Willow flycatcher nest success, habitat characteristics, and brood parasitism in southeastern Oklahoma

Abstract

Little is known about Willow Flycatcher (Empidonax traillii) nest success in Oklahoma. In 2009-2010, we opportunistically searched for and monitored Willow Flycatcher nests at Red Slough Wildlife Management Area in McCurtain County, Oklahoma. We also recorded brood parasitism and cause-specific nest loss. We recorded habitat characteristics at each nest site. We monitored one nest in 2009 and 7 nests in 2010. Mean Willow Flycatcher clutch size was 2.7 eggs (range 1-4). Brown-headed Cowbirds (Molothrus ater) parasitized 87.5% of Willow Flycatcher nests with a mean of 1.3 cowbird eggs/nest (range 103). The only un-parasitized nest fledged two Willow Flycatcher. Four nests fledged only cowbirds and three nests were lost to predation. Willow Flycatcher nested in mature sweetgum trees within 5 m of habitat edges. Nest sites were characterized by moderate canopy cover (58%), dense to moderately dense understory vegetation composed of grasses and forbs, and canopy height <12 m. We speculate that Red Slough Wildlife Management Area is a population sink with low Willow Flycatcher nest success due to cowbird parasitism and predation.