Natal dispersal of Great Tits in a patchy environment

The importance of dispersal for population genetics, population dynamics, and conservation biology is well established. We studied natal dispersal of Great Tits between Wytham Wood (high-quality habitat), and hedgerows and small woodlands within 2 km of Wytham Wood (the ''surrounding area''; low-quality habitat). We (1) quantified the exchange of birds between these habitats, and (2) evaluated whether there was phenotypic variation between dispersing and philopatric birds. Only 6% of immigrants in Wytham were born in the surrounding area, and only 5% of emigrant recruits from Wytham bred in the surrounding area. This indicates that most nonphilopatric birds dispersed >2 km, considerably farther than expected. The effect of sex on dispersal depends on the scale on which it is studied: females dispersed longer distances than males, but the exchange of birds between woodlands was not sex biased. The proportion of immigrants among breeding birds was similar for both sexes, confirming the latter result. Dispersing and philopatric birds did not differ in hatch date, but birds that hatched in the surrounding area and dispersed into Wytham had greater nestling mass than those that did not. This effect was not found in Wytham, suggesting that there is an interaction between phenotypic quality and habitat quality with respect to dispersal: birds of high phenotypic quality disperse when they are born in low-quality habitat. As a result, birds breeding in Wytham (high-quality) had greater mass as nestlings than birds breeding in the surrounding area (low-quality). To our knowledge, this is the first demonstration that conditions during early development have an affect on the quality of the environment in which a bird subsequently reproduces.