Vertical stratification and seasonal changes of the avian community in Mount Cameroon lowland rainforest
Abstract
While birds are known to show preferences for distinct vertical strata in forests, detailed studies on the vertical distribution of whole communities are still scarce. Furthermore, of those conducted, most have used ground-based methods, including in both tropical and temperate forest.
Here, we utilised ground-to-canopy mist nets to explore the vertical distribution of birds within lowland forest of Mount Cameroon National Park in both dry and wet seasons. In total, 908 birds from 83 species were caught.
Species richness was highest in the understory and decreased towards the canopy as did bird abundance. We sampled more species during the dry season, with some species showing substantial seasonal changes in overall abundance.
No seasonally driven stratal shifts in abundance were observed, while species richness increased in denser strata in the wet season. Although frugivoro-insectivorous birds represented the most species-rich foraging guild, their total abundance was unrelated to height above the ground, season and vegetation cover.
This was also applied to gleaning insectivores, the second most species-rich foraging guild. Omnivores, insectivoro-nectarivores, sallying insectivores and frugivores typically showed a preference for higher vertical strata, while ground-foraging insectivores preferred low forest strata with dense vegetation.
Seasonal variation was most profound in frugivores and sallying insectivores.