INCOMPLETE FEMALE KNOWLEDGE OF MALE QUALITY MAY EXPLAIN VARIATION IN EXTRA-PAIR PATERNITY IN BIRDS

We present rind discuss an hypothesis to explain inter- and intraspeci fic Variation in levels of extra-pair paternity (EPP) in birds. In spe cies with biparental care, females may be willing to engage in extra-p air copulation (EPC) to improve the genetic quality of the offspring. However, it may be costly to sample males and difficult to assess thei r genetic quality. Hence, we suggest that variation occurs in the exte nt of such knowledge between females, causing variation in the extent to which they are willing to engage in EPC. From the hypothesis we pre sent nine predictions on occurrence of EPP in birds, e.g. cuckolders s hould mainly be resident, close neighbours; rate of EPP should be posi tively related to breeding density, to rate of male intrusion, to fema le opportunity to assess male quality from competitive interactions be tween males, to early arrival time of females relative to time of egg laying, and to breeding synchrony. Finally, we discuss implications on male behaviour. We suggest a new function of male mate guarding, name ly that mate guarding is a means to prevent the social mate from obtai ning essential information about the quality of potential extra-pair m ates.