Lost opportunities to sire offspring: the cost of parental care in Temminck's stint males

摘要

Losing opportunities for extra matings constitutes an appar-ent price individuals pay when increasing their reproductive success through parental care. This trade-off between parental care and mating effort may depend on several environmental factors. Opportunities for extra matings may also depend on the sex-ratio and on the behaviour of other individuals in the local population. This situation may lead to the emergence of behavioural strategies with regards to breeding decisions. Using the unique breeding system of the Temminck's stint Calidris temminckii we examined the costs of parental care in terms of sired young. This species exclusively shows unipa-rental care, which is performed by either sex. However, both sexes also have the potential for multiple mating and may lose the chance of additional offspring by having parental care duties. Temminck's stint males were classified as incubators (n = 73) or non-incubators (n = 47). DNA samples were col-lected from young and, using molecular parentage methods, the number of sired young was then compared between these groups. Sired young comprised a) total young and b) free young. Free young were defined as young that were incu-bated and cared by another individual. Incubating males were almost twice more likely to sire young than non-incubators. Additionally, incubators sired significantly more young; on average one extra young per year. In contrast, when comparing sired free young, non-incubators were far more likely than incubators to sire free young. Non-incubating males also sired significantly more free young than incubators. Our results suggest that incubators are overall more successful under current conditions. However, incubators could suffer long-term costs due to parental care. Non-incubators sire far more free young, so gain reproductive success without the costs of care. We further explore population conditions that contribute to variation in the relative success of incubating and non-incubating males.