Radio-tracking reveals insight into survival and dynamic habitat selection of fledgling Cerulean Warblers

Abstract

For most bird species, little is known about their ecology and survival between fledging and independence despite the potential for post-fledging survival to be a factor limiting population dynamics. Cerulean Warblers (Setophaga cerulea) are a declining migratory species, and full-life-cycle conservation efforts that include the post-fledging period are warranted to attempt to reverse their decline. To understand movement, habitat selection, and survival, we radio-tracked 20 fledglings throughout the dependent post-fledging period. Broods were split by their parents, typically (88%) left parental breeding territories within 12 days, and survivors moved 2.4 ± 0.7 km (mean ± SE) from their nest within the 28.1 ± 1.8 day tracking period. Fledglings were usually observed in the mid-canopy to upper canopy and selected habitat with greater mid-story cover, less basal area, and areas closer to water bodies, compared to available points, when considering data from the entire post-fledgling period. However, habitat selection varied with fledgling age. Young fledglings (0–2 days post-fledging) selected areas with greater sapling cover and less stand basal area, but as fledglings matured, they selected areas farther from canopy gaps with greater mid-story cover. Compared with nesting habitat selected by parents, fledglings used areas with smaller and more numerous trees, fewer canopy gaps, and greater mid-story cover. Survival of the entire period was 48 ± 14% and most (8/10) mortalities occurred within the first 3 days post-fledging. Evidence indicated eastern chipmunks (Tamias striatus) as the most common predator. Providing or retaining large tracts of forest is recommended to prevent the restriction of post-fledging dispersal, and managing forests to maintain a heterogeneous landscape that includes stands with numerous canopy gaps and dense understory (e.g., shelterwood harvests or late seral stage conditions) as well as stands with a dense mid-story (e.g., younger stands and riparian areas) appears to be important for this life stage.

Cross-scale habitat selection reveals within-stand structural requirements for fledgling Golden-winged Warblers

“…Our findings are consistent with those on fledglings of other species in that we found a strong relationship between probability of use and patches of greater vegetation density. For example, forest birds including Ovenbirds (King et al 2006, Jenkins et al 2017), Wood Thrushes (Anders et al 1998, Lang et al 2002, Worm-eating Warblers (Helmitheros vermivorum) (Vitz and Rodewald 2011), Acadian Flycatchers (Empidonax virescens) (Jenkins et al 2017) and Cerulean Warblers (Setophaga cerulea) (Raybuck et al 2020) have all been associated with areas of dense understory vegetation during the post-fledging period. Our results are most similar to Ovenbirds, Worm-eating Warblers, and Cerulean Warblers, in that fledgling Golden-winged Warblers selected denser vegetation during the dependent post-fledging phase.…”

Song learning by prairie warblers: When, where, and from whom

“…Radio‐tracking studies of other wood warbler species have documented post‐fledging movements that take fledglings more than 1,000 m from the nest within 30 days of fledging. For example, in that time frame, radio‐tracked cerulean warblers ( Setophaga cerulea ) moved to 2.4 ± 0.7 km from the nest (Raybuck, Larkin, Stoleson, & Boves, 2020), golden‐winged warblers (V ermivora chrysoptera ) to 1,238 ± 528 m (Streby, Peterson, Kramer, & Andersen, 2015), worm‐eating warblers ( Helmitheros vermivorum ) to 1,141 ± 245 m (Vitz & Rodewald, 2010), and ovenbirds ( Seiurus aurocapilla ) to 1,314 ± 174 m (Vitz & Rodewald, 2010). If our returning prairie warbler nestlings moved over similar distances, most of them would likely have been exposed to the songs of both of their models (for all six returning nestlings, the first category model and the second category model were different birds).…”

Cerulean Warblers in the Ozark region: habitat selection, breeding biology, survival, and space use

“…We continued resighting efforts for individuals until we either failed to resight them for three consecutive weeks or their young fledged. Fledglings can roam beyond territorial boundaries (Raybuck et al 2020), making males difficult to detect. In 2019 and 2020, we attempted to resight returning banded males to estimate apparent annual survival.…”