Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

Currently there is great debate about whether monogamy and associated kinship is a key element in the evolution of cooperation. Monogamy leads to high levels of kinship when dispersal of young is delayed (allowing kin selection for altruistic behaviour and cooperative breeding). However, delayed dispersal also leads to stable social interactions with known group members (allowing reciprocation of helpful behaviours which may provide direct fitness). Most studies of cooperative breeders focus on monogamous kin-based cooperative groups, thus confounding mating system and cooperation. I study two species in which monogamy and kin-based cooperative breeding are not correlated. The long-term goal of my research program is to determine how kinship, mating system, and social stability within groups affect cooperation and conflict in group breeding birds.

We study two species of communal joint-nesting birds – birds that breed in groups including multiple breeding males and females that collectively lay eggs to produce a joint-clutch in single shared nest. Smooth-billed anis (Crotophaga ani; Cuculidae) live in non-kin groups of monogamous pairs. Pukeko (Porphyrio melanotus melanotus; Rallidae) usually live in close kin groups and breed polygynandrously – multiple male and female breeders mate with each other without pair bonds.

I will address three main questions over the course of this grant. First Question: What are the fitness consequences of communal joint-nesting? In projects 1 and 2 with anis we will examine direct fitness benefits of cooperative breeding in a non-kin parasitic system. In project 3 with pukeko, we will test the hypothesis that the laying of synchronized joint clutches by two female kin improves inclusive fitness compared with extended laying by a dominant female alone.

Second Question: Do individuals favour their descendent young over non-descendent young in communal kin groups, and if so what adaptations underlie such favoritism? In project 4 we will test the hypothesis that female pukeko breeders show maternal favouritism towards their own young even within a kin selected system.

Third Question: How is subordinate female reproduction modulated by dominant females in cooperative breeding species? North Island (New Zealand) populations of pukeko live in stable kin groups on year-round territories and subordinate females show reduced levels of reproduction. In contrast, South Island non-kin groups live in seasonal territories (held part of the year; less stable) and subordinate females do not show reduced levels of reproduction. In project 5 we will use female removal experiments to test the hypothesis that dominant females in stable joint-nesting groups on permanent territories modulate reproduction by subordinates.