

Type of Document Master's Thesis Author Daniels, Susan J. III Author's Email Address sdaniels@vt.edu URN etd-81197-102711 Title Female Dispersal and Inbreeding in the Red-cockaded Woodpecker Degree Master of Science Department Biology Advisory Committee
Advisor Name Title Jeffrey R. Walters Committee Chair David R. Notter Committee Member Robin M. Andrews Committee Member Keywords
- Picoides borealis
- natal dispersal
- breeding dispersal
- inbreeding depression
- inbreeding avoidance
- optimal inbreeding
- cooperative breeding
Date of Defense 1997-08-25 Availability unrestricted Abstract Dispersal is a critical life-history component; it determines gene flow and hasprofound effects on population structure, demography, social systems, and population
viability. To add to our knowledge of dispersal and, in particular, our understanding of
the relationship between dispersal and inbreeding, I studied three aspects of the biology of
the red-cockaded woodpecker: dispersal of breeding females; the costs, benefits, and
frequency of inbreeding; and the effect of inbreeding on natal dispersal.
Dispersal of breeding female red-cockaded woodpeckers is strongly associated
with inbreeding avoidance and mate choice, weakly associated with site choice, and not
found to be associated with social constraints. Estimates of mortality for non-dispersing
and dispersing breeding females were 24 and 59 percent per year, respectively—rare
evidence of the cost of breeding dispersal.
Significant costs of close inbreeding were found. Closely related pairs (kinship
coefficient greater than 0.1) had lower hatching success as well as lower survival and
recruitment of fledglings than unrelated pairs. Moderately related pairs (kinship
coefficient between 0 and 0.1) and moderately inbred individuals had increased hatching
success, but did not produce more young.
Despite documented costs of close inbreeding and a predictable spatial distribution
of closely related males near the natal territory, female fledglings disperse a median of only
two territories and a modal distance of one territory. Natal dispersal of females is affected
by closely related males on the natal site but unaffected by closely related males or
moderately related males that are off the natal site.
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