High pair fidelity despite sex differences in the duration of parental care in a long-lived migratory bird

In monogamous birds, pair bond maintenance is often dependent on previous breeding success and each parent’s effort, because partners gain information about one another’s quality and contribution to brood rearing. The asymmetries between mates in parental investment have been theoretically linked to a sexual conflict of interests. Year-to-year pair fidelity decisions in relation to birds’ previous-year information about their mates, including territory quality and relative length of brood care, were explored in red‐necked grebes (Podiceps grisegena), a long-lived species with parent-fed young. Overall, mate retention was a major strategy (81.5% of pair-years). The probability of breakage/maintenance of a pair bond was not affected by previous-year hatching success, fledgling production, or territory quality in terms of food abundance for chicks. Reunited pairs bred earlier in the season than new pairs. In pairs that maintained bonds into the subsequent season, females typically terminated care 1–4 weeks before males. The male fidelity indicates that earlier brood abandonment by females may confer some fitness benefits to males and reflect coordination of reproductive effort at the behavioural level rather than exploitation of one partner by another.