Harlequin Ducks (Histrionicus histrionicus) are small, colourful sea ducks that spend most of the year in coastal areas, migrating inland only long enough to breed along mountain streams (the only duck to do so in North America). As with other sea ducks (e.g., goldeneyes and mergansers), they tend to have a long lifespan, low productivity, and delayed breeding….We would like to thank Cyndi Smith for putting this great resource together and sharing it with BVN. If you are interested in sharing nature-related resources for the Bow Valley, please contact us.
Life history
In western North America, Harlequin Ducks winter in coastal waters from Alaska to northern California, although the Strait of Georgia and the Salish Sea on the east and south of Vancouver Island are winter hotspots for birds that nest in Banff National Park (BNP) (Smith and Smith 2003). They feed on aquatic invertebrates, small crabs and fish eggs in the shallow inter-tidal zone. It is during these winter months that males and females form pair bonds (usually for life) (Smith et al. 2000), and then the male follows the female back to her breeding area. Females generally return to the stream where they were hatched to breed (called natal philopatry). Young birds of either sex will stay at the coastal area as yearlings, and sometimes do not pair and return to breeding streams until three or four years of age.
Although a few single males arrive on the Bow River in mid-April, most of the ducks return in the first weeks of May. Harlequin Ducks feed by diving to the bottom of the stream, where they move rocks and pebbles to find the larvae of caddisflies and mayflies, freshwater snails or fish eggs. They frequently feed below riffles and rapids, using eddies to rest between dives. After feeding they often “haul out” to rest on mid-stream rocks or logs, and at the downstream end of gravel bars.
The male guards his mate from other aggressive males, while she feeds voraciously to build up nutrient reserves to lay eggs. Breeding females will sometimes re-use the previous year’s nest. Nests are usually located within a metre of rushing water, often on an island if available. Females that return to the Bow River almost always nest on tributaries such as Baker and Moraine creeks, and the Pipestone River.
The female lays one egg every other day, to an average of four to seven eggs in total. After all the eggs are laid (up to two weeks) the female will begin to incubate the eggs. During incubation she only leaves the nest once a day for an hour or two to feed, usually late in the day. At such times she covers the eggs with down to hide them from predators. Within days of the female beginning to incubate, her mate leaves the vicinity to meet up with other males, often referred to as a “bachelor club”. Most male Harlequin Ducks from the Bow Valley leave by the end of June, returning to the coast to undergo their annual flight feather moult, an approximately six-week process. As a result, if the nest is destroyed by a predator or high water, there is no second chance to nest like many other birds can. Females who do not raise a brood will also leave for the coast early.
Photo by Cyndi Smith.
After 28 days of incubation, the eggs all hatch within a few hours. Within 24-48 hours after hatching the hen leads her brood away from the nest, and often onto a larger stream to feed. They are already accomplished swimmers and feed themselves. At this stage they may have trouble diving because they are so downy and float well. They will eat insects from the water’s surface and from overhanging vegetation until they are proficient at diving. The hen is very alert and spends more time watching her brood than feeding. By about seven weeks of age the ducklings are flying (Smith 2020), but it might be a few weeks more before they migrate to the coast, following the female (Regehr et al. 2001). This is very unusual among birds, as most young migrate without the guidance of a parent.
Once they arrive at the coast, the female undergoes her feather moult. As long as they are both alive, the female almost always re-unites with her mate either at the moulting area or a common wintering area. This is amazing, considering that they have been separated for three to four months! During their first winter, male ducklings begin to show their colourful plumage, but it won’t be complete until the fall of their second year (Smith et al. 1998).
Survival and longevity
There are generally more males observed than females in a population because the females are more vulnerable to predators while incubating on the nest and while raising young (Bond et al. 2009). Predators on the breeding stream include mink, pine marten, red-tailed hawk, goshawk, and possibly owls. Ducklings are particularly vulnerable in their first few weeks of life, and it is a rare brood in which all ducklings survive to migrate to the coast. The main predator of all age groups at the coast are bald eagles, and harlequins have been seen to flee from river otters (although no predation has been recorded). The oldest recorded Harlequin Duck was an adult male banded in 1995 on the Bow River near Lake Louise, and last seen at the coast in 2014 at Hornby Island, BC, making him at least 20 years and 9 months old (Smith et al. 2017).
Species at risk status
Within North America Harlequin Ducks can be found along both the Atlantic and Pacific coasts. In 1990 the Harlequin Duck was listed as “Endangered” in eastern Canada, becoming the first North American duck to reach such critical status in modern times. With additional research and monitoring, the population was discovered to be small but stable, and the species was re-assessed as “Special Concern” in 2001. The Pacific population, while historically much larger than the Atlantic population, is showing signs of decline. Alberta does not have species at risk legislation, but the General Status of Alberta’s Wild Species considers Harlequin Ducks to be “Sensitive.”
The welfare of the Harlequin Duck appears to be intimately related to the availability of fastflowing, nonpolluted water, and streams where it can breed and nest away from human disturbance. It has been suggested that the Harlequin Duck’s dependency on undisturbed mature and old growth habitat, and streams with healthy macroinvertebrate populations makes it a good indicator of healthy aquatic ecosystems.
Research in Banff National Park
Public concern over declining Harlequin Duck observations in the Maligne River Valley of Jasper National Park, AB, prompted Parks Canada to initiate a study there in 1991. Jasper staff requested a summary of the general status and distribution of Harlequin Ducks within other mountain national parks, to help compare population data, behavioural changes and habitat requirements. In response, basic surveys were conducted in BNP from 1992-1994.
