Nesting strategy and the niche partitioning in two socially monogamous songbirds

Niche partitioning is often vital for the coexistence of ecologically similar species under limited resources. Here I will report the nesting strategy of the two sympatric songbirds and the species differences, which have been overlooked in the past. Blue-capped and red-cheeked cordon-bleus are socially monogamous, biparental songbirds (family Estrildidae) that sympatrically inhabit East Africa. My field observation during their breeding season revealed that red-cheeked cordon-bleus build their nests near wasp nests more frequently than blue-capped cordon-bleus. Blue-capped cordon-bleus instead tended to take over weaver’s old nest more often or use a broader range of nesting materials compared to red-cheeked cordon-bleus. These nesting strategies are already described in the literature as common behaviors in both species. However, the species differences of the adopting strategies have never been reported. While Estrildid finches are one of the best well-studied bird families of their behavior under the captive condition, my finding suggests that we still have limited knowledge of their wild behaviors and ecological plausibility, which is required to understand the functions and evolution.