1. The avifauna of the Bossematié Forest, an isolated and heavily logged Forêt Classée of 216 sq. km size in south-east Côte d’Ivoire, was studied five years after the last logging operations. The avifauna was censused by standardised mist-netting and spot-mapping on a 110ha study plot including different compartments: a tree plantation, a disturbed compartment with a swamp forest area and a liberation thinning area, as well as a less disturbed control compartment. The impact of the forest management on the bird community and the vegetation structure was assessed. In addition, the overall status of the vegetation in the forest was surveyed from sixteen 2-km line transects.
2. In 1996, the forest had the typical appearance of a residual forest. 61% of its surface consisted of young secondary growth with mono-layered canopy on low levels, only 24%
contained a multilayered canopy and 13% of its surface were gaps.
3. The percentage of gaps was significantly higher, but the percentage of older succession stages was lower in the liberation thinning compared to the control area. Size and density of overstorey trees (>10 cm dbh) seemed to remain unchanged by liberation thinning, but the density of understorey trees (5-10 cm dbh) increased significantly.
4. A five-years old Terminalia plantation consisted of an even-aged stand with a closed canopy, tree sizes were comparable to those in the control compartment, but trees were significantly more distant from each other. In addition, there was a definite lack of understorey vegetation due to repeated manual clearing.
5. Natural forest in the swamp forest area had a significantly lower size of overstorey trees, but neither their dispersion, nor the density of understorey trees (5-10cm girth) was significantly different from the control compartment (mid- or higher-slope level).
6. A total of 236 bird species was recorded in the Bossematié area, including observations from the surrounding. Overall avifaunal composition in the Forêt Classée was very similar (Soerensen=0.92) to that in the Bia National Park, Ghana, and this comparison is based on a species list from 1976, when most of the Bia reserve was still unbroken primary forest. 113 bird species belonged to the biome-restricted assemblage of the Guinea-Congo Forests Biome, which constitutes 61% of all Guinea-Congolian species known from Côte d’Ivoire.
Four Upper Guinean endemics were found, unconfirmed records of two additional ones exist. One more, the White-brested Guineafowl Agelastes meleagrides, formerly occurred in the area, but has not been recorded after the logging operations. Five bird species are officially classified as species of conservation concern in Côte d’Ivoire. A striking difference between the bird fauna of the Forêt Classée and the surrounding area wa found: 70% of the species present inside the forest (110 out of 159 spp.) were never recorded in the surrounding farmland.
7. Alpha-diversity and evenness of understorey birds from mist-net data within 2-ha areas were lower than in lowland primary forests of Côte d’Ivoire (Nimba) and Sierra Leone (Gola), but comparable to other, only slightly disturbed lowland areas in Côte d’Ivoire (Mabi forest reserve).
8. 118 bird species in 709 pairs were found to be resident on the 110 ha study plot during a three months census (June-August 1997). Extrapolated species richness for the 110 ha plot
was estimated at 136 to 139. The same number of species, namely 136, was the total number recorded on the plot during the whole thirteen months study period.
9. The community was dominated by four species occupying lower forest strata: Yellow-whiskered Greenbul Andropadus latirostris, Brown Illadopsis Illadopsis fulvescens, Green Hylia Hylia prasina and the Olive Sunbird Nectarinia olivacea. The abundance distribution did not differ significantly from the log-normal distribution. However, the proportion of”very rare” (< 0.25 pairs/100 ha) species was much elevated, the difference from log-series distribution only slight. Evenness was lower than in the broken-stick communities of Amazonian primary lowland forest.
10. Breeding pair densities were principally related to the species’ vertical stratification, not to their geographic range. In an interspecific comparison, there was a significantly negative correlation between foraging height and density. There was no correlation between the size of geographic range and abundance, Guinea-Congolian (excluding Upper Guinean endemics) and African Forest species showed both rare and common species, Upper Guinean restricted and ubiquitous species showed low overall densities. However, comparing densities with relative abundance data from primary forests, a higher percentage of the Upper Guinean endemics and Guinea-Congolian species showed lower densities than in primary forest, whereas the same was found in only few African Forest but not in ubiquitous species. Likewise, most hornbills showed lower densities than in primary forests.
11. 63 bird species were members of mixed species flocks. Flocks tended to be smaller and seemed to consist of fewer species than those known from unlogged forests. Species of the understorey and lower midstrata tended to be more regularly encountered in mixed flocks than species of higher strata.
12. On a small scale (18.3 ha), species richness and diversity of birds did not differ significantly between liberation thinning and control. However, species richness and diversity on 32 ha level was lower in the liberation thinning area. Species abundance patterns did not differ between control, liberation thinning, swamp forest and plantation and were not significantly different from log-normal nor log-series models.
13. Species composition changed markedly on a small scale (18.3 ha) between control, liberation thinning, swamp forest and plantation. Turnover was higher between control and swamp forest or plantation than between control and liberation thinning.
14. In interspecific comparisons, habitat preferences were best explained by the species’
geographic range, while diet, body size or vertical stratification were not related to habitat selection. Whereas an equal proportion of Guinea-Congolian (excluding Upper Guinean) species preferred/avoided the liberation thinning area, more African Forest species than expected preferred this area. Ubiquitous species reached highest abundances in the tree plantation. Most pycnonotid species showed highest abundances in the control compartment, while in sylviid species, no specific vegetation type was preferred.
15. Understorey birds were mist-netted in successively larger (nested) areas of the control and the disturbed compartment. Species richness and diversity of understorey birds on a small scale (2 - 8 ha) were higher in the disturbed than in the control compartment, but there was no difference on larger scales (16 ha) and estimators of true species richness were higher in control than disturbed. Species composition of understorey birds was similar between control and disturbed (Morisita-Horn =0.80).
16. An interspecific comparison of capture rates of understorey birds was carried out. Habitat preference was expressed as the proportion of captures obtained in the control compartment from all captures obtained in both the control and the disturbed compartment. First, habitat preference was significantly correlated with the size of the geographic range. Species with narrow geographic ranges tended to have a higher proportion of captures in the control compartment than geographically more widespread species. Second, there was a significantly positive correlation of habitat preference and body size. Capture rates of larger species (almost only insectivorous passerines) were higher in the control than in the disturbed compartment, the correlation being strong in greenbuls Pycnonotidae. A third feature correlated with habitat specificity was vertical foraging height. Lower foraging species tended to be more specific than those of higher strata.
17. Eight species exhibited significant differences in capture rates between the disturbed and the control compartment. Overall capture rates of understorey birds (all species and all sampling periods combined) did not differ between disturbed and control, but the number of individuals trapped in the disturbed compartment was significantly higher. In one species, the Yellow-whiskered Greenbul Andropadus latirostris, there was a significant proportional difference in the number of individuals captured and the proportion of recaptures between disturbed and control. While the number of individuals captured was higher in the disturbed compartment, the proportion of recaptures in that area was lower. In addition, the mean weight of individuals captured in the disturbed compartment was significantly lower than in those from the control compartment, indicating that there should be a major difference in habitat quality for this species.