title: Partners in parenthood: the impact of within-pair dynamics on parental care in long-lived seabirds
Creators: name: McCully, Fionnuala
Publisher: name: University of Liverpool Repository
Year: 2024

description: Biparental care is a cooperative enterprise where two individuals act both independently and in congress to rear their offspring. Historically, literature has focused on the conflicts that may arise between parents. Despite this, for long-lived monogamous species where mated partners share lifetime fitness, cooperation is a more profitable strategy than conflict. In order to work together efficiently, individuals should incorporate information on both their own and their partner’s behaviour into decisions, thereby promoting a complementary parental care strategy between pair members. However, responding appropriately to a partner may incur costs by constraining individual autonomy. It remains unclear whether individual need or within-pair interactions take precedence when determining parental care behaviours, and what the fitness consequences of poor cooperation might be. This thesis focusses on the parental care behaviours of long-lived, monogamous seabirds to explore themes related to the coordination of parental care, sensitivity to partner need and within-pair behavioural compatibility. It discusses how within-pair dynamics impact the parental care behaviour of two species- the black-legged kittiwake (Rissa tridactyla) and the wandering albatross (Diomedea exulans). Using foraging data collected via biologging technology, this thesis describes coordinated parental care (the matching of foraging trip durations) in both these species for the first time. By examining behavioural data alongside records of age, personality and partnership history, the chapters of this thesis aim to shed light on how breeding partners influence one another’s behaviour, explore how intrinsic state impacts willingness to cooperate and discuss mechanisms by which behavioural compatibility might benefit pair fitness and mate retention. Firstly, this thesis demonstrates that kittiwake pair members coordinate trip durations over both a long and short timescale, however it posits that kittiwakes respond to their partner’s more recent behaviour to avoid accruing investment debt. It is also argued that the detection of coordinated care in two breeding stages and a lack of between-pair variation in coordination strength hints at the importance of this behaviour for maintaining equal effort within breeding pairs. Secondly, this thesis shows that that while the trip durations of breeding wandering albatrosses were significantly influenced by their partner’s intrinsic state (for example their personality or age), these interindividual differences did not explain variation in coordination strength between pairs. It is proposed that birds assess their partner’s willingness or capacity for care and then adjust their own foraging strategy accordingly to protect their partner’s condition and minimise the risk of breeding failure. Finally, this thesis reports an indirect effect whereby kittiwake partners with similar personalities have higher breeding success, leading to lower rates of re-pairing. These results allow this thesis to propose a link between cooperative parental behaviours and pair fitness outcomes, and discuss how birds may utilise information on personality and compatibility to facilitate mate retention. Overall, this thesis highlights the importance of cooperative behaviours in parental care and demonstrates that mated partners have notable influence over one another’s decisions. This provides valuable insight into how long-lived monogamous animals divide care and the complexity of their decision-making processes. Furthermore, these findings encourage parental care researchers to view parents as interdependent facets of a single caring unit and avoid considering pair members’ behaviour in isolation. This concept has implications for the study of all animals that share care.