medium-sized arboreal foliage gleaners, ant followers, as well as pycnonotids and biome-restricted species, were strongly or even very strongly positively correlated with overstory tree density and, in most cases, also with basal area. In contrast, tree density and basal area were strongly negatively correlated with species richness of nonbreeding visitors and flower-visiting bird species. Species composition was most distinct between near-primary forest and annual culture sites, and the abundance of 23 out of 165 species was affected by habitat, suggesting considerable partitioning of habitat niches along the habitat gradient. Our results stress the importance of tree cover in tropical land use systems for the maintenance of resident forest bird populations and confirm that natural forest management is more beneficial for global bird conservation compared to other forms of forest exploitation, including agroforestry systems.

Vegetation surveys were carried out at 24 sampling stations distributed over four land use types, namely near-primary forest, secondary forest, agroforestry systems and annual crop lands in the northeastern part of the Korup region, Cameroon, to assess the impact of forest conversion on trees and understorey plants. Tree species richness decreased significantly with increasing level of habitat modification, being highest and almost equal in secondary and nearprimary forests. Understorey plant species richness was significantly higher in annual crop lands than in other land use types. The four land use types differed in tree and understorey plant species composition, the difference being smaller among natural forests. Tree and understorey plant density differed significantly between habitat types. Density was strongly correlated with species richness, both for trees and understorey plants. Five tree and 15 understorey plant species showed significant responses to habitat. A 90% average drop in tree basal area from forest to farmland was registered. Our findings support the view that agroforestry systems with natural shade trees can serve to protect many forest species, but that especially annual crop lands could be redesigned to improve biodiversity conservation in agricultural landscapes of tropical rainforest regions.