Our knowledge on the nature of forest species responses to deforestation remains ambiguous. Moreover, most previous research took place in fragmented landscapes or did not take into account the diversity of ecological features among the studied species. Understanding the relationship between forest cover and functional guilds inside a bird community may serve as a valuable tool to assess how much forest is necessary to conserve significant portions of forest species. We sampled birds (198 species, 6 883 encounters) along a full gradient of deforestation across 4 000 km² of forest-dominated landscapes in Southwest Cameroon. We applied multivariate adaptive regression splines to model α-, β-and γ-richness of various bird guilds in relation to forest cover. Overall, β-and γ-richness remained constant above 42% forest cover. However, total α-richness as well as all richness partitions of Guinea-Congo biome-restricted, large-bodied arboreal foliage gleaning, tree nesting, and frugivorous species declined when forest cover was below 74%. Moreover, ant-followers and terrestrial insectivores showed their highest diversity at zero deforestation. In contrast, open-land, granivorous, opportunistic insectivorous and widespread species strongly increased below 42% forest cover. High β-diversity at intermediate deforestation conditions indicate that the sharp decline of original forest bird diversity may only be compensated by habitat and 2 foraging generalists, which benefit from high habitat heterogeneity. Our study implies that Afrotropical forest bird diversity decreases non-linearly with forest loss. Critical habitat thresholds above 70% are much higher than previously reported and highlight the need for conservation measures of large intact forest remnants.

Many integrated conservation and development projects use road construction to induce a shift in income activities, since road access can reduce both poverty and environmental degradation. There is, however, little empirical evidence on the effects of road access on income patterns. We contribute to existing literature by analyzing the effects of road access on income activity choice in Korup National Park, Cameroon using a difference-in-difference approach. Road access led to a rise in total household income by 38% due to higher household participation in self-employment and wage labor. We neither found an effect on income from crop farming nor on participation in hunting activities. The effects of road access can be diverse and unforeseeable. Road construction in protected areas should thus be carefully considered and planned and only be implemented when other options are not feasible.

SummaryThe Congo Grey Parrot Psittacus erithacus has experienced a severe population breakdown in recent decades. The rainforests of the Korup region in Southwest Cameroon may harbour a large population of this species, but density and population estimates from this area remain controversial. Before the 2016 breeding season, we surveyed Grey Parrots along transects (621.1 km survey effort) in three adjacent landscape types: primary forest in Korup National Park (KNP), smallholder agroforestry matrix (AFM), and industrial oil palm plantation (OPP). We also collected information on the trees used for nesting, feeding and roosting. Using Distance analysis, we estimated relatively low densities of stationary flocks, ranging from 0.30 ind./km2 in KNP, over 0.82 ind./km2 in OPP to 2.70 ind./km2 in the AFM. Parrots were observed feeding or roosting in 17 tree species, of which 15 were located in AFM alone. Feeding was most often observed on cultivated Elaeis guineensis and Dacryodes edulis, but never in maize. The detected parrot densities probably reflect declines within the period 2008–2016, suggesting that the species’ recent IUCN uplisting to ‘Endangered’ and transfer to CITES Appendix I was indeed justified. Our results also suggest that traditional smallholder agroforestry may play a role in habitat conservation strategies, since these forms of cultivation may maintain important breeding and feeding opportunities for Congo Grey Parrots.

Callitrichids can persist in secondary forests where they may benefit from elevated prey abundance. However, how tamarins forage for prey in secondary forest compared to primary forest has not been examined. Using scan and focal sampling, we compared prey foraging and capture success of two groups of Saguinus nigrifrons in north-eastern Peru: one ranging in primary forest, the other with access to a 10-year-old anthropogenic secondary forest. There was a trend for more prey search in the secondary forest, but prey feeding, capture success and size were lower compared to the primary forest. Tamarins avoided the forest floor, used vertical supports less often and searched on a lower variety of substrates in the secondary forest. In the secondary forest, tamarins did not capture flushed prey, which make up a substantial part of the total prey captures biomass in primary forests. Reduced prey capture success is unlikely to reflect reduced prey availability, since more Orthoptera were found in secondary forest through ultrasonic surveys. Therefore, the prey search activity of S. nigrifrons in young secondary forests seemed rather opportunistic, presumably influenced by altered predation patterns, vegetation structure, as well as prey diversity.Electronic supplementary materialThe online version of this article (doi:10.1007/s10329-014-0416-4) contains supplementary material, which is available to authorized users.