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Harlequin Duck (Histrionicus histrionicus)


3.1  Population Ecology

The Harlequin Duck (Eastern population) breeds on inland rivers and streams from northern New Brunswick north to Nunavut, and winters in coastal areas from Newfoundland, south to Maryland, as well as southwest Greenland.  Breeding habitat includes fast flowing river systems that may vary in width across the species range.  In northern Labrador narrower, warmer and less acidic rivers are preferred (Rodway 1998).  Multiple factors may impact river selection including acidity, physical features, food availability (Rodway 1998), and predator distribution (Heath 2001).  Wintering habitat consists of rocky coastline, exposed headlands, and subtidal ledges (see Robertson and Goudie 1999).  Harlequin Ducks are also regularly associated with offshore islands.

Population trends are not available for the breeding population of eastern North America.  The population has not been consistently nor systematically surveyed for a sufficient period to provide trends.  Local aboriginal knowledge from Innu elders of Davis Inlet (N55° 53.3', W 60° 54.5') suggested that Harlequin Duck populations in central Labrador declined considerably in the 1980s and early 1990s (Ryan 1994, Thomas 2001). Additionally, the Greenland wintering population trend is also unknown.  Only one completed survey has been conducted at Greenland moult sites in July and August of 1999.  No previous or subsequent surveys were completed.  The data is insufficient to generate a population size estimate, however a series of extrapolations estimated 5000–10 000 moulting individuals (Boertmann and Mosbech 2002).  The extent of the affiliation with Harlequin Ducks breeding in Canada is unknown, but may be important.

Satellite telemetry studies determined that Harlequin Ducks that bred in northern Québec and northern Labrador migrated to the southwest coast of Greenland to moult and winter (Brodeur et al. 2002).  Also, Robert et al. (in press) determined that some individuals wintering along the coast of Maine are known to moult in Greenland and return to Maine for the winter season.  However, of the estimated 5000 – 10 000 individuals moulting along the southwest coast of Greenland (Boertmann and Mosbech 2002), it is unknown how many are Canadian breeders. 

Continued surveys in Labrador and northern Québec have led to a greater understanding of Harlequin Duck distribution in northeastern Canada.  None of the northern breeding Harlequin Ducks tracked and/or banded by Brodeur et al. (2002), and Chubbs (in press) have been observed at moulting or wintering locations in eastern North America (Thomas et al. in press).  However, one Harlequin Duck banded in Hebron Fiord, Labrador (N 58° 06.9', W 63° 00.2') was observed at the Gannet Island moult site (N 53° 56.6', W 56° 30.9') that is closely associated with the eastern North American wintering location (Thomas et al. in press).  It is uncertain if this was anomalous. 

In eastern North America Harlequin Duck affiliations to their breeding, moulting and wintering sites are varied (Thomas et al. in press).  A series of banding and telemetry studies since 1997 have better defined some of the movement patterns of Harlequin Ducks throughout eastern North America.   As an example, a Harlequin Duck banded at Fig River/Lake (N 53° 06.8', W 63° 12.5') was resighted at its moulting site in Labrador - the Gannet Islands - and later at its wintering location along the coast of Maine (N 44° 8.2 ', W 68° 33.3'), and was subsequently recaptured at another moulting location along the southwest coast of Greenland (N 64° 12.5', W 51° 41').  Additionally, Robert et al. (in press) found that wintering individuals along the coast of Maine moulted in Greenland only to return to Maine for the winter.  It is not known if these individuals changed moult locations between years.  The level of uncertainty associated with the Greenland/North America Harlequin Duck connection prompts the need for improved communication and collaboration on Harlequin Duck monitoring and research initiatives.  This is of particular importance as most of the Harlequin Ducks breeding in northern Québec and northern Labrador likely moult and winter in Greenland, and thus face different stresses than wintering North American individuals.

