Parent-offspring competition and natal dispersal at several spatial scales in the great tit, Parus major

Models predict that condition-dependent dispersal can be promoted by variation in the intensity of kin competition. In particular, natal dispersal should be reduced as the parents' chances of survival decrease with age. The response to parental age should depend on the offspring's sex because of the asymmetry of competition between the sexes. We tested these predictions in the great tit population of Wytham Wood (Oxfordshire) where adult survival was shown to be age-dependent. Natal dispersal within the wood was dependent on the mother's age but not on the father's. Whereas young males were not affected by the mother's age, young females were found to disperse less when their mother was old. This indicates that mother-daughter competition can promote dispersal in the species. The same response was found whatever the spatial scale at which natal dispersal was examine

Effect of wintering area and climate on the survival of adult Atlantic puffins <i>Fratercula arctica</i> in the eastern Atlantic

Despite contrasting population trends ranging from -3 to + 11% per annum, the annual survival rates of Atlantic puffins Fratercula arctica in the 5 colonies spanning the species range in the east Atlantic were virtually identical over a 10 to 15 yr period, giving no support to the hypothesis that variation in population growth rates is driven by adult survival. The extent to which survival varied among years differed markedly between colonies. Similarities between colonies in the patterns of inter-annual variation in survival did not reflect similarities in wintering areas, as indicated by recoveries of ringed birds, nor the geographic proximity of the colonies. However, survival in 4 of the 5 colonies correlated with sea surface temperatures around each colony 2 yr earlier. The relationship between survival and sea temperature was positively correlated with the effects of sea temperature on recruitment of the Atlantic puffin's main prey species, the lesser sandeel Ammodytes marinus, the herring Clupea harengus and the capelin Mallotus villosus

Modelling survival at multi-population scales using mark-recapture data

The demography of vertebrate populations is governed in part by processes operating at large spatial scales that have synchronizing effects on demographic parameters over large geographic areas, and in part, by local processes that generate fluctuations that are independent across populations. We describe a statistical model for the analysis of individual monitoring data at the multi-population scale that allows us to (1) split up temporal variation in survival into two components that account for these two types of processes and (2) evaluate the role of environmental factors in generating these two components. We derive from this model an index of synchrony among populations in the pattern of temporal variation in survival, and we evaluate the extent to which environmental factors contribute to synchronize or desynchronize survival variation among populations. When applied to individual monitoring data from four colonies of the Atlantic Puffin (Fratercula arctica), 67% of between-year variance in adult survival was accounted for by a global spatial-scale component, indicating substantial synchrony among colonies. Local sea surface temperature (SST) accounted for 40% of the global spatial-scale component but also for an equally large fraction of the local-scale component. SST thus acted at the same time as both a synchronizing and a desynchronizing agent. Between-year variation in adult survival not explained by the effect of local SST was as synchronized as total between-year variation, suggesting that other unknown environmental factors acted as synchronizing agents. Our approach, which focuses on demographic mechanisms at the multi-population scale, ideally should be combined with investigations of population size time series in order to characterize thoroughly the processes that underlie patterns of multi-population dynamics and, ultimately, range dynamics

Age-dependent genetic variance in a life-history trait in the mute swan

Genetic variance in characters under natural selection in natural populations determines the way those populations respond to that selection. Whether populations show temporal and/or spatial constancy in patterns of genetic variance and covariance is regularly considered, as this will determine whether selection responses are constant over space and time. Much less often considered is whether characters show differing amounts of genetic variance over the life-history of individuals. Such age-specific variation, if present, has important potential consequences for the force of natural selection and for understanding the causes of variation in quantitative characters. Using data from a long-term study of the mute swan Cygnus olor, we report the partitioning of phenotypic variance in timing of breeding (subject to strong natural selection) into component parts over 12 different age classes. We show that the additive genetic variance and heritability of this trait are strongly age-dependent, with higher additive genetic variance present in young and, particularly, old birds, but little evidence of any genetic variance for birds of intermediate ages. These results demonstrate that age can have a very important influence on the components of variation of characters in natural populations, and consequently that separate age classes cannot be assumed to be equivalent, either with respect to their evolutionary potential or response

Great tits growing old: selective disappearance and the partitioning of senescence to stages within the breeding cycle

Deterioration of reproductive traits with age is observed in an increasing number of species. Although such deterioration is often attributed to reproductive senescence, a within-individual decline in reproductive success with age, few studies on wild animals have focused on direct fitness measures while accounting for selective disappearance and terminal effects, and to our knowledge none have determined how senescence effects arise from underlying reproductive traits. We show for female great tits that such an approach helps understanding of the onset, impact and architecture of senescence. Cross-sectional analysis of 49 years of breeding data shows annual recruit production to decline from 3.5 years of age, this decline affecting 9 per cent of females each year. Longitudinal analyses, however, show that selective disappearance of poor-quality breeders partly masks senescence, which in fact starts at 2.8 years and affects 21 per cent of females each year. There is no evidence for abrupt terminal effects. Analyses of underlying traits show no deterioration in clutch size, but significant declines in brood size and fledgling number. Furthermore, these traits contribute −9, 12 and 39 per cent to the senescent decline in recruit production, respectively. Besides providing detailed knowledge of the patterns and architecture of senescence in a natural population, these results illustrate the importance of modelling individual variation, and facilitate study of the underlying mechanisms of senescence