MATE PROTECTION IN ALPHA PAIRS OF WINTERING WILLOW TITS, PARUS-MONTANUS

Willow tits live within flock territories during the non-breeding season. The flocks are organized into a linear dominance hierarchy, whereby the males generally dominate the females and the adults dominate the juveniles of the same sex. In each of the 14 flocks examined in this study (each consisting of six birds: one adult pair and two juvenile males and two juvenile females), the adult female, the mate of the alpha male, was dominated by all males. However, she was involved in fewer dominance interactions than the other flock members, and allocated more of her time to foraging and less to vigilance compared with the juveniles when her mate was close by (within 5 m) than when he was distant. The increase in foraging by the adult female was not itself significant although the overall change for her and the juveniles was. Despite her lower dominance ranking, the adult female showed approximately the same average daily growth of an induced tail feather (i.e. indicating an equal nutritional status) during the winter as the juvenile males did. It is suggested that, by protecting his mate from dominant flock members and securing access for her to preferred resources, the alpha male might increase the probability of survival of his mate during the winter and is thus able to start breeding early on during the following spring. © 1992 The Association for the Study of Animal Behaviour.