CONFIDENCE OF PATERNITY, ACTUAL PATERNITY AND PARENTAL EFFORT BY PURPLE MARTINS

Parental effort by socially monogamous purple martins was measured to test the hypothesis that males reduce care in response to their risk o f losing paternity through extra-pair copulations. Male martins occur in two age classes, with one-year-old males cuckolded in very high fre quencies and older males achieving nearly complete paternity. This out come is because females paired to young males pursue a mixed mating st rategy of seeking extra-pair copulations, and females paired to old ma les avoid extra-pair copulations. Using multi-locus DNA fingerprinting to determine paternity, nb evidence was found that males reduced effo rt according to actual paternity or presumed confidence of paternity. Young and old males provisioned nestlings at similar rates in relative and absolute terms. There was also no relationship within the young a ge class, with young males provisioning similarly regardless of whethe r they were cuckolded. Young males achieving zero paternity provisione d similarly to young males achieving partial and complete paternity, s uggesting that no threshold effect exists. Although several conditions have been proposed under which no relationship between paternity and male care is expected, these conditions did not exist for purple marti ns. Another condition under which males should not reduce care to unre lated offspring is proposed, namely, that performing poorly in the pre sence of potential future mates or extra-pair copulation partners can lower social status and thereby fitness. The 'status hypothesis' provi des a perspective for viewing parental performance as a behavioural ch aracter on which sexual selection operates. (C) 1996 The Association f or the Study of Animal Behaviour.