|
Inter-year Distance Between Nest Sites
of Wood Thrush with Respect to
Age, Sex, Previous Year's Success and Mate's Age
Isis Johnson, Courtney Howland, Dan Nelson, Jared Judy, and Roland
Roth
Department of Entomology and Applied Ecology
The successful fledging of avian young depends, in part, on territory
location and placement of nests within the territory. Thus, natural selection
should favor adults that return to sites where they were successful in
the previous year yet avoid previously used but less successful sites.
Age and sex may also influence this site faithfulness. We are examining
these hypotheses with the Wood Thrush (Hylocichla mustelina) population
in the University of Delaware Woods by testing pertinent independent variables
as predictors of the distance between the first nest of a returning bird
in Year X +1 and its first nest in the previous year X, our measure of
site fidelity. During Summer 2002 we located nests, monitored them to determine
the uniquely color-banded owners (and returnees) and their success, and
mapped their locations. Similarly collected data from 2001 gave us the
age, sex, mate age, and success (2 measures) of each returnee and allowed
us to determine between-year inter-nest distances (BYD) for their first
nests. Based on studies that used broader definitions of site fidelity,
we predict that males, older birds, birds mated to older birds, and birds
with more success in Year X will have smaller BYDs. After the initial test
with the 9 male and 9 female returnees from 2001, we will use Roth’s data
from 10 other, non-overlapping pairs of years to enlarge our test. |