Laying Date in the Coot: Effects of Age and Mate Choice

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Laying date in coots advanced with the age of both the male and the female. 2. Individual females had different but rather constant laying dates. After controlling for these differences, the effect of female age on laying date remained, but that of male age disappeared. This implies that both early and late females advanced their laying date when becoming older. It also implies that male age has no direct effect on laying date, but that older males are better able to compete for earlylaying females. 3. Selective loss of late-breeding females from a cohort is a potential additional cause for a correlation between age and laying date. However, female survival rate was independent of laying date, thus refuting the selection hypothesis. 4. The data supported neither increased reproductive effort with age (residual reproductive value hypothesis), nor differential delay of reproduction between early and late females (delayed reproduction hypothesis) as additional explanations for the advancement of laying date with age. This advancement in the individual female is therefore considered to be due to increasing quality (maturation hypothesis). 5. The repeatability of laying date in females was 0-32, but the heritability, estimated with daughter-mother regression, was only 0-02. This indicates that the variation in laying date between individuals is predominantly environmental.

The timing of birds' breeding seasons: a review of experiments that manipulated timing of breeding

“…Such a seasonal trend would by itself predict high-quality parents or those breeding on high-quality territories to breed early, and so translate their phenotypic quality into high reproductive success. Independent evidence for this is the general finding that old individuals breed earlier than young ones (Perdeck & Cavé 1992;Moreno 1998). Older individuals are generally of higher phenotypic quality, either through individual improvement through experience, or through selective disappearance of low-quality individuals It is not necessary to invoke a direct effect of date on reproductive success to predict high-quality birds to breed early, because the fitness benefits for high-quality breeders to reproduce early may be independent of the seasonal decline in reproductive success that is observed.…”

Age-Specific Reproductive Success: Evidence for the Selection Hypothesis

“…Many studies have failed to support the idea that breeding success increases with age due to the disappearance of lowproductivity individuals (Sydeman et al 1991b;Desrochers 1992;Desrochers and Magrath 1993;Wheelwright and Schultz 1994;Robertson and Rendell 2001). Others have found just the opposite, that poor parents (low reproductive success) survive better than highly productive parents (Perdeck and Cave 1992;De Forest and Gaston 1996).…”

Experimental evidence that age-specific reproductive success is independent of environmental effects

“…However, generally, there is also an age-related di¡erence in the timing of breeding associated with the observed di¡erences in breeding success. Younger individuals tend to breed later in the season than older birds and may experience di¡erent environmental conditions as a result (Perdeck & Cave¨1992). Therefore, in correlative studies in which reproductive success is examined in relation to age, the potentially independent e¡ects of the time of year and age are confounded.…”