Climate warming induced a stretch of the breeding season and an increase of second clutches in a passerine breeding at its altitudinal limits

The increase in the average air temperature due to global warming has produced an early onset of the reproduction in many migratory birds of the Paleartic region.According to the“mismatch hypothesis”this response can lead to a decrease in the breeding output when the conditions that trigger the departure from the wintering areas do not match the availability of food resources in the breeding ground.We used 653 brooding events registered during the period 1991–2013 to investigate the link between climatic variables and individual breeding performance of a partially migratory passerine,the Rock Sparrow Petronia petronia,breeding at the altitude limit of its distribution.The laying date(LD)of the earliest first clutch was associated with local spring(minimum)temperatures but did not show a significant trend during the period considered.The LD of the latest first clutch had a positive and statistically significant trend,unrelated to local covariates and resulting in a longer breeding season(1.5 days/year).A longer breeding season allowed birds to produce more second clutches,which proportion increased from 0.14 to 0.25.The average breeding success was also positively correlated with the average temperature in July and with the duration of the breeding season.Contrary to expectations,the most important climate-dependent effect was a stretch of the breeding season due to a significant increase of the LD of the latest first-clutches rather than an earlier breeding onset.We show how climate changes act on bird populations through multiple paths and stress the need to assess the link between climatic variables and several aspects of the breeding cycle.

Contrasting size-dependent life history strategies of an insular lizard

In many species with continuous growth,body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective pressures.We developed a deterministic size-dependent integral projection model for 3 insular neighboring lizard populations with contrasting adult body sizes to investigate how size-related selective pressures can influence lizard life-history tactics.For each population,we broke down differences in population growth rates into contributions from size-dependent body growth,survival,and feeundity.A life table response experiment(LTRE)was used to compare the population dynamics of the 3 populations and quantify the contributions of intrinsic demographic coefficients of each population to the population growth rate(z).Perturbation analyses revealed that the largest adults contributed the most to the population growth rate,but this was not true in the population with the smallest adults and size-independent fertility.Although we were not able to identify a single factor responsible for this difference,the combination of the demographic model on a continuous trait coupled with an LTRE analysis revealed how individuals from sister populations of the same species follow different life strategies and showed different compensatory mechanisms among survival,individual body growth,and fertility.Our results indicate that body size can play a contrasting role even in closely-related and closely-spaced populations.