The relationship between mate guarding and brood desertion in the Rock Sparrow Petronia petronia

Abstract

In several bird species, members of a breeding pair typically face a tradeoff between remating, and consequently deserting the brood, or continuing the original parental effort. The solution of this conflict depends, together with other factors, on the interactions between the paired birds. The Rock Sparrow Petronia petronia is an unusual species in which brood desertion occurs in both sexes and males concurrently engage in parental care and in within- or extrapair sexual behaviours. For these reasons the Rock Sparrow is an excellent species to study the behavioural interactions between pair members in this trade-off context. We studied the sexual behaviour (courtship displays, number of copulations and mate guarding) between pair members before the desertion event in order to obtain a clearer understanding of the process of brood desertion and/or to understand the factors ruling male investment in the current and future reproductive events. In particular, we compared the sexual behaviour of the pair members divided in three groups of pairs: females that cooperate with males (Biparental nests); males that deserted the brood (Female-only nests) and females that deserted (Male-only nests). During the female's fertile period, males that will desert the brood guarded and courted their females significantly more than other males. Moreover, during the young's care phase, males guarded their deserting females more than other males. These results indicate that pair member interactions are important in the desertion process, as assumed by recent theoretical models. This is one of the few studies to show the importance of mate guarding in the brood desertion process.