Sex-dependent carry-over between winter social associations and breeding proximity in a communally roosting wild parrot

Between-season carry-over in social associations is widely observed and can have important benefits for individuals, ranging from reduced conflict between neighbours to cooperative nest defence. Yet the underlying drivers of social carry-over effects remain unclear, as current research has predominantly focused on species where breeding territories are influenced by individuals' non-breeding spatial distribution, making it challenging to disentangle social and spatial preferences. Sulphur-crested cockatoos (Cacatua galerita) form communal night-roosts with fission-fusion dynamics around the roost site. During spring, breeding individuals split from the roost to occupy nearby tree hollows but remain non-territorial, allowing us to test whether individuals exhibit a preference to breed in proximity to winter social associates. We find that male-but not female-winter social associations are correlated with breeding location; males bred closer to their winter associates, and more socially connected males tended to breed closer to the roost location. Male cockatoos are largely philopatric to their natal roost and exhibit long-lasting foraging associations, preferentially with kin. Our results demonstrate carry-over between these social networks and the fine-scale arrangement of breeding individuals, a pattern likely consistent with an active choice to retain stable, across-context social relationships.