Wetland bird use of anthropogenic landscapes on the Chignecto Isthmus
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Date
2025-08
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University of New Brunswick
Abstract
The Chignecto Isthmus is a land bridge that connects Nova Scotia to New Brunswick and is a critical juncture of the Atlantic Flyway, an internationally recognized travel route and management zone for migratory birds. Since the arrival of European settlers in the 1600s, the Isthmus has experienced significant changes. Vast saltmarshes were drained to create productive agricultural lands (“dykelands”), which led to considerable losses of wetland habitat. Human-made wetlands (“impoundments”) were introduced in the 1960s to compensate for losses of natural wetlands. In this dissertation, I explored how wetland birds use human-created landscapes on the Chignecto Isthmus, including dykelands and impoundments. In Chapter 2, through systematic literature review, I investigated if impoundments are providing habitat for birds, if bird use is being monitored, and if so, if that information is readily available. I found that despite impoundments being built for nearly a century, the number of resources detailing monitoring are scarce. Despite this scarcity, results suggest a mostly positive response by a variety of bird taxa to impoundments, but some papers noted wetland senescence. In Chapter 3, I interviewed local people who interact regularly with the land and wildlife to understand their perceptions of change on the Chignecto Isthmus. Many people perceived an increase in wetland area during their lifetimes, which they attributed to more impoundments. Other notable changes that participants discussed were changes in wetland productivity, agriculture, aerial insectivore numbers, and ways that people interact with wildlife. In Chapter 4, I tested a strategy for rejuvenating productivity in impoundments via water-level manipulations (“drawdowns”) through a before-after-control-impact study. Overall bird abundance increased with the post-treatment stage, but individual taxa showed mixed responses. In Chapter 5, I challenged a long-held assumption that the Acadian subspecies of Nelson’s Sparrow (Ammospiza nelsoni subvirgata) is a “saltmarsh specialist”. I investigated breeding habitat use and nest survival in saltmarshes and dykelands. Despite greater use of saltmarshes, nest survival was higher in dykelands. The results of my dissertation highlight the importance of human-made habitats for birds in areas with significant landscape changes, like the Chignecto Isthmus. My results also emphasize the importance of long-term monitoring and social considerations in decisions on landscape changes for bird conservation.