Competition and coexistence of the European Bee‐eater Merops apiaster and the Blue‐cheeked Bee‐eater Merops persicus in Asia

Abstract

Studies were conducted over a 10‐year period on the supposedly similar European Bee‐eater Merops apiaster and Blue‐cheeked Bee‐eater Merops persicus breeding in mixed and separate colonies in four Asiatic countries. In spring, M. persicus arrived a few days later and laid up to 2 weeks later than M. apiaster. Spatial distributions of the two species were positively associated. They were sympatric and syntopic: more than half of the local breeding ranges overlapped, and many birds bred within sight and sound of the congener. Intraspecific conflict was frequent, but in mixed colonies interspecific conflict was rare. Most M. apiaster nest burrows were dug into cliffs and most M. persicus ones into level ground, but dense mixed colonies occurred only in cliffs. Burrow architecture differed specifically. Diets were qualitatively similar at insect family level but different at the species level, partly because of local variation in availability and partly because of distinct preferences of M. apiaster for small beetles, ants and termites and of M. persicus for large dragonflies and cicadas. Merops persicus was less specialized than M. apiaster and had an airborne insect prey spectrum nearly twice as broad. Diets were more alike where the two birds foraged together than where they foraged separately. There was a high incidence of egg and nestling loss by predation and starvation.We speculate that each species may prove to breed more successfully in mixed than in monospecific colonies. We propose that the two bee‐eaters do not compete for nest sites but may compete for food and coexist unaggressively by trading off food competition against improved breeding success in mixed colonies.