Parental care in relation to paternity in the reed bunting (Emberiza schoeniclus)

This study describes the male and female role in parental care in a Norwegian population of reed buntings (Emberiza schoeniclus). The population has an extensive level of extra-pair young (EPY), with 30% of the offspring and 54% of the nests, but this is lower than in other European populations. Male reed buntings face a trade-off between mating effort, parental effort and somatic effort. The male can follow different alternative strategies related to the amount of extra-pair offspring in the population as a whole, and in his own nest. Depending on male ability or inability to assess the cuckoldry in his nest, he can respond facultatively to the present situation, through a non-facultative evolved optimal behaviour or e.g. because of restrictions by breeding synchrony and his physical condition. We found that during the egg and early nestling stage, males brooded less than females. The male parental care was generally lower than the female care, but higher than in other reed bunting populations. We argue that this might be caused by climatic restrictions in pursuing EPCs at cost of incubation. At a later nestling stage, there were no clear differences in male and female behaviour directed at the offspring (e.g. feeding and brooding), but males spent significantly less time nursing. The higher male effort at the nestling stage might be caused by a lower trade-off to pursuing EPCs at this stage, but the result might have been influenced by several other factors. Considering cuckoldry in the male's nest, we found a negative relation between paternity and male pre- and posthatch brooding. There was a non-significant tendency of a positive relation between paternity and the number of feeds. For this population, we argue that the most likely cause of higher individual male brooding to higher cuckoldry in his nest is a best-of-a-bad-job situation, as a consequence of low male mating success. The tendency of a higher male feeding rate with paternity might be explained by a seasonal weaker trade-off with mating effort, and a high necessity or benefit of biparental feeding. We found evidence of a non-facultative response to paternity, and no evidence of any facultative responses. Further studies are needed to demonstrate the importance of female choice, age, climate and other factors in individual differences of paternity levels and male parental care, and whether there are distinct and heritable strategies according to these