Master of Science
Hobson, Keith A.
Rubin, Benjamin D.
The Northern Pintail (Anas acuta) is a waterfowl game species with North American population levels consistently below long-term management goals. Native habitat loss to agriculture likely reduced recruitment and limits population growth. My objective was to provide a proof-of-concept approach to using stable isotope ratios (δ2H, δ13C, δ15N) in feathers to infer spatial origins and habitat selection to complement existing pintail management. I found 46% of all sampled pintails had likely moult origins in the boreal biome, compared to 32% estimated by breeding population survey and 55% of recruitment of young took place in the northern boreal region of Canada. I determined the source of pintail harvest in eastern North America which included areas in Atlantic Canada and the mid-continent. Wildlife managers can use these findings to inform adaptive harvest management protocols and better represent the regional heterogeneity of population parameters such as recruitment related to origins as described by my results.
Summary for Lay Audience
The Northern Pintail (Anas acuta) is a hunted duck species despite populations being below long-term management goals for the past 30 years. Wildlife biologists attributed the declines to the loss of native prairie habitat due to agriculture. While wildlife agencies have set sustainable harvest protocols for the pintail, current methods of estimating pintail populations and productivity are insufficient to cover the species’ broad geographic range.
I used stable isotope ratios in pintail feathers to determine the likely origin of harvested pintails. Stable isotope ratios work on the principle of ‘you are what you eat’, meaning the isotope ratios of food and water are incorporated into an organism’s tissues. Feather isotope ratios do not change once feathers are grown, and so are an excellent candidate tissue to infer moult origins. Ducks replace flight feathers before fall migration, so these feathers are linked to breeding areas. I used stable hydrogen isotope ratios (δ2H) to determine where each feather sample was grown. Precipitation is the main source of hydrogen in food webs throughout North America and stable hydrogen isotope ratios show predictable spatial patterns. I assigned samples to likely origins on a continental scale by linking amount-weighted mean annual precipitation δ2H to feather δ2H. Of my sample, 46% of pintails had δ2H values consistent with the boreal biome, compared to aerial-ground survey breeding population estimates of 32%. Of my hatch-year samples, 55% had δ2H values consistent with the boreal biome, compared to only 22% being consistent with the prairies. I used stable carbon (δ13C) and nitrogen (δ15N) isotope ratios to assign individuals to different biomes based on different ecosystems and levels of agricultural disturbance or marine inputs. While I was unable to fully separate different habitats based on isotope ratios, my results are consistent with previous literature.
My results underline the importance of the boreal zone as a breeding area for harvested pintails, which would not be possible to determine using current management techniques. These results are consistent with previous research that the prairies are not as productive for pintails as they once were. I recommend re-evaluating the heterogeneity of the continental pintail population and continuing stable isotope ratio analysis into future years.
Wojtaszek, Dariusz, "Using Stable Isotope Techniques To Complement Existing Northern Pintail Management." (2022). Electronic Thesis and Dissertation Repository. 9119.