Tied to the nest: male black-capped chickadees decrease dawn chorus movement behaviour when their mate is fertile

Male songbirds typically mate-guard by closely following the female during her fertile period. At dawn, males may sing near the nest or roost to direct their chorus at mates. Recent evidence suggests males may also be involved in singing interactions with neighbours during the dawn chorus. We used a 16-channel acoustic location system to examine the movement behaviour of 37 male black-capped chickadees, Poecile atricapillus, during the dawn chorus to determine if male proximity to the nest is a function of breeding stage. Males with fertile females covered a significantly smaller area within their territory, made fewer long-distance movements and sang at a lower song rate compared to males with nonfertile females. Males with fertile mates remained significantly closer to their nest cavity than males with incubating mates. Males with nonfertile mates spent more time near their neighbours with fertile mates than near their neighbours with nonfertile mates. Neither social rank nor age had a significant effect on movement behaviour or song rate. Our results clearly show that female fertility influences dawn chorusing behaviour in male black-capped chickadees. Males may remain near their nest to minimize the risk of cuckoldry, but when their partner is not fertile males may increase movement behaviour to interact with neighbours and/or to advertise to potential extrapair mates.