Go your own way? Reasons for divorce in a monogamous seabird

Pair bond duration is usually associated with reproductive success in long-lived monogamous species, yet pairs sometimes divorce. Possible explanations for divorce include having access to a higher-quality partner or territory, selecting a more compatible partner, asynchronous arrival at the breeding site or displacement of one member of a pair by an intruder. Factors influencing the occurrence of divorce are still unknown for many bird species, although divorce is often associated with low reproductive success in the preceding year. The thick-billed murre, Uria lomvia, is a colonial long-lived seabird species that has biparental care and undergoes occasional divorce. In this study, we investigated factors influencing the occurrence of divorce as well as the impact of divorce on subsequent reproductive success using data collected over 24 years at a breeding colony on Coats Island (Nunavut, Canada). Yearly divorce rate averaged 9%. The probability of divorce decreased with breeding experience/age, nest site quality and successful fledging in the previous year. Both sexes initiated divorce. Divorced birds did not obtain a better partner or improve their nesting site quality. Divorce seemed to be triggered by low reproductive success rather than a new partner or nesting site opportunity. Finally, an initial reduction of reproductive success was found for birds that divorced. Our findings help to understand the triggers and consequences of mate changes in long-lived monogamous species. & COPY; 2023 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.