Date of Award
5-2025
Rights
© 2025 Zishi Wu
Document Type
Thesis
Degree Name
Master of Science in Biological Sciences
Department
Environmental Science
First Advisor
Noah Perlut
Second Advisor
Will Kochtitzky
Third Advisor
Steven Travis
Abstract
Understanding movement ecology across life-history stages and among breeding populations is essential for conserving declining migratory species. The Bobolink (Dolichonyx oryzivorus), a grassland songbird, exhibits complex and flexible movement behaviors shaped by landscape, environmental, and intrinsic factors. In this study, we used two tracking methods—miniaturized satellite transmitters and light-level geolocators—to investigate space use, migration strategies, and population-level differences across the annual migration cycle.
In Chapter 1, we used satellite tags to track 31 male Bobolinks from two ecologically contrasting breeding sites in the northeastern U.S.—one large, continuous grassland and one small, isolated field. Using Continuous Time Movement Models, we compared breeding and post-breeding home range sizes and habitat composition, analyzed pre-migratory movements, and modeled fall stopover behavior. Males at the larger site maintained bigger breeding home ranges with greater grassland cover, reflecting landscape-driven variation in space use. By the post-breeding period, home range sizes converged between sites. We documented long-distance excursions (up to 17 km), likely linked to extra-pair mating, and revealed the first evidence of nocturnal pre-migratory flights in adult songbirds. During migration, precipitation and temperature influenced stopover duration, while landscape features did not explain variation in stopover home range size.
In Chapter 2, we analyzed data from archival geolocators recovered from 14 individuals to assess differences in migratory connectivity, phenology, route selection, and performance between our two populations separated by ~300 km. Despite ecological differences at breeding sites, we found weak migratory connectivity and largely similar migration performance. However, southern birds exhibited longer spring stopovers than northern birds. We also found sex-based differences in spring migration, with males using more inland routes and arriving ~11 days earlier than females in the second half of their journey. Fall migration was notably longer and marked by extended stopovers compared to spring, highlighting strong seasonal asymmetry in migratory behavior.
Together, these findings emphasize Bobolink’s behavioral plasticity and the importance of full-annual-cycle conservation. Conservation efforts should (1) protect broad-scale grassland habitat networks (≥800 ha) to accommodate breeding home ranges and facilitate excursive movements; (2) safeguard key stopover sites, especially in the Caribbean; (3) extend temporal protection to cover sex-specific and seasonal migration strategies; and (4) align conservation units with genetic population structure to preserve regional migratory behaviors in this declining grassland specialist.
Preferred Citation
Wu, Zishi "Violet", "Comparative Movement And Migration Ecology Of A 32g Songbird Across The Annual Cycle: Insights From Satellite And Geolocator Tracking" (2025). All Theses And Dissertations. 455.
https://dune.une.edu/theses/455
Comments
Master's Thesis