Intraspecific diversity in post-breeding migration
What shapes diversity in migratory behavior within a species, and how do differences expose them to distinct threats? For mature birds, breeding site can play an important role in shaping the timing, route, and behavior of post-breeding migration. Position of breeding location can push birds to encounter a geographic migratory barrier early in its migration, favorable wind conditions or a region of human-impacted area. As they are less time-constrained, birds conducting post-breeding migrations can exhibit more flexibility and variation than they might during pre-breeding migration.
To investigate how differences in positions within the breeding range of a species impact post-breeding migratory behavior and thus exposure to risk, I tracked shorebird species from distinct parts of their breeding range.
Lesser Yellowlegs (Tringa flavipes) were tracked from nine sites across the entire species’ breeding range with 4g Pinpoint GPS transmitters to evaluate differences in migratory behaviors and connectivity. (A) Southbound migratory tracks of 95 Lesser Yellowlegs (Tringa flavipes) from breeding sites in Alaska and Canada, 2018–2021 and 2023–2024. Individuals tracked from James Bay and Mingan, Canada, did not fly through the Prairie Pothole Region and are not depicted. (B) GPS points of all T. flavipes within the Prairie Pothole RegionKernel density estimates within the Prairie Pothole Region of Lesser Yellowlegs from four breeding regions during early, mid, and late migration, 2018–2021 and 2023–2024. Colors represent different breeding groups, and shade represent utilization distributions at 95, 50, and 25% isopleths. Isopleths represent areas of equal probability of occurrence, with higher density contours indicating regions where individuals were more frequently observed.
Bathrick RE, Johnson JA, Ruthrauff DR, Christie KS, Courtemanche A, Gesmundo C, et al. Tringa flavipes (Lesser Yellowlegs) from separate breeding sites subdivide the Prairie Pothole Region in space and time during southbound migration. Ornithological Applications. 2026;duag048. https://doi.org/10.1093/ornithapp/duag048
(a) Short-billed Dowitchers (Limnodromus griseus caurinus) tracked from two Alaskan breeding sites during Fall migration. (b) Boxplots depict timing of departure from breeding grounds and arrival to latitudes associated with stopover sites and wintering sites: Arcata Marsh in northern California, San Diego Bay in southern California, and wintering sites along coastal Mexico.
Short-billed Dowitcher (Limnodromus griseus caurinus) were tracked from two sites along the Gulf of Alaska to evaluate how wind conditions within the Gulf of Alaska influence departure timing, route, and migratory speedBathrick RE, Johnson JA, Ruthrauff DR, Snyder R, Stager M, Senner NR. Migratory strategies across an ecological barrier: is the answer blowing in the wind? Mov Ecol. 2024;12:70. https://doi.org/10.1186/s40462-024-00509-2
Alaskan Shorebirds Post-Breeding Flyways
Flyways are corridors that migratory birds use to move between northerly breeding sites and more southerly non-breeding sites. Alaska is positioned at the meeting place of migratory flyways, hosting species during the breeding season that diverge in different directions across the hemisphere. With collaborators from across Alaska, I am defining the post-breeding migratory flyways of 15 Alaska-breeding shorebirds with tracking data amassed from 2005 - 2025 and evaluating the shared strategies of species that use them.