Frequent Copulations and Mate Guarding as Alternative Paternity Guards in Birds: a Comparative Study

Abstract

Male birds use a number of paternity guards to increase their certainty of paternity. Mate guarding appears to be the primary paternity guard, whereas frequent intra-pair copulations are used when males for ecological reasons are unable to closely guard their mates (e.g. in colonially breeding species where one pair member continuously has to guard the nest site against conspecifics, and in species where males provide their mates with all food during the fertile period). We tested whether mate guarding and frequent copulations are alternative paternity guards in a comparative study of the copulation behaviour of 173 bird species with detailed information available. The data base was reduced to statistically independent observations by calculating contrasts (standardized linear differences) between different taxa for copulation frequency, presence of mate guarding, mating system and body mass. Contrasts in mate guarding were strongly negatively related to contrasts in copulation frequency suggesting that they are alternative strategies. Body mass was unrelated to both of the alternative paternity guards, as revealed by weak negative correlations between contrasts in body mass and contrasts in frequent copulations and mate guarding, respectively. Males of taxa with mating systems with the most extreme skew in mating success (i.e. highly polygynous taxa) were characterised by an absence of both the frequent copulation and the mate guarding paternity guards.