In seasonal environments, the main selection pressure on the timing of reproduction (the
ultimate factor) is synchrony between offspring requirements and food availability. However, …

1. We investigated the relation between the timing of great tit breeding, measured as the mean
date of laying the first egg in each clutch, the timing of caterpillar availability, measured as …

Understanding the capacity of natural populations to adapt to their local environment is a
central topic in evolutionary biology. Phenotypic differences between populations may have a …

Evolutionary change requires natural selection in the presence of heritable variation for the
trait(s) under selection. Since heritabilities and selection pressures are known to vary with …

During the long-term population study of the Great Tit, all nestlings were ringed and most
parents were identified. This allows the construction of family-trees. In an island population of …

Individual birds of many species laying earlier than the population average produce more
offspring which survive to enter the subsequent breeding population. A shortage of resources …

About 40% of the population variation in the initiation dates of first clutches within years is
genetically determined. The onset of laying, which is determined by the female, is not …

We use data from a long-term population study in combination with DNA fingerprint data to
study the frequency of inbreeding and its effects on reproductive parameters in a blue tit …

We have analysed data on weight and tarsus length collected during a long-term study of
natural populations of Great Tits to evaluate the relative importance of genetic variation in body …

Evolutionary change results from selection acting on genetic variation. For migration to be
successful, many different aspects of an animal’s physiology and behaviour need to function …