Harlequin Ducks in the Canadian Maritime Provinces

Increased abundance and range expansion of harlequin ducks Histrionicus histrionicus wintering in Eastern Canada

“…Here we provide the current state of knowledge of harlequin duck wintering abundance, distribution, and trends in Eastern Canada. Our results indicate that numbers have continued to rapidly increase since the last reported positive trends (Boyne 2008, Thomas 2008, Bowman et al 2015, and wintering birds are likely expanding into new areas. Based on analyses presented here for the Atlantic Provinces of NL, NS, and NB, combined with an additional ~200 birds estimated to winter along the south coast of the Gaspé Peninsula in Québec (CWS Waterfowl Committee 2020) and another ~500 birds wintering around Ile St. Pierre of SPM (L. Quénéé pers.…”

“…Harlequin duck wintering sites on insular NL, NS, and NB have been identified and surveyed at irregular intervals and from varying platform types over the period 1988 to 2021 (all survey data are provided in Tables S1-S3 in the Supplement at www.int-res.com/articles/suppl/n049p187_supp.pdf). Surveys from helicopters or fixed-wing aircraft have included dedicated efforts to count harlequin ducks as well as general coastal waterfowl counts, while boat and land-based surveys have typically been used only to target known harlequin duck wintering sites (see Boyne 2008 andThomas 2008 for more detailed accounts). Eight historically surveyed regions in NS and NB (4 each) and 1 in NL are considered the major wintering areas and have been used to generate winter abundance estimates for Atlantic Canada in the past (e.g.…”

“…Eight historically surveyed regions in NS and NB (4 each) and 1 in NL are considered the major wintering areas and have been used to generate winter abundance estimates for Atlantic Canada in the past (e.g. Boyne 2008 andThomas 2008, respectively; Fig. 1).…”

“…Two types of winter harlequin duck survey data are generally available, each with unique limitations. First, targeted surveys have been conducted throughout Eastern Canada since the late 1980s in localized regions known historically to support wintering harlequin duck populations (Boyne 2008, Thomas 2008, Bowman et al 2015. These surveys have varied over time in spatial coverage, timing, and survey platform type, but have been more consistent and frequent since 2013.…”

“…Available data from both survey types in Maritime Canada up to 2003 (Boyne 2008) and the island of Newfoundland up to 2007 (Thomas 2008) suggested increasing abundance at wintering sites through the late 1990s and into the 2000s. Subsequent analysis for Atlantic Canada also suggested a general increase since the mid-1980s (CWS Waterfowl Committee 2020), as well as a more refined estimate for the rate of population change of 8.6% per year from 2001 to 2013 (Bowman et al 2015).…”