Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long-term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement.

The pied flycatcher is one of the most phenotypically variable bird species in Europe. The geographic variation in phenotypes has often been attributed to spatial variation in selection regimes that is associated with the presence or absence of the congeneric collared flycatcher. Spatial variation in phenotypes could however also be generated by spatially restricted gene flow and genetic drift. We examined the genetic population structure of pied flycatchers across the breeding range and applied the phenotypic Q(ST) (P(ST))-F(ST) approach to detect indirect signals of divergent selection on dorsal plumage colouration in pied flycatcher males. Allelic frequencies at neutral markers were found to significantly differ among populations breeding in central and southern Europe whereas northerly breeding pied flycatchers were found to be one apparently panmictic group of individuals. Pairwise differences between phenotypic (P(ST)) and neutral genetic distances (F(ST)) were positively correlated after removing the most differentiated Spanish and Swiss populations from the analysis, suggesting that genetic drift may have contributed to the observed phenotypic differentiation in some parts of the pied flycatcher breeding range. Differentiation in dorsal plumage colouration however greatly exceeded that observed at neutral genetic markers, which indicates that the observed pattern of phenotypic differentiation is unlikely to be solely maintained by restricted gene flow and genetic drift.

R. 2003. Female colour polymorphism covaries with reproductive strategies in the tawny owl Strix aluco. -J. Avian Biol. 34: 393-401.Variation in coloration with a strong underlying genetic basis is frequently found in birds, insects, anurans, molluscs and plants. Although such a variation can be large, little is known about its functional value. Correlative data, however, can help suggest testable hypotheses about potential covariation between reproductive parameters and a colour polymorphism displayed by individuals belonging to a single population. In this context, we studied two Swiss populations of tawny owls Strix aluco, a polymorphic species that varies in coloration from reddish-brown to grey. Observations in the first population showed that although greyer females had shorter tarsi, they produced heavier offspring in two of three years. Pairing with respect to plumage coloration was not significantly disassortative, indicating that these correlations were probably not inflated by plumage coloration of the mate. In the second population, where breeding females had been monitored for 14 years, the proportion of all breeding females that were reddish-brown was greater in years when the breeding density was lower. Capture-recapture analyses show that the latter result is explained by the fact that greyish females bred less often than reddish-brown females, although their survival probability was similar. The number of greyer breeding females was greater when spring/summer temperatures were lower. When combined, the results from the two populations lend support to the hypothesis that grey females do not breed every year, but produce offspring of higher quality. Whatever the mechanism underlying the correlations reported in this study, colour polymorphism in female tawny owls appears to reflect some components of individual quality.A. Roulin (correspondence),

When climatic conditions change and become outside the range experienced in the past, species may show life‐history innovations allowing them to adapt in new ways. We report such an innovation for pied flycatchers Ficedula hypoleuca. Decades of breeding biological studies on pied flycatchers have rarely reported multiple breeding in this long‐distance migrant. In two populations, we found 12 recent incidents of females with second broods, all produced by extremely early laying females in warm springs. As such early first broods are a recent phenomenon, because laying dates have gradually advanced over time, this innovation now allows individual females to enhance their reproductive success considerably. If laying dates continue advancing, potentially more females may become multiple breeders and selection for early (and multiple) breeding phenotypes increases, which may accelerate adaptation to climatic change.

Age-related variation in reproductive performance is central for the understanding of population dynamics and evolutionary processes. Our understanding of age trajectories in vital rates has long been limited by the lack of distinction between patterns occurring within- and among-individuals, and by the lack of comparative studies of age trajectories among traits. Thus, it is poorly understood how sets of demographic traits change within individuals according to their age. Based on 40 years of monitoring, we investigated age-related variation in five reproductive traits in female pied flycatchers (Ficedula hypoleuca) including laying date, clutch size, brood size, nest success (probability that a nest produces at least one chick) and egg success of successful nests (proportion of eggs resulting in a chick). We disentangled within- from among-individual processes and assessed the relative contribution of within-individual age-specific changes and selective appearance and disappearance. Finally, we compared the aging pattern among these five reproductive traits. We found strong evidence for age-specific performance including both early-life improvement and late-life decline in all reproductive traits but the egg success. Furthermore, the aging patterns varied substantially among reproductive traits both for the age of peak performance and for the rates of early-life improvement and late-life decline. The results show that age trajectories observed at the population level (cross-sectional analysis) may substantially differ from those occurring at the individual level and illustrate the complexity of variation in aging patterns across traits.