Does nest concealment in Wood Thrushes predict predation risk and female stress levels?
Israel, Alexandra May Alice Helen
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The Wood Thrush (Hylocichla mustelina) is a long-distance migrant that has declined severely in the last 50 years and is currently listed as a Species at Risk in Canada. This study investigated whether nest concealment from nest predators and brood-parasitic Brown-headed Cowbirds had an influence on the success of Wood Thrush nests. Through visual estimates of concealment in 186 nests over 3 years, results show that Wood Thrushes experience high nest predation (53.2%) and moderate cowbird parasitism (25.3%) in southwestern Ontario. However, nest concealment does not predict probability of having a successful nest or evading parasitism. We also tested if nest concealment impacts an incubating females flight initiation distance (FID) or corticosterone level (a measure of stress). Although we found no correlation between these variables, this is the first step in understanding if nest site selection affects the female directly, and not just her immediate nesting success.