Biodiversity, ecology and morphological conformation of forest birds in Southern Benin
LOUGBEGNON O. Toussaint (2008)
PhD, University of Abomey-Calavi
Forest bird communities in Southern Benin was studied in order to compare their biodiversity and their distribution in relation with habitat. Censuses were done in 6 characteristic islets of this part of Benin: Lama forest, Lokoli forest, Niaouli forest, Pobè forest, Ahozon (Pahou) forest and vestigial islet of Dangbo. The objective was to measure the biodiversity and the impact of deforestation on the avifauna in these 6 forest shreds.
Studies were carried out from 2003 to 2007 in 20 stations in these different forests islets. Census method of birds was based on points count of 20 minutes and captures– ringing-recaptures. Different tools and methods of ecological communities analyses such as correspondence analysis and classification hierarchic ascending of Ward, diversity and heterogeneity index, tests of communities comparison (Jaccard, Sorensen), parametric tests (Student, Bartlett and Levene) and no-parametric (Kruskal-Wallis) were used to compare these communities of forest birds.
182 birds species belonging to 46 families were counted in these 6 shreds of forest with a strong representation of passerine birds (93 species) either 51.09 %. But all shreds didn’t have the same bird specifics richness. Birds detectability was very weak in sampled forests. It was even weaker in dense forests that in stations near of borders. The mean diversity index per forest was of 5.87 bits for Lama, 5.67 for Lokoli, 5.60 for Niaouli, 5.18 for Pobè and 4.87 for Pahou; showing sign of a stability of these different forests.
Regularity average was respectively 0.89 of Lama, Niaouli and Pobè forests, 0.88 in Lokoli forest and 0.85 in Pahou forest. IndVals values revealed eight species which were indicatory birds of forest borders against three indicative species of forest inside. Birds distribution between shreds of forest revealed 5 groups of avifauna: avifauna of Lama forest composed of forest species and savannah species, group of upland Niaouli forests incidentally birds of forest border species common to all shreds, indicative avifauna of Lokoli swampy forest, association of birds species occurrence irregular of a forest shred to other and a complex group of characteristic species of Niaouli lowland forest, Pobè forest and birds really ubiquitous to all forests.
Trophic structuring showes that the insectivores dominated extensively in all forest islets: 102 species to Lama, 86 species in Lokoli, 82 species in Niaouli, 63 species to Pobè and 55 species in Pahou. A very meaningful interrelationship existed between predators richness and species richness birds (r = 0.951; p = 0.003). Vertical space distribution of forest avifauna showed that two strata were well provided; these were the herbaceous or bushy stratum extensively represented with 93 species (51.95 %) and canopy 69 species (38.54 %). Interrelationships avifauna-habitat studies revealed a meaningful interrelationship on the one hand between birds species richness and area of forests sampled (r2 = 0.82; p = 0.033) translating that surface reduction of shreds was an inertia to birds biodiversity conservation. Besides, on stations level, only total species richness (S) of stations and diversity (H’) were meaningfully correlated with respectively small woods number, dead woods number and height of vegetation.
Principal Component Analysis of body measurement data done on birds permited to distinguish some species in 5 homogeneous classes: class 1 is for middle size species, class 2 for small size species, class 3 includes relatively big conformation species on other hand, but with a medium beak length, class 4 was a class of medium conformation species but of important beak length and class 5 was of very big conformation species. Southern Benin avifauna was composed of species general practitioners of the Guineo – Congolese block and didn’t present any endemic species. It is also influenced by Dahomey Gap effect. Thirty two species of forest species birds inventoried (either 17.87 %) were threatened to extinctions.
Key words: Birds, forest, biodiversity, ecology, southern Benin.