Data from: Mate fidelity improves survival and breeding propensity of a long-lived bird

1. Evolutionary and behavioral ecologists have long been interested in
factors shaping the variation in mating behavior observed in
nature.  Whereas, much of the research on this topic has focused
on the consequences of mate choice and mate change on annual reproductive
success, studies of a potential positive link between mate fidelity and
adult demographic rates have been comparatively rare.  This is
particularly true for long-lived birds with multi-year, socially
monogamous pair bonds. 2. We used a 26-year capture-mark-recapture dataset
of 3,330 black brent (Branta bernicla nigricans) to test whether breeding
with a familiar mate improved future breeding propensity and survival. We
predicted that experienced breeders nesting with a new partner would have
rates of survival similar to familiar pairs because long-lived species
avoid jeopardizing survival since their lifetime fitness is sensitive to
this vital rate.  In contrast, we expected that any costs of
breeding with a new partner would be paid through skipping the subsequent
breeding attempt. 3. We found that unfamiliar pairs had lower subsequent
breeding propensity than faithful partners.  However, contrary to
our expectations, individuals breeding with a new mate also suffered
reduced survival. 4. These results add to a small number of studies
indicating that a positive relationship between mate retention and adult
demographic rates may exist in a diverse array of avian species. 
Given these results, researchers should consider costs of mate change that
extend beyond within-season reproductive success to fully understand the
potential adaptive basis for perennial social monogamy.  We
caution that if mate retention enhances survival prospects, improvements
in annual reproductive success with pair-bond length could be a secondary
factor favoring perennial social monogamy, particularly in species with
slower life history strategies.  Further, cases where annual
reproductive success does not improve with pair-bond duration, yet
multi-year pair bonds are common, could be explained by benefits afforded
by mate fidelity to adult vital rates.