Changes in Numbers of Wintering American Black Ducks and Mallards in Urban Cape Breton Island, Nova Scotia

McCorquodale, D. B.; Knapton, R. W.

doi:10.2307/3858699

Cited by 2 publications

(3 citation statements)

References 9 publications

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“…Our results confirm previous analysis that suggested wintering American black ducks are stable or increasing in eastern Canada (McCorquodale and Knapton 2003;Link et al 2006). The survey, developed in 1970, does not provide data to address issues such as interobserver variation and imperfect detections, so it is not without potential biases (Pearse et al 2008).…”

Section: Discussionsupporting

confidence: 84%

“…Consistent with that idea, the BCR that experienced the greatest increases (4.3%/y) in the Christmas Bird Count analysis by Link et al (2006) was the Boreal Hardwood Transition BCR (BCR 12), which lies to the northwest of BCR 14 and Nova Scotia. McCorquodale and Knapton (2003) noted that the number of wintering black ducks increased in the urbanized areas of Cape Breton (Sydney and environs) between 1992 and 1999-2002. Our results for Cape Breton suggest that this increase is continuing and spans the entire data series.…”

Section: Discussionmentioning

confidence: 99%

“…Christmas Bird Count (a volunteer-based bird survey conducted in late December) data indicated increases in the northeastern United States in winter (Link et al 2006). Depending on ice severity, some black ducks have always wintered in Maritime Canada and observers in urban areas have noted local increases (Godfrey 1986;McCorquodale and Knapton 2003).…”

Section: Introductionmentioning

confidence: 99%

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Increases in the Number of American Black Ducks Wintering in Nova Scotia, 1970–2015

Robertson

Tomlik

Milton³

et al. 2017

Journal of Fish and Wildlife Management

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Despite extensive conservation and management efforts, American black duck (Anas rubripes) populations remain below desired population levels. Researchers have noted declines at a number of wintering areas, but indications are that wintering populations in the northern part of the range are increasing. Intermittently between 1970 and 1989, and annually since 1992, wildlife biologists have flown aerial surveys of the entire coast of Nova Scotia, Canada, to count wintering waterfowl. This survey counted the total number of ducks seen in predefined lengths of coastline. We analyzed those survey data using generalized linear mixed models, over the entire time period and in the recent time period (1992-2015, when surveys were done every year), across five general regions of Nova Scotia. We fit models using Bayesian methods with uninformative priors; models with negative binomial response distributions performed well. Due to the large variation in mean numbers of black ducks across the predefined lengths of coastline, we treated these blocks of coastline as a fixed effect, while annual trend (slope) was modeled as a random effect to account for variation in annual trend across blocks of coastline. Results were similar between the entire time series or the most recent and more complete time series . In general, numbers of wintering black ducks in Nova Scotia increased (1.0-16.0%/y) and increases were significant (Bayesian credible intervals did not bound 0) in four of five regions. Increasing numbers in Nova Scotia are consistent with other observations of increasing wintering numbers at the northern range of American black ducks and may indicate a shift in the wintering range that has been ongoing for decades. Future habitat management actions will benefit from consideration of regional trends and the distributional change of black duck.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%