Abstract
Detailed information spanning the full annual cycle is lacking for most songbird populations. We examined breeding, migration, and non-breeding sites for the Yellow-breasted Chat (Icteria virens, chat). We deployed archival GPS tags and light-level geolocators on breeding chats in British Columbia and light-level geolocators in California from 2013 to 2017 to determine migration routes and non-breeding sites. We examined whether chats overwintered in protected areas and characterized the percent of land cover within 1 km. We used a combination of genetics and stable hydrogen isotopes from feathers collected on non-breeding chats in Nayarit, Mexico (2017–2019) and migrating chats in Chiapas, Mexico (2018) and Veracruz, Mexico (2014–2015) to determine subspecies and infer breeding location. Endangered chats in British Columbia followed the Pacific Flyway and spent the non-breeding period in Sinaloa and Nayarit, Mexico. Two out of five chats spent the non-breeding period in protected areas, and the most common landcover type used was tropical or subtropical broadleaf deciduous forest. We found no mixing of eastern and western chats in our Mexico sites, suggesting strong migratory connectivity at the subspecies level. Western chats likely originating from multiple breeding latitudes spent the non-breeding period in Nayarit. Eastern Yellow-breasted Chats likely breeding across various latitudes migrated through Veracruz and Chiapas. Our results provide precise migration routes and non-breeding locations, and describe habitat cover types for chats, notably an endangered population in British Columbia, which may be valuable for habitat protection and conservation efforts.
Highlights
Most songbird research occurs on the breeding grounds and, large knowledge gaps exist for migration and non-breeding periods (Marra et al 2015, 2019)
BC chats that spent the non-breeding season in western Mexico share this region with other western chats originating from multiple breeding latitudes, likely including those that bred in California
Protecting additional sites in western Mexico that support patches of ongoing early-successional habitat and tropical or subtropical broadleaf deciduous forest will be beneficial to conserving western chats generally, and the endangered population that breeds in BC
Summary
Most songbird research occurs on the breeding grounds and, large knowledge gaps exist for migration and non-breeding periods (Marra et al 2015, 2019). Understanding the full annual cycle is important because threats contributing to declining populations may be greatest during migration or the non-breeding period (Rockwell et al 2017; Wilson et al 2018). Non-breeding habitat quality can influence body condition (Black-throated Blue Warblers, Setophaga caerulescens, Bearhop et al 2004) and arrival to breeding sites (American Redstarts, S. ruticilla, Marra et al 1998; Norris et al 2006; Kirtland’s Warbler, S. kirtlandii, Rockwell et al 2012; Cooper et al 2017), which affects territory access (American Redstarts, Marra et al 1998). Birds returning early have earlier laying dates, larger clutches, and greater reproductive success (American Redstarts Norris et al 2004, Reudink et al 2009; Pied Flycatchers, Ficedula hypoleuca, Goodenough et al 2017, Kirtland's Warbler, Rockwell et al 2012), there can be a trade-off in arriving early to the breeding grounds (Brown and Brown 2000)
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