Migration chronology and movements of adult American black ducks Anas rubripes wintering in Nova Scotia, Canada

Abstract

American black ducks, native to eastern North America, have been the focus of significant international conservation and management programs. The combined USA and Canadian population has traditionally been managed as a single population; however black duck demographics may vary by region. To help understand potential regional differences in black ducks, we used satellite telemetry to assess migratory chronology and movements of black ducks wintering near Windsor, Nova Scotia, Canada, near the northern limits of their wintering range where numbers are increasing. Wintering black ducks from Nova Scotia did not leave the Atlantic Flyway and included both longer‐distance migrants (~ 1500 km north) and locally‐breeding individuals. None of our tracked ducks travelled south of Nova Scotia during any part of the annual cycle, indicating a population segment that never leaves Canada and is subject solely to Canadian harvest pressures. Band recovery data revealed that a small portion (2.4%) of black ducks originally banded during winter in Nova Scotia were recovered south along the east coast of the USA, indicating that some of these black ducks are subject to international harvest pressures. Our results show that there are differences in annual black duck movements even within a small part of their range, adding to the growing evidence that black duck populations show fine‐scale temporal and spatial structure. This structure will need to be considered in future interprovincial and international harvest management plans of this important species.

Origins of harvested American black ducks: stable isotopes support the flyover hypothesis

“…By incorporating these movement estimates, we inferred a Mississippi flyway stock produced in the Boreal Shield and Hudson Plains of Ontario that is harvested in the Great Lakes and interior of Canada and the United States and an Atlantic flyway stock harvested both as local breeders and with some migrants from northern Quebec and Newfoundland and Labrador in the Boreal Softwood and Taiga Shield. This supports the findings of Peck et al (2022), where some individuals spent the entire annual cycle in Nova Scotia, while others migrated north to breed. This is especially important because these interior regions showed more negative population trends compared to Atlantic Canada, although we did not model the northern breeding individuals because of inadequate BBS coverage in the northeastern and northwestern Canada black duck conservation regions.…”

“…Coluccy et al (2020) investigated only adult females and treated the breeding and molt location as the same. Although Peck et al (2022) did acknowledge that 2 of their 5 male black ducks may have exhibited molt migration to the north, they were not confident in classifying molt migration in these cases. Other tracking studies determining molt migratory movements have focused more on geese and diving ducks, where northward movements to molting sites such as the Hudson and James Bay lowlands and Ungava Peninsula are documented for eastern populations of these groups (Robert et al 2002, Sheaffer et al 2007, Luukkonen et al 2008).…”

“…This result has also been seen in mallards, where even at northern harvest locations early in the season, some northern‐produced individuals and some nearby breeders are harvested (Kucia 2021). Black ducks have been expanding their winter range farther north and east (Brook et al 2009) and some breeding individuals in Atlantic Canada, specifically in Nova Scotia, remain in Canada over winter (Peck et al 2022). If some individuals are permanent residents in this area, they should be available for harvest early in the hunting season with a larger proportion of the harvest representing boreal origins later in the season, especially because the harvest season for Canada generally begins as early as 1 September (range of start dates 2021–2022: 1–25 Sep in ON; 1–25 Sep in QC, 1–15 Oct in NB, 1–8 Oct in NS) compared to the United States (e.g., 25 Sep to 9 Oct in MI, 2 Oct to 20 Nov in NY, 27 Sep to 6 Nov in ME).…”

“…This result has also been seen in mallards, where even at northern harvest locations early in the season, some northern-produced individuals and some nearby breeders are harvested (Kucia 2021). Black ducks have been expanding their winter range farther north and east (Brook et al 2009) and some breeding individuals in Atlantic Canada, specifically in Nova Scotia, remain in Canada over winter (Peck et al 2022) Early boreal migrants arriving at the beginning of the harvest season in these northern areas likely obscure this temporal effect in natal and molt origin. In the southwestern Canada conservation region, the extremely low breeding densities of black ducks likely further prevent any temporal effects in origin because so few local black ducks are available to hunters early in the hunting season (compare abundance indices in Figure 2).…”

“…Coluccy et al (2020) investigated only adult females and treated the breeding and molt location as the same. Although Peck et al (2022) did acknowledge that 2 of their 5 male black ducks may have exhibited molt migration to the north, they were not confident in classifying molt migration in these cases.…”