Partner retention as a mechanism to reduce sexual conflict over care in a seabird

The costs of caring for offspring are predicted to lead to an evolutionary conflict between parents, where each parent benefits if the other provides the majority of care. However, in many biparental species, breeding partners remain together for multiple breeding attempts and their respective future reproductive fitness prospects are therefore intertwined. Since an increase in current care by a long-term partner reduces that partner’s future investment and longevity, individuals do not automatically only benefit when their partner provides care. We test whether selection will favour individuals that reduce the burden of care falling on long-term partners, thus decreasing evolutionary conflict over parental care. Using a semi-natural, captive colony of black-headed gulls (Chroicocephalus ridibundus), we show that benefits of long-term partner retention can indeed reduce sexual conflict. Long-term partners have less intense courtships and are more behaviourally compatible, and individual..., , , # Title of Dataset: Partner retention as a mechanism to reduce sexual conflict over care in a seabird Set of csv files with data used to perform all analyses described in the paper. ## Description of the Data and file structure Each file is linked to one of the 5 hypotheses described in the paper. These data were used for principal component analysis and data derived from there were used in models to test our hypotheses. Below the variables used in each of the 5 analyses is described in detail: **File 1: Courtship PCA** PairID: unique identifier for the breeding pair DisplayRate: courtship displays per hour JulianDateFirstCourtship: Number of days between the first courtship observation in the colony was observed and the onset of focal pair's courtship JulianLayDate: Number of days between 1st April and the date female laid first egg DaysCourtLay: number of days between first courtship of a pair and first egg lay date PairBondDuration: number of years focal pair had breed together a...