Observations to the end of 1994 showed that Harlequin Ducks were found throughout BNP. Although there had been sightings from 15 rivers and streams, and eight lakes, the Bow River appeared to be particularly important. On 07 May 1994 a high count of 93 Harlequin Ducks was made over a 28-km section of the Bow River between Lake Louise and Castle Junction. This translated into a density of 3.3 individuals/km, or a minimum of 1 pair/km. From the available literature, this represented a high density relative to other records of Harlequin Ducks on a breeding stream in North America.
In the mid-1990s, the proposed twinning of the TransCanada Highway (TCH), from Sunshine Junction to Castle Junction, and eventually to Lake Louise, had the potential to significantly impact a large number of Harlequin Ducks along the Bow River. The TCH (as well as the Canadian Pacific Railway and a pipeline) parallels the Bow River at a distance ranging from a few metres to a few hundred metres throughout the Bow Valley. The potential impacts of road, railway or pipeline construction on Harlequin Ducks and their breeding habitat include: destruction of riparian areas; disruption of watershed stability and stream flow regime, which can alter the invertebrate community structure; immediate and/or extended decrease in the food base due to increased sedimentation; isolation of brood-rearing areas by roads, and; disturbance from human activities related to construction or increased access after construction.
The high density of Harlequin Ducks on the Bow River, the close proximity of the river to the highway, the potential for highway impacts to be carried downstream, the species’ sensitivity to habitat modification, and the fact that the Bow River is near the periphery of the species’ range, were all cause for concern and led to intensive research from 1995-1999.
Disturbance of Harlequin Ducks (hiding, swimming away or flying away) by boats was found to be much lower (43%) on the Bow River than on the Maligne River (87%) in Jasper National Park. However, there has been no follow-up monitoring of human disturbance in the past 20 years, so it is unknown if there have been changes since the study. Guidelines were produced that encourage boaters to reduce their impact (Smith 1996). The final report (Smith 2000a) provided a number of recommendations regarding highway construction, and a monitoring plan (Smith 2000b) was written (some minor amendments were made to the plan in 2005).Parks Canada has continued to monitor Harlequin Ducks along the Bow River between the Twin Bridges (downstream of Lake Louise, just upstream of Lake Louise Rapids) and Castle Junction. The recommended roadside survey has been done annually since 1995 (except 2000), providing a long-term index of abundance. The mean annual count has significantly declined since 1995 (1995-2018 Roadside Survey Index). It is difficult for researchers to determine the underlying causes for the decline, which could include any combination of: actual decrease in numbers of birds; birds using different areas of the river that are outside of the survey area; changes to food sources; upgrades to the Lake Louise sewage treatment plant reducing nutrients in the water; changes in water regime (temperature, flow, timing) due to climate change, or; impacts to the population on the moulting and wintering areas.
Reporting Harlequin Duck sightings
Since 1995 researchers have periodically captured Harlequin Ducks in BNP and other jurisdictions and attached a uniquely numbered metal band to one leg and a plastic band to the other leg. The plastic band has a unique combination of colours and letters/numbers that allows individual birds to be identified without recapturing them. Because Harlequin Ducks often haul out on rocks or logs to rest and preen after feeding, an observer can use a spotting scope to read the band code (Report a Banded Harlequin Duck). Sightings of marked ducks help researchers to answer many questions about seasonal and annual movements, site fidelity, longevity, productivity, etc. Observations of females with broods are also important and can be reported in the same way.
Literature cited
Bond, J.C., S.A. Iverson, B. MacCallum, C.M. Smith, H.J. Bruner, & D. Esler. 2009. Variation in breeding season survival of female Harlequin Ducks. Journal of Wildlife Management 73(6):965-972.
Regehr, H., C.M. Smith, B. Arquilla & F. Cooke. 2001. Post-fledging broods of migratory Harlequin Ducks accompany females to wintering areas. Condor 103:408-412.
Smith, C.M. 1996. Boaters and Harlequin Ducks: guidelines for co-existence. Parks Canada, Banff, AB.
Smith, C. M. 2000a. Population dynamics and breeding ecology of Harlequin Ducks in Banff National Park, Alberta, 1995-1999. Unpublished Technical Report. Parks Canada, Banff National Park, Banff, Alberta, Canada. 107 pp.
Smith, C. M. 2000b. Harlequin duck monitoring plan for Banff National Park. Unpublished Technical Report. Parks Canada, Banff, Alberta, Canada. 37 pp.
Smith, C.M. 2020. How to identify juvenile Harlequin Ducks. Unpublished technical report. Bow Valley Naturalists, Banff, AB. 6 pp.
Smith, Cyndi M. & Constance M. Smith. 2003. Strait of Georgia, British Columbia – nonbreeding area for Harlequin Ducks that breed throughout the Pacific Northwest (poster). In:T. W. Droscher and D. A. Fraser (Eds), Proceedings of the 2003 Georgia Basin/Puget Sound research conference. CD-ROM or Online. Available: https://archives.eopugetsound.org/conf/2003GBPS_ResearchConference/SESSIONS/POSTER_1.htm [February 2017].
Smith, C.M., F. Cooke & R.I. Goudie. 1998. Ageing Harlequin Duck Histrionicus histrionicus drakes using plumage characteristics. Wildfowl 49:245-248.
Smith, Cyndi M., J. Ashley, R. Ian Goudie & Constance M. Smith. 2017. New longevity record for Harlequin Duck more than 20 years. North American Bird Bander 42(3):72-74.
Smith, C.M., F. Cooke, G.J. Robertson, R.I. Goudie & W.S. Boyd. 2000. Long-term pair bonds in Harlequin Ducks. Condor 102:201-205.
Links
https://www.allaboutbirds.org/guide/Harlequin_Duck/overview