The eastern North American wintering population has been surveyed with more success and regularity over the past 10 years.  Regular surveys at four strategic winter locations in eastern North America has indicated population increases at all sites since 1994 (Thomas and Robert 2001).  Similarly, Christmas Bird Counts (CBC) during this time period recorded higher numbers in many areas throughout Atlantic Canada and coastal Maine, USA (Thomas and Robert 2001).  The reliability of CBC data will vary throughout eastern North America.  While CBC surveys at Cape St. Mary’s, Newfoundland and Labrador have been conducted along the same route by comparable and competent surveyors for 25 years, other areas have received less frequent and inconsistent efforts.  As a result, CBC data for some areas must be interpreted guardedly. 

The Harlequin Duck wintering population in eastern North America was once estimated to be less than 1000 individuals (see Montevecchi et al. 1995).  However, in recent years there have been indications of population increases in parts of their range.  The Eastern Shore Management Area of Nova Scotia has experienced a substantial increase in population.  In 2001 there were an estimated 317 Harlequin Ducks observed during Canadian Wildlife Service (CWS) surveys.  In 2005, this number increased to an estimated 651 individuals (A. Boyne pers. comm.).  Surveys at Cape St. Mary’s Ecological Reserve in Newfoundland and Labrador have determined an increase in this area as well.  In 2001 a CWS boat survey estimated 91 individuals in the area, but that increased to 242 in 2005 (P. Thomas, pers. comm.), up from a low of approximately 20 individuals observed in 1990 (Montevecchi et al. 1995).  However, population levels in other areas of their range have remained relatively stable such as The Wolves, New Brunswick and Jericho Bay, Maine. 

Despite the localized population increases, the whole of the eastern North American wintering population is still estimated to be less than 3000 individuals, and probably well below historic levels for Atlantic Canada and coastal United States (Palmer 1949, Goudie 1989, Montevecchi et al. 1995).  Boardman (1903) reported 500 Harlequin Ducks at The Wolves, New Brunswick during the winter of 1875. Peterson and Fisher (1955) reported hundreds of Harlequin Ducks at Cape St. Mary’s, and Downs (1888) considered Harlequin Ducks rather common in Nova Scotia during the winter months.  However, the Mi’kmaq of Nova Scotia have stated that they believe the Harlequin Duck to have always occurred in low numbers (M. Cox pers. comm.).

Harlequin Ducks require fast moving streams with abundant invertebrate life during the breeding season (see Robertson and Goudie 1999).  The specific factors that make a river attractive to a Harlequin Duck will vary among regions, but moulting and wintering habitat requirements tend to be similar (see Robertson and Goudie 1999).  In eastern areas, moulting and wintering Harlequin Ducks congregate near exposed headlands and over subtidal ledges (Mittelhauser 2000).  Winter locations are determined largely by prey availability (Robertson and Goudie 1999), and they often stay close to shore (Hirsch 1980, Goudie and Ankney 1986).

3.2  Threats to Populations and their Habitats

The threat level to the eastern Harlequin Duck varies across its range.  The more northern breeders are generally faced with fewer threats during the breeding season than the eastern North America wintering population that breeds, by and large, in southern Labrador, the Gaspé Peninsula of Québec, the Québec North Shore, insular Newfoundland, and northern New Brunswick (Thomas and Robert 2001). Additionally, some individual Harlequin Ducks may cross through northern and southern sections of the species’ range within any given year.  As a result, it is difficult to assign threat severity without assessing all occupied regions for each specific threat.

Land use practices in some areas of the Harlequin Duck range could adversely impact the species.  Harlequin Ducks are susceptible to disturbance on their wintering, moulting, and breeding grounds (Robertson and Goudie 1999).  On breeding sites logging and hydroelectric development may pose threats to the habitat of the species (see Robertson and Goudie 1999).  In the wintering and moulting locations, fishing nets (see Robertson and Goudie 1999), aquaculture development, illegal/accidental harvesting, boating activities, and chronic and catastrophic oiling are potential threats (Thomas and Robert 2001).  

