American Ornithological Society 2019, Anchorage, AK (awarded Honorable Mention)
Abstract:
Survival and non-breeding habitat selection of Loggerhead Shrikes in agricultural landscapes of Arkansas
Emily R. Donahue, Lee C. Bryant, Jacob L. Wessels, Joseph Youtz, Rhett Raibley, Alexander J. Worm, Kevin J. Krajcir, Amy A. Chabot, Keith A. Hobson, and Than J. Boves
As intensive agriculture has transformed much of the landscape across central North America, many grassland birds have either disappeared from or declined in these new, highly homogeneous habitats. Despite this conversion, some species, like the Loggerhead Shrike (hereinafter LOSH), still persist in agricultural landscapes. The Lower Mississippi Alluvial Valley (LMAV) is dominated by intensive agriculture but still provides non-breeding habitat for likely co-occurring subspecies (one sedentary, Lanius ludovicianus ludovicianus, and one migratory, Lanius ludovicianus migrans). However, we lack information on the sustainability of these populations, and LOSH non-breeding ecology is understudied range-wide. Specifically, little is known about survival, site fidelity, habitat selection, and if these metrics differ between subspecies during this period of co-existence. To fill these gaps, we banded and monitored 72 LOSH in the LMAV of Arkansas (across 3800 square km) from 2016–2018. We used isotopic (δ2H) and genetic analyses to assign individuals to subspecies and assessed apparent survival, movements, and habitat selection patterns (with a focus on agricultural features). For individuals from both subspecies, we estimated apparent annual survival at 42% and, of those that returned once, 44% survived (apparent) until the third year. Site fidelity was high for returnees; 84% returned to territories within 1 km of their original non-breeding sites. Multiscale analysis of habitat selection revealed availability of perches, in particular utility wires, and presence of agricultural ditches to be preferred features. Our results will assist in the development of improved management and conservation strategies at both local and global scales.
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