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Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Hobson, Keith A.

Abstract

Naturally occurring stable isotopes within animal tissues can provide intrinsic markers for predictable assignment to origin of migratory animals, without additional tracking devices. The use of feather stable-hydrogen isotopes (δ2Hf) in waterfowl research has been limited until recently and the opportunity to use stable isotopes in general to inform waterfowl management, particularly when assessing source origins and connectivity, is unrealized. Many of the current waterfowl monitoring programs (e.g., preseason banding) are spatially limited due to accessibility, but intrinsic markers provide a complementary method to estimate harvest source areas and evaluate biases. In my Ph.D. dissertation, across four data chapters, I used δ2Hf measurements to inform direct connections between harvest and source areas for harvested waterfowl in eastern North America, assessing and improving on the current methods. First, I used δ2Hf and stable-carbon isotope (δ13C) measurements to evaluate differences in the origin of harvested American Black Duck (Anas rubripes) across its range (Chapter 2). I found evidence supporting the flyover hypothesis, where American Black Duck harvested in Atlantic Canada showed predominantly southern (local) origins, while those harvested elsewhere originated farther north in the boreal. Second, I critically evaluated the current methods used to predict origins based on stable isotopes in waterfowl feathers (Chapter 3). Here I aggregated known-origin calibration data (δ2Hf vs. δ2Hp) and informed the best practices for assignment methods moving forward. Lastly, focusing specifically on leg-band returns and how they can be directly integrated into likelihood-based assignment, I explored spatiotemporal patterns in the natal source areas of waterfowl in eastern North America (Chapter 4) and critically evaluated the use of band returns as a prior probability of origin, directly comparing source areas derived from band returns and δ2Hf measurements (Chapter 5). I found evidence of flyway-specific natal sources with northward shifts later in the harvest period. When used as a prior probability of origin, band returns greatly refined derived source areas, despite their spatial bias. Together, these contributions address key conservation questions for species of conservation concern, inform best practices when using stable isotopes, and demonstrate the value of stable isotopes as a tool for waterfowl management.

Summary for Lay Audience

Naturally occurring chemical markers stored within animal tissues can help us determine where migratory animals spend different parts of their life. For migratory ducks, these markers are useful when determining connections between areas where ducks breed or were raised and where they are hunted. These naturally occurring markers are beneficial because they do not require any initial capture or marking to gain information on a duck’s origin. Most often these connections are determined using metal leg bands. Banding only occurs in the south of Canada and across the continental United States because it is difficult to reach far northern areas, which may lead to errors when creating connections with breeding areas. In my research, I studied how we can use naturally occurring chemical markers in feathers to determine important breeding areas for hunted ducks. In Chapter 2, I investigated connections between breeding and hunting areas for a species of conservation concern, the American Black Duck. I found that American Black Duck hunted in Atlantic Canada bred in local areas. In all other hunting areas, ducks showed breeding areas in the northern forests of eastern Canada. In Chapter 3, I used feathers from ducklings raised in known lakes across North America and Europe to evaluate and improve the methods used to predict the chemical markers in duck feathers across the continent. In Chapter 4, I used leg bands to investigate how variable the connections between breeding and hunting areas are and how they change over the hunting season. I found that breeding areas matched hunting areas in the same flyway but hunted ducks had more northern breeding areas later in the hunting season. In Chapter 5, I used metal leg bands together with chemical markers to combine the two data sources and improve methods used to create connections between hunting and breeding areas for several duck species in eastern North America. I found that combining band returns with chemical markers to determine breeding origins allowed for more precise estimates. My research helps us understand and protect waterfowl by improving our ability to track their origins.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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