Causes and Consequences of Natal Dispersal in the Marsh Tit, Parus palustris

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Abstract
(1) Dispersal distance, measured as the number of territories between place of birth and place of first breeding, was analysed within and between sexes in juvenile marsh tits in relation to factors potentially causing variation in dispersal pattern. (2) Dispersal distance of males was positively influenced by both population density and hatching date. (3) In females, dispersal distance were positively related to population density, number of siblings and wing length. Early-hatched females dispersed further than those hatched in the middle of the season. (4) Dispersal distance in females was positively related to the number of recruits among their offspring. Females surviving for more than one breeding season had dispersed further as juveniles than females breeding only once. In males, dispersal distance did not affect survival or breeding success. (5) It is concluded that males are severely affected by the density of already established individuals, and have no time to choose flock ranges according to quality. Thus, males try to become established as soon as possible after independence. Late-hatched males disperse further and less successful at establishing themselves than early-hatched males. (6) Females, especially those hatched early, more easily become established and can afford to monitor several flock ranges and to be selective in their choice of flock range. This selectively results in long dispersal distances for early-hatched females and a high lifetme reproductive success for long dispersers.