In 2012 we repeated our 2011 efforts with a substantial increase in data collected. This
was the second and final full field season investigating population ecology of Golden-winged
Warblers (Vermivora chrysoptera; hereafter GWWA) at Tamarac National Wildlife Refuge
(NWR) and Rice Lake NWR in Minnesota and Sandilands Provincial Forest (PF) in Manitoba.
We assessed nesting habitat use, nest productivity, fledgling survival, and post-fledging habitat
use by GWWA at all three sites. We color banded 107 adult female and 112 adult male GWWA
and we attached radio transmitters to 108 adult females. By tracking radio-marked females and
by nest searching, we found and monitored 149 nesting attempts including 2 nests found by
others conducting research at Tamarac NWR (see acknowledgments). The 66% increase over the
2011 nest sample was partly due to increased effort to radio-mark adult females, but mostly to the
return of many experienced nest searchers from 2010 and 2011. We banded 311 nestlings and
fledglings and radio-tracked 175 fledglings. We collected data on habitat characteristics and
GWWA behavior at >2,400 adult, nest, and fledgling locations. Including renesting, we
estimated that 58%, 74%, and 79% of females successfully nested and that 53%, 49%, and 48%
of fledglings survived to independence from adult care at Tamarac NWR, Rice Lake NWR, and
Sandilands PF, respectively. Interestingly, the increases (over 2011) in successfully nesting
females at Rice Lake NWR and Sandilands PF were accompanied by considerable decreases in
fledged brood size due to many partial-brood nest predation events, and the decrease in
successfully nesting females at Tamarac NWR was accompanied by a considerable increase in
fledged brood size. Similar to 2011, nest failure and fledgling mortality were due nearly entirely
to predation at the Minnesota sites, whereas weather exposure and blowfly infection accounted
for a relatively high percentage (23%) of fledgling mortalities at Sandilands PF. Unlike previous
years, we tracked at least one (total = 6) nestling or young fledgling at each site to a garter snake
(i.e., inside the snake), possibly reflective of the warmer, dryer early spring weather. Consistent
with 2011, 30% of radio-marked females nested in older forest stands traditionally not considered
GWWA habitat, and fledged family groups moved into and spent much of the post-fledging
period in those older forest areas. Early findings from this project have been disseminated in 2
peer reviewed scientific journal articles and 2 more are currently in review. Detailed analyses for
manuscripts about transmitter effects, population dynamics, micro- and macro-scale habitat
associations, nest-site choice, parental care of fledglings, and interesting natural history
observations are all underway.
Streby, Henry M; Peterson, Sean M; Andersen, David E.
DEMOGRAPHIC RESPONSE OF GOLDEN-WINGED WARBLER TO HABITAT MANAGEMNET ACROSS A CLIMATE CHANGE GRADIENT IN THE CORE OF THE SPECIES' RANGE: 2012 SUMMARY REPORT.
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