Male-Specific Territoriality and Use of Specific Calls during the Non-Breeding Season in the Polygynous Eurasian Wren Troglodytes troglodytes

Territory quality is an important factor that influences male reproductive success, especially for polygynous species, in which only males with high-quality territories that provide sufficient resources for multiple females can achieve polygyny. Because males that establish territories earlier are more likely to obtain territories of higher quality, males of polygynous species are predicted to start territorial competition before the breeding season starts. I investigated the territory formation of a polygynous species, the Eurasian Wren Troglodytes troglodytes during winter at their breeding site in Japan. In this population, breeding sites are typically located in mountainous areas, and wrens are thought to migrate to lowlands in winter. However, I found that many males held winter territories at their breeding site and that most maintained their territories in the subsequent breeding season. In defending winter territories, wrens used specific calls instead of songs. It is possible that, despite the cost of territorial defence during winter, it is a strategy that allows males to secure access to high-quality breeding territories, thereby increasing their reproductive success.