LAUSR

Individuals of many animal species show consistent differences in ecologically relevant behaviours, and these individual-specific behaviours can correlate with each other. In passerines, aggression during nest-site defence is one of those behaviours that have been steadily found to be repeatable within individuals. Furthermore, in several cases, aggression was related to some estimates of reproductive investment. Here, we studied the possibility that behaviour of males toward a male rival predicts the amount of their future parental care. This could be beneficial to the females, because during mate choice, they could use male aggressive behaviour as a cue for parental quality. We performed the study by video recording the nestling feeding activity of male collared flycatchers (Ficedula albicollis) that were assayed for aggression during the courtship period. The level of aggression was not related to feeding rate in males. Feeding rate of males differed between the study years, but it did not correlate with the feeding rate of their mates, neither was it related to the morphological traits of the parents. We may conclude that nest-site defence aggression of males does not predict their parental commitment. This may be surprising given that higher testosterone levels that may be expected in aggressive males often suppress parental care. However, among-individual variance in male testosterone profiles found to be decrease from the courtship to the parenting period in flycatchers, and this may explain why differences in territorial aggression did not manifest in differences in nestling provisioning. The correlation between behaviours that are expressed in distinct periods of the annual cycle of songbirds needs further investigation.Significance statementMale songbirds, when attracting mates, are often confronted with each other over nest-sites, and these male-male confrontations may be witnessed by females. If performance during territory defence predicts the quality of parental care that a male will provide for its nestlings, females could use defence behaviour as a cue for mate choice. To explore this possibility, we investigated the relationship between territorial aggression and nestling feeding activity of male collared flycatchers. We performed simulated territorial intrusions to measure the aggression of males and recorded their nestling feeding rate about a month later. We found that territorial aggression did not correlate with nestling feeding rate. This suggests that nest-site defence behaviour in the beginning of the breeding season does not carry information for females about what to expect from potential mates in terms of parental care.