Brood desertion in Kentish plover: sex differences in remating opportunities

To understand the evolution of parental care, one needs to estimate the pay offs from providing care for the offspring and the payoffs from terminating care and deserting them. These payoffs are rarely known. In this study we experimentally estimated the rewards from brood desertion in a species that has a variable pattern of parental care. In particular, either the female or the male parent may desert the brood in Kentish plover Charadrius alexan drinus, so some broods are attended by one parent of either sex, whereas in other broods both parents stay with the brood until the chicks fledge. We created single males and single females by experimentally removing the othe r parent and the clutch. The expected remating time of males was significan tly higher (median: 25.4 days) than that of the females (5.3 days, p <.0001 ). The expected remating time tended to increase over the breeding season i n both sexes, although the increase was significant only in females. The ne w nest of remated males was closer to their previous territory (mean +/- SE , 46 +/- 8 m) than that of the remated females (289 +/- 57 m, p <.001). Hat ching success of new nests was not different between remated males and fema les. Our results demonstrate that the remating opportunities are different for male and female Kentish plovers and these opportunities vary over the s eason. We propose that the remating opportunities were influenced by the ma le-biased adult sex ratio and the seasonal decrease in the number of breede rs. However, we stress that measuring remating times is a more direct measu re of mating opportunities than calculating the operational sex ratio.