Genotypes selected for early and late avian lay date differ in their phenotype, but not fitness, in the wild

Global warming has shifted phenological traits in many species, but whether species are able to track further increasing temperatures depends on the fitness consequences of additional shifts in phenological traits. To test this, we measured phenology and fitness of great tits (Parus major) with genotypes for extremely early and late egg lay dates, obtained from a genomic selection experiment. Females with early genotypes advanced lay dates relative to females with late genotypes, but not relative to nonselected females. Females with early and late genotypes did not differ in the number of fledglings produced, in line with the weak effect of lay date on the number of fledglings produced by nonselected females in the years of the experiment. Our study is the first application of genomic selection in the wild and led to an asymmetric phenotypic response that indicates the presence of constraints toward early, but not late, lay dates

Managing time in a changing world: Timing of avian annual cycle stages under climate change

Animals need to time their seasonal activities such as breeding and migration to occur at the right time. They use cues from the environment to predict changes and organise their activities accordingly. What happens, then, when climate change interferes with this ability to make predictions? Climate change advances the timing of annual cycle stages, but these shifts may vary among stages. This could interfere with the ability of organisms to organise their entire annual cycle as it modifies the time available for each stage. We investigated the causes and consequences of unequal shifts in the timing of annual cycle stages of the European pied flycatcher (Ficedula hypoleuca). These birds perform a long distance migration from western Africa (where they winter) to Europe (where they breed) and back, staying less than five months in Europe. In this interval, they must fit the important breeding and moult stages, as well as the transition between arriving and breeding and the preparation for the next migration. Timing of arrival breeding and moult changed at different rates in response to climate change, this resulted in a shorter time between arrival and breeding and breeding and moult. Thus climate change has the effect of relaxing time pressures in some cases while tightening it in others. The costs of these shifts, however, varied according to the sex or life stage of the animal. Therefore, for a broader understanding of the ecological consequences of climate change, different stages of the annual cycle should be considered, in particular for organisms with complex cycles

Ingrained city rhythms: flexible activity timing but more persistent circadian pace in urban birds

Urbanization dramatically increases the amount of light at night which may disrupt avian circadian organization. We measured activity patterns of great tits breeding in the city and forest, and subsequently measured two clock properties of these birds under controlled conditions: tau (endogenous circadian clock speed) and after-effects (history-dependency of the clock relative to previous conditions). City and forest birds showed a high repeatability of activity onset (0.60 and 0.41, respectively), with no difference between habitats after controlling for date effects. Activity duration and offset showed more variance, without a difference between birds from the two habitats. Tau did not differ between city and forest birds, however, city birds showed stronger after-effects, taking more days to revert to their endogenous circadian period. Finally, onset of activity was correlated with clocks speed in both habitats. Our results suggest that potential differences in activity timing of city birds is not caused by different clock speeds, but by a direct response to light. Persistence in after-effects suggests a reduced sensitivity of the clock to light at night. Urbanization may select for clock properties that increase the inertia of the endogenous circadian system to improve accuracy of activity rhythms when exposed to noisier lighting cues