The Role of Dispersal in the Great Tit (Parus major): The Causes, Consequences and Heritability of Natal Dispersal

Abstract

Natal dispersal in the great tit in Wytham Wood [England, UK] was examined from data collected during 1964-1975. A large proportion of individuals breed close to where they were born. Females disperse more than males. The median distance of dispersal from birth to 1st breeding site is 558 m for males and 879 m for females. The modal number of territories moved is 1-2 in males and 2-3 in females. Males that are recorded as breeding for the 1st time in their 2nd yr do not disperse further from their natal site than those males known to have bred in the wood in both their 1st and 2nd yr. There are marked annual fluctuations in dispersal in males and females. Dispersal is related to population density in both sexes, negatively with distance in females, positively with the number of territories moved in males. Competition for territories is greater among males than females and eventual natal dispersal may be determined more during the time of territory establishment in the 1st yr of breeding than during the period of post-fledgling dispersal the preceding autumn. Dispersal distance in females is not related to the age or status of their mate. In males, those moving particularly long or short distances are more likely to pair with an older rather than a 1st yr female. Although older females have a higher reproductive success than 1st yr an equivalent advantage to those males at either end of the dispersal distribution was not detected. Absolute dispersal or deviations from median dispersal are not related in either sex to laying date, clutch size or number of fledglings. The probability of predation or desertion is not affected by dispersal. Likewise the rate of mortality within the wood is similar at all distances from the nestbox of birth. The natal dispersal of offspring is similar to that of their parents.