The Kirtland's Warbler full annual cycle
This project was part of my research program as a postdoctoral researcher at the Smithsonian Migratory Bird Center and was funded by the US Fish and Wildlife Service. The Kirtland's Warbler (Setophaga kirtlandii) is North America's rarest migratory songbird. Although past research has successfully informed breeding-season recovery plans, both state and regional agencies have identified several other periods of the annual cycle that are in critical need of research. More specifiically, key information is needed regarding: 1) post-breeding survival and habitat use, 2) migration routes, and 3) wintering distributions.
Post-breeding Mortality and Habitat Use
During the post-breeding period fledlging birds are particullarly vulnerable to both predation and starvation. Survival rates during this period range from as low as 22% to as high as 70%. Recent research has shown that fledglings of some species use different habitat types during the post-fledgling period. By attaching radio transmitters to fledglings just before they leave the nest and tracking their survival and movements for ~35 days, I will be able to quantify Kirtland's Warbler's basic survival rates and habitat use for the first time in this species. This past spring (2014), I attached radio-transmitters to 70 fledglings. Analysis of these data is ongoing so check back soon for an update.
Migration Routes, Stopover Sites, and Wintering Locations
Migration routes, and stopover and wintering locations for Kirtland's Warblers are poorly understood. Most annual mortality of adults occurs during migration, but previous research has shown that conditions on the wintering grounds can influece migratory performance. Understanding where and when Kirtland's Warblers migrate represents the necessary first step towards not only better understanding migration and the wintering period, but also conserving habitats crucial for their success.
In May and June of 2014, I attached 60 small (~0.5 g) light-level geolocators to male Kirtland's Warblers throughout their breeding habitat in Michigan. These small devices infer latitude and longitude based on ambient light levels. In 2015, I recovered usable data from 27 devices (see animation to right). We used these data to describe Kirtland’s Warbler migration timing, identify important stopover areas in Ontario, North and South Carolina, Georgia, and Florida. We also discovered that Kirtland’s Warlblers winter in Cuba!. This research was published in the Journal of Avian Biology.
In 2015 and 2016, Joe Wunderle (USFS), Dave Ewert (TNC), and I carried out hundreds of Kirtland’s Warbler surveys on The Abacos and Cat Island in The Bahamas, as well as in Turks and Caicos. We used these data in combination with over a decade of searches carried out by Joe and Dave to refine the wintering distribution and habitat preferences of Kirtland’s Warblers. We determined that the scrub habitats of the central Bahamas are the most important wintering area for this endangered species. This research was published in Endangered Species Research.
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Adult male Kirtland's Warbler with light-level geolocator. The light-sensing stalk is seen extending off of the device that is attached to his back via a leg harness.
Light-level tracking data for 20 male Kirtland’s Warblers for one full year. As colors move from dark to bright, the number of birds overlapping in both time and space increases.