Hunting was a major factor that led to the low population estimate in the 1980s (Goudie 1990).  The legal hunt for the Harlequin Duck has been closed in the Atlantic Flyway since 1990.  While Harlequin Duck numbers are increasing at key wintering locations, consistent loss of Harlequin Ducks due to hunting is reported annually and remains a concern of management agencies.  Much of this loss may be attributed to misidentification. Insufficient hunter education is the key component contributing to this activity.  In Greenland, hunting of Harlequin Ducks has been banned since the 1960s, however periodically small numbers of Harlequin Ducks have been observed at local markets.  There is no quantitative data to further illustrate this threat.

The wide distribution of Harlequin Ducks across eastern North America is an indicator that habitat is available for this species.  The breeding range is large and difficult to survey accurately for population size and trend.  However we are aware that there are multiple issues potentially affecting Harlequin Duck breeding habitat throughout their breeding range.  Moreover, their primary wintering sites are still limited to less than 10 key locations in eastern North America (Thomas and Robert 2001).  As a result, a primary recommendation of this plan will be the development of a comprehensive threat assessment(s) to properly quantify the impacts of the possible threats to these sites, as well as the relative significance of these threats among the various regions.

3.2.1 Pollution

Oil/Bilge contamination and Shipping

Perhaps the most significant threat to the North American wintering population of Harlequin Duck in eastern Canada is the potential for oil contamination.  To date only a few incidents of oiled Harlequin Ducks have been reported in eastern Canada.  However there are substantial shipping routes along eastern Canada’s coastline that are in close proximity to Harlequin Duck wintering locations.  Potential for a large spill near an important Harlequin Duck wintering population is a possibility.  Illegal oil discharge in eastern Canadian waters have negative impacts on local bird populations.  It has been estimated that up to 300,000 individual seabirds may die every year due to offshore oil discharge from tankers, cargo and container vessels (Wiese et al. 2004).  Oiling events in southeastern Newfoundland in 2005 and 2006 were known to kill many Long-tailed Ducks, Common Eiders and seabirds (G. Robertson and S. Gilliland, pers. comm.).  In March 2005, a spill of unknown origin killed an estimated 1100 Common Eiders (S. Gilliland, pers. comm.), and in 2006 dozens of Long-tailed Ducks were also observed as oiled as a result of a spill of unknown origin (S. Gilliland, pers. comm.).  Harlequin Ducks often share wintering habitat with both these species.  

Invertebrate Control

Harlequin Ducks are known to feed on aquatic insects during their breeding season.  As a result, any insect control programs on breeding rivers may have deleterious impacts on the Harlequin Duck.  There is little documentation on this type of disturbance, and it is likely not a substantial threat in eastern North America.  However, with increasing recognition of the West Nile virus in eastern Canada, there is a higher likelihood of expanded spray programs.

3.2.2 Habitat Loss or Degradation

Hydro Development

Hydroelectric development has the potential to greatly alter water dynamics over large areas.  During the development of the Churchill Falls hydroelectric project, 1400 km² of land was flooded by the now Smallwood Reservoir.  This in turn was estimated to have displaced 3740 pairs of diving ducks, including Harlequin Ducks (Gilliland 2001). Negotiations are ongoing for expanding the Churchill River hydroelectric program into the Lower Churchill River Valley.  Additionally, there is hydroelectric development within Québec, however it is not certain how previous hydroelectric projects may have impacted the population in that Province.  The possibility of reactivating the Great Whale hydroelectric project in Québec has been discussed in recent years.  If this project were to go ahead there is a high potential to displace Harlequin Ducks from traditional breeding areas (Morneau et al. in press).  Additionally, there is the potential for small scale hydro development within the Harlequin Duck breeding range.  These projects may impact Harlequin Duck breeding habitat, and each proposal should be reviewed and mitigated accordingly.


Forestry operations continue to expand into known Harlequin Duck breeding areas.  Logging activities are known to remove suitable breeding habitat and also increase stream siltation that may affect food availability (Breault and Savard 1991, Crowley and Patten 1996).  It is difficult to fully assess the impact of forestry across the range of the Harlequin Duck due to the fact that the majority of breeding occurs in areas that are not presently exploited by the forest industry.    

