Food niche differentiation in two syntopic sunbird species: a case study from the Cameroon Mountains
Abstrakt
Closely related bird species can coexist in areas of range overlap due to differentiation of their ecological niches. If coexisting species have similar habitat requirements, separation of food niches presumably plays a crucial role.
Theoretically, two possible food niche separation scenarios are possible: (1) use of different food resources or (2) temporal differences in feeding activity. We examined these mechanisms by investigating the feeding habits of two short-billed sunbirds (Cinnyris reichenowi and C. bouvieri) coexisting locally in the Bamenda Highlands, NW Cameroon.
Daily feeding activity in both species showed a similar pattern, with two peaks (0800-0900 hours and 1500-1600 hours, respectively) and a prominent decrease in activity between 1100 and 1400 hours. However, the studied species clearly differed in their exploitation of plant resources.
C. bouvieri mostly visited Lobelia columnaris, while C. reichenowi regularly visited three plant species, namely, Hypericum revolutum, Hypoestes aristata and Impatiens sakerana, with the most time spent at the second species. Such resource partitioning was probably caused by interspecific aggressive behaviour, since C. bouvieri actively repelled C. reichenowi from Lobelia columnaris plants, forcing C. reichenowi to feed on other plant species.