Data from: Postnatal dispersal and drivers of successful recruitment in resident Poecile gambeli(Mountain Chickadee)

Many animals disperse from their natal sites as juveniles to settle in new
locations where they may eventually breed. Estimating distances of such
postnatal dispersal within and across populations, as well as identifying
factors affecting recruitment success, is important for understanding
evolutionary consequences of dispersal. We investigated patterns of
postnatal dispersal and identified predictors of successful recruitment in
highly resident Mountain Chickadees (Poecile gambeli) using data on 326
recruits of 5,226 total fledglings detected at winter feeders (recruitment
into winter flocks) and nest boxes (recruitment into the breeding
population) over 12 years at two elevational sites in the northern Sierra
Nevada, USA. Like most Parids, chickadees dispersed close to their natal
sites (median distance 644m). Dispersal distance was not associated with
fledgling mass, but females dispersed significantly longer distances than
males. When only considering dispersal distances based on recaptures at
nest boxes, birds that fledged earlier dispersed significantly shorter
distances. Successful recruitment both into winter flocks and into the
breeding population was associated with higher fledgling mass and earlier
fledging. Over the study period, only 13 birds were detected dispersing
from one elevational site to the other, and 12 of these birds hatched at
low elevation and dispersed to the high elevation site. Our results
suggest that earlier fledging timing and higher fledgling mass are both
critical for successful recruitment in Mountain Chickadees. Chickadees
that fledge earlier tend to disperse and breed closer to their natal
sites. Our results confirm that fledgling mass is a key measure of
individual quality in which even small differences in mass (~2-3%) may
have important implications for recruitment, and therefore fitness.