Resource extraction

Mining exploration continues to increase in eastern Canada, most notably in Newfoundland and Labrador, and may impact on Harlequin Duck breeding locations (see Robertson and Goudie 1999).  For example, breeding site surveys conducted in 2005 counted 59 adult Harlequin Ducks on 10 rivers in the area of the Voisey’s Bay mining site.  Siltation, pair displacement and habitat loss are anticipated for this area that may displace some of these individuals (Voisey’s Bay Environmental Assessment Panel 1999).

3.2.5 Accidental Mortality:


Gill nets are a potential source of mortality for the Harlequin Duck (see Robertson and Goudie 1999).  However due to a decrease in inshore fishing activities in eastern Canada, it is not expected to be a substantial threat.  Gill net by-catch may be a more substantial issue in Greenland.

3.2.6 Aquaculture

Aquaculture activities continue to increase in Atlantic Canada, in places conflicting with known wintering locations for the Harlequin Duck.  Aquaculture operations established on or near Harlequin Duck wintering or moulting sites may cause the abandonment of these locations.  Also, Harlequin Ducks could potentially become entangled in gear and/or the machinery needed to run the operation.  As the potential for overlap increases with time, there is a greater need for improved understanding and research of these activities on the species.  These types of limiting factors are more relevant to Maritime Canada.

3.2.7 Disturbance and Persecution:

Aircraft Disturbance

The effects of low-level flying military aircraft on Harlequin Ducks were studied in Labrador (Goudie 2003).  Results from this study indicated a behavioural response to low-level flying aircraft in southern Labrador.  However, there was insufficient data to definitively determine any population level impact on the species.     

Human disturbance

Harlequin Ducks are tolerant of moderate levels of disturbance (Savard 1988, Clarkson 1994, Brodeur et al. 1998), but they will abandon a site when the disturbance becomes chronic (Cassirer and Groves 1991, Clarkson 1994, Hunt 1998).  Most of the breeding locations for this species in eastern Canada are remote and free from human disturbance.  However for some areas in the southern extent of their breeding range (i.e. northern Newfoundland, southern Québec and New Brunswick) disturbance may play a role in reducing breeding success.  Disturbance events may include recreational boating, angling, and chronic human presence.  Wintering and moulting locations may be impacted by boating and shipping traffic.  Recreational boating may play a role in disturbance on breeding rivers in more southern areas such as Newfoundland , the Gaspé Peninsula, and northern New Brunswick.  Rivers in these areas are more accessible and therefore more susceptible to recreational activities. Large scale rafting is known to be disruptive to Harlequin Ducks (Hunt 1998), and recreational fisherman may present a problem due to the fact that they remain along the streams and rivers for long periods of time (Wallen 1987).

3.2.8 Consumptive Use: 

Illegal hunting

Hunting of the Harlequin Duck was thought to be the primary reason for their noted decline in the 1970s and 1980s that ultimately led to their endangered status rank in 1990 (Goudie 1990).  As a result, hunting of Harlequin Ducks was restricted in 1989 when the hunt was banned in the Atlantic Flyway.  However, Harlequin Ducks are annually reported to be illegally and accidentally hunted (see Thomas and Robert 2001).  Hunting is still thought to be a threat to the Harlequin Duck population.

Harlequin Duck behaviour also plays a role in the accidental hunting of Harlequin Ducks.  The species often mixes with other seaduck species and are sometimes misidentified due to these affiliations.  Again, there is little quantitative data, however, further elaboration on the subject could be highlighted in the proposed threat assessment for the species.

3.3  Monitoring History

There has been limited long-term survey effort of Harlequin Ducks in eastern North America.  The following is a summary of monitoring and survey efforts conducted throughout eastern Canada.


