Banding waterfowl prior to the fall harvest has been a mainstay of waterfowl monitoring, management and research since the 1960s. The data provided through management agency efforts during summer banding on the breeding grounds and citizen science recovery and reporting during winter harvest are critical to inform populations dynamics, migratory connectivity and harvest management. But what about those harvested ducks without a leg band? Can anything be learned from them? Indeed, it can. When feathers are formed, a stable isotopic signature derived from the surrounding environment is sealed in the feather. These isotopic signatures vary predictably across broad regions thus allowing researchers to use these natural intrinsic markers to identify a duck’s regional summer origin through different values of the stable hydrogen isotope, otherwise known as deuterium. Although the precision of specific locations of origin is coarser than that derived from banding, the strength of the isotopic approach is that prior capture and leg banding is not necessary. In contrast, assessing migratory connectivity using banding data requires capturing an individual twice, once during summer on the breeding grounds and a second time on the winter grounds.

Shannon Stemaly (M.S.; Fowler), funded by the Louisiana Department of Wildlife and Fisheries and the Arkansas Game and Fish Commission, is assessing the summer origins of multiple duck species harvested in different regions of Arkansas and Louisiana with stable isotope techniques. She is then comparing the isotopic data from harvested birds to those derived from traditional band recovery data to determine the effectiveness of isotopic sampling. To do this, Stemaly and collaborators conducted an extensive sampling effort across Arkansas and Louisiana during the winters of 2022-2023 and 2023-2024. Throughout each hunting season, Stemaly collected feathers from hunter harvested-individuals across six duck species: mallard, gadwall, lesser scaup, blue-winged teal, green-winged teal and northern pintail.

Preliminary results for pintail challenge long-term banding data. In the last twenty years, 609 banded pintails have been recovered and reported in the state of Louisiana. Based on these data, Louisiana band recoveries of pintail are predominately from individuals captured and banded in the eastern Dakotas or southern Alberta and Saskatchewan (Figure 1). However, Stemaly’s feather analysis indicates that over 54% of nonbanded adults and 64% of nonbanded juvenile pintails harvested in Louisiana had summer origins north of these dominate banding locations (Figure 2).

So, what does this mean? While the data are preliminary, they suggest that isotopes may have identified biases in the banding data. The majority of banded pintail harvested in Louisiana are caught and marked in the southern extent of their breeding range, but deuterium analysis suggests that the majority of the Louisiana sample originates from more northern geographies. Only about 40% of harvested pintail supported deuterium values consistent with more southern breeding geographies where banding effort is more intensive. Thus, the isotopic analysis supports the idea that Louisiana provides winter habitat for pintails that originate across the latitudinal breeding distribution of the species. These results specifically highlight the importance of boreal, taiga, and arctic plains wetland habitat as a source of pintail productivity, at least based on the one year of data analyzed. The Prairie Pothole Region has historically been considered a stronghold for breeding pintail, but drought regimes and continued habitat loss may be limiting productivity relative to other areas of the breeding range. Additional years of data will be necessary to determine whether this is a long-term pattern or simply a response to current poor conditions in the prairie potholes.

In addition to these results, isotopes may also provide a means to challenge the long-held assumption that birds banded on a given wetland are of local origin and not a migrant from another location. Dr. Drew Fowler and Stemaly next plan to sample deuterium from individuals at the time of capture and banding to quantify the proportion of birds of local origins versus migrants at time of banding and how this proportion varies across the preseason banding window from late July to mid-September. By evaluating these foundational assumptions, scientists can modify current approaches to strengthen banding efforts and improve data quality for waterfowl management. Stay tuned for these results

Figure 1. Proportional banding origins of northern pintail harvested in Louisiana from 2003-2023 summarized across five-degree longitudinal and latitudinal lines.

Figure 2. A) Distinct regions of origin for northern pintail harvested in Louisiana during the 2022-2023 hunting season (n = 298) based on spatial statistical assignment using feather deuterium. B) Proportions of northern pintail assigned to each cluster by age. Bars in panels A and B represent the proportion of each age assigned to each region, while numbers within bars are the number of individuals assigned to each region.