Geographical Variation in Egg Mass and Egg Content in a Passerine Bird

Reproductive, phenotypic and life-history traits in many animal and plant taxa show geographic variation, indicating spatial variation in selection regimes. Maternal deposition to avian eggs, such as hormones, antibodies and antioxidants, critically affect development of the offspring, with long-lasting effects on the phenotype and fitness. Little is however known about large-scale geographical patterns of variation in maternal deposition to eggs. We studied geographical variation in egg components of a passerine bird, the pied flycatcher (Ficedula hypoleuca), by collecting samples from 16 populations and measuring egg and yolk mass, albumen lysozyme activity, yolk immunoglobulins, yolk androgens and yolk total carotenoids. We found significant variation among populations in most egg components, but ca. 90% of the variation was among individuals within populations. Population however explained 40% of the variation in carotenoid levels. In contrast to our hypothesis, we found geographical trends only in carotenoids, but not in any of the other egg components. Our results thus suggest high within-population variation and leave little scope for local adaptation and genetic differentiation in deposition of different egg components. The role of these maternally-derived resources in evolutionary change should be further investigated.Peer reviewe

Variation in clutch size in relation to nest size in birds

Peer reviewe

Effects of urbanization on bird phenology:A continental study of paired urban and rural populations

Urban habitats differ from adjacent natural habitats in terms of disturbance regimes, light, temperature, rainfall, habitat distribution and resource abundance. Meteorological differences advance and prolong the growing season in urban habitats compared to nearby rural areas. In turn, urban bird populations may potentially start singing earlier, and reproduce earlier and more frequently than rural populations. However, this prediction has previously only been tested with data from single species using single spatial replicates from rural and urban sites. Here we provide the first general (paired urban and rural populations of 54 bird species) and large-scale (a 3800 km long latitudinal gradient across Europe) empirical evidence for longer and earlier singing periods in urban compared to rural habitats. Effects of urbanization on start and duration of the singing period (as a proxy for the breeding season) were positively related to size of cities and ecological characteristics of species. Bird species that have been urbanized for a long time started to sing earlier and had a more extended singing period in urban compared to rural habitats. We also found that the singing period started later and was shorter at higher latitudes. Geographical variation in phenology was related to temperature and rainfall, although differences between urban and rural habitats were not. Differences in duration of singing periods between paired urban and rural sites were as large as latitudinal differences between southern and northern Europe (5, 6 and 28 d for 3 common species, as compared to a mean latitudinal variation of 17.1 d). This suggests local adjustment to urban environments, either due to evolution or to plasticity of phenological behaviour