What is the typical sequence of events in Tree Swallow pair formation?
Males must successfully claim a nest cavity first, because females won’t pair with males unless they posses this most vital resource. Males use displays and calls to point their cavity out to passing females. Females that do approach often receive a hostile response from the males at first, the same type of response they would give to repel other males intruding into their space. Females that are really interested must overcome their fear and return repeatedly, giving displays that identify themselves as females and gradually pacify the males. Once the male comes to recognise a particular female as a non-threatening individual and a potential mate his hostility lessens, and the two can begin to use other displays to cement their pair bond.