  • Rodway (1998) did surveys and habitat assessment for the Harlequin Duck in northern Labrador.
  • Gilliland et al. (2002) conducted aerial surveys of the Labrador coast in 1994 for moulting and staging Harlequin Ducks.
  • Extensive survey efforts were conducted at the Voisey’s Bay mine site as part of their Environmental Assessment for the project (Voisey’s Bay Environmental Assessment Panel 1999).
  • The Department of National Defence conducted survey efforts and research projects to assess movement patterns within south-central area of Labrador (JWEL 1998, JWEL 1999, and Chubbs et al. in press).
  • In southern Labrador, the Canadian Wildlife Service has been conducting regular surveys of the Gannet Island moult site since 1998 (Adams et al. 2000) and Trimper et al. (in press).
  • Heath (2001) monitored several river systems in northern Labrador.
  • Joint surveys were conducted with the Provincial government, CWS and other partners in the late 1980s and early 1990s along multiple river systems in Labrador.


  • Two intensive satellite telemetry projects have been conducted in Québec to determine movement patterns and distribution of Harlequin Ducks (Brodeur et al. 2002, Robert et al. in press, Savard et al.in press). 
  • Helicopter surveys of the Québec North Shore, Anticosti Island and Gaspé Peninsula watersheds (Robert 2000, Robert et al. 2001), as well as in the James and Hudson Bays (Morneau et al. in press).
  • Study of the habitats used and the movements of females and young Harlequins in the Gaspé Peninsula (Brodeur et al. in press).
  • Surveys and studies during the moulting stage in the Gaspé Peninsula and Anticosti Island (Gilliland et al. 2002, Langlois 2005).
  • Christmas Bird Counts in Québec.
  • Hydro-Québec monitoring Harlequin Ducks and general waterfowl surveys (Consortium Gauthier-Guillemette-GREBE 1993a and 1993b)


  • Gilliland et al. (2002) conducted moult and stage site surveys in the northern part of insular Newfoundland.
  • Periodic survey effort of breeding rivers on Great Northern Peninsula by CWS and Parks Canada (S. Gilliland pers. comm.).
  • Regular surveys at Cape St. Mary’s Ecological Reserve wintering site by the CWS and the Provincial government.
  • Christmas Bird Counts in Newfoundland

Maritime Canada

  • Long standing surveys have been conducted on islands off the coast of New Brunswick by CWS and the Provincial government.
  • Intensive survey effort in 2000 and 2001 at White Head Island and less intensively along the remainder of the southern coast of New Brunswick.
  • Incidental and dedicated ground, air and boat surveys in Nova Scotia and New Brunswick by CWS staff (A. Boyne and P. Hicklin pers. comm.).
  • Christmas Bird Counts in Nova Scotia and New Brunswick. 

3.4  Knowledge Gaps

Definitive demographic parameters required for accurate population projection and survival models have yet to be determined.  Multiple sources of data are available, and must be compiled, combined, and analyzed.  Data analysis of completed mark-recapture studies will provide some demographic values representative of the eastern North American population.  There are also questions with regard to genetic relationships among Greenland and eastern North American populations of Harlequin Ducks which speak to population structure and management units. The extent of threat and the potential impact of those threats to the Harlequin Duck population are not known.  A threat assessment would provide insight into the threats to the population and their potential impact in the various regions of Atlantic Canada and Québec.  There is a lack of available baseline information regarding Harlequin Duck habitat making it difficult to develop a predictive habitat model.

3.5 Recommended Approach / Scale for Management

Harlequin Ducks use a variety of habitat types throughout their annual cycle.  The threats impacting the species are substantial and ubiquitous throughout much of their range.  As a result, conservation of the species must be focused at the population level as focusing on only a few locations would not suffice.  Maintaining population monitoring, better quantifying threats, and protecting habitat locations known for high concentrations of Harlequin Ducks is important.

At this time, Harlequin Duck management and conservation is being conducted independent of other Species at Risk in Atlantic Canada and Québec.  There are few other species and no Species at Risk that share a similar habitat and life cycle as the Harlequin Duck, and therefore a multi-species approach is not applicable.  In the event that another species becomes listed that shares Harlequin Duck habitat, a multi-species approach to conservation and management could be considered.