Data from: Survival costs of within‐ and between‐season mate change in the European Blackbird (Turdus merula)

Many studies of socially monogamous birds discuss the adaptive role of
between-season partner change, but only a handful of them refer to the
benefits of pair fidelity in terms of increased survival. Moreover, there
are no studies describing the benefits of within-season mate retention.
Our data relating to an urban population of European Blackbirds (Turdus
merula) enabled us to test the dependence of survival on pair
faithfulness. Because Blackbirds divorce within and between seasons, we
were able to test the influence of pair faithfulness on their within- and
between-season survival and mate fidelity. For this purpose, we used a
multievent capture-mark-recapture (MECMR) statistical model, which is
based on recapture rates and different pair states (faithful to mate,
paired with new partner, or dead). Our study indicated that between- and
within-season survival depends on pair states: pair-bond duration
increases survival to the next capture occasion in both sexes. We found
that the pair-bond duration to the current partner increased the chances
of being with the same partner during the next breeding occasion, although
we failed to find any within-season pair-bond influence for females. Our
results showed sex differences in mating at the end of the season: females
had a much smaller chance of breeding with the current new partner in the
next year. This study has demonstrated that within- and between-season
survival is dependent on mate retention, and we discuss this in the
context of how searching for a new partner could affect the birds’
survival.