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Harlequin Duck - Histrionicus histrionicus
State Rank Reason (see State Rank above)
The Harlequin Duck has an extremely limited breeding range in Montana.
- Details on Status Ranking and Review
Harlequin Duck (Histrionicus histrionicus) Conservation Status Review
Review Date = 09/15/2008
Population Size
ScoreC - 250-1,000 individuals
Comment250-1,000 adults
Range Extent
ScoreF - 20,000-200,000 km squared (about 8,000-80,000 square miles)
Comment150767 square kilometers based on Natural Heritage Program range maps
Area of Occupancy
ScoreG - 2,000-20,000 km squared (500,000-5,000,000 acres)
Comment3255 square kilometers based on GAP predicted model.
Long-term Trend
ScoreD - Moderate Decline (decline of 25-50%)
CommentA number of streams surveyed relatively recently (1980s and 1990s) no longer have breeding pairs or the number of breeding pairs are reduced.
Short-term Trend
ScoreD - Declining. Decline of 10-30% in population, range, area occupied, and/or number or condition of occurrences
CommentMarket hunting on coastal breeding grounds, loss of forest cover and subsequent alterations to streams since arrival of Europeans.
Threats
ScoreA - Substantial, imminent threat. Threat is moderate to severe and imminent for most (>60%) of the population or area.
CommentClimate change impacts to stream flow, human encroachment and activity on breeding streams
SeverityModerate - Major reduction of species population or long-term degradation or reduction of habitat in Montana, requiring 50-100 years for recovery.
CommentWhen stream flows are reduced breeding populations are reduced or eliminated.
ScopeHigh - > 60% of total population or area affected
CommentReductions in snow pack and stream flow and increases in human activity on breedings felt across range in Montana.
ImmediacyHigh - Threat is operational (happening now) or imminent (within a year).
CommentPopulations on several streams on the lower Clark Fork River are no longer present due most likely to reduced water flows
Intrinsic Vulnerability
ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
Environmental Specificity
ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
CommentMountain streams.
General Description
The Harlequin Duck is unique among North American waterfowl for breeding and foraging in clear, fast-flowing rivers and streams. The breeding plumage of adult males is unmistakable, with slate blue, white, black, and chestnut markings. This species is also unusual in its vocalizations; males and females give a mouselike squeak. The Harlequin Duck overwinters along coastal rocky shorelines (Robertson and Goudie 1999).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see
Marks et al. 2016, Birds of Montana.Phenology
In Montana, adults arrive from late April to early May (Kuchel 1977, Reichel and Genter 1996). Males depart breeding grounds in June while females and young depart from late July to early September (Kuchel 1977, Reichel and Genter 1994). Egg-laying occurs between April 30 and July 4 (Kuchel 1977, Reichel and Genter 1996). Kuchel (1977) estimated hatching dates for broods on McDonald Creek, Glacier National Park: 13 of 15 occurred between June 27 and July 7 with extremes on June 11 and August 2. Young fledge in Montana between July 15 and September 10, with most fledging between July 25 and August 15 (Kuchel 1977, Reichel and Genter 1996). Transients and winter observations recorded from October-March. Pairs observed beginning in April and May (Montana Natural Heritage Program Point Observation Database 2014).
Diagnostic Characteristics
The Harlequin Duck is a small diving duck. Male is larger than female. Breeding plumage of male is unmistakable: the body is slate blue with white bands and collars, bordered with black lines on chest and neck; large white crescent in front of eye with small white circular patch near ear; white vertical stripe on side of neck; black streak bordered by white and amber lines on top of head; iridescent blue secondaries; dark-slate-blue belly and chestnut-brown flanks. Adult female has brown body plumage, a white belly, with brown checks or spots, a round white spot behind ear, faded variable white patches in front of eye, and occasionally white streaks on back of head. Juveniles and immatures are similar to female, but feet are typically yellow, not gray (Robertson and Goudie 1999).
Species Range
Montana Range
Range Descriptions
Western Hemisphere Range
Range Comments
This species breeds in and along fast-moving, clear mountain streams, in western Montana. Regions with known breeding locations include the Absaroka/Beartooths, Middle and Lower Clark Fork, the Rocky Mountain Front, South Fork Flathead River, Glacier National Park, and the North Fork Flathead River. Observed in fall and winter in appropriate habitat (Montana Natural Heritage Program Point Observation Database 2014), but most individuals migrate to the west coast (Robertson and Goudie 1999).
Observations in Montana Natural Heritage Program Database
Number of Observations: 5378
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Regularly Observed
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
Migration
Harlequin Ducks breeding in Montana arrive primarily from late April to early May (Kuchel 1977, Reichel and Genter 1996). Males depart in June while females and young depart from late July to early September (Kuchel 1977, Reichel and Genter 1994). Twenty-four birds banded in western Montana have been sighted off of Oregon (2), Washington (1) and southern British Columbia (21) (Ashley 1995, Reichel and Genter 1996).
Habitat
In Montana, Harlequin Ducks inhabit fast moving, low gradient, clear mountain streams. In Glacier National Park, birds used primarily old-growth or mature forest (90%); and 2) most birds in streams on the Rocky Mountain Front were observed in pole-sized timber (Diamond and Finnegan 1993). Banks are most often covered with a mosaic of trees and shrubs, but the only significant positive correlation is with overhanging vegetation (Diamond and Finnegan 1993, Ashley 1994).
The strongest stream section factor in Montana appears to be for stream reaches with at least two loafing sites per 10 meters (Kuchel 1977, Diamond and Finnegan 1993, Ashley 1994). Broods may preferentially use backwater areas, especially shortly after hatching (Kuchel 1977), though this is not apparent in data from other studies (Ashley 1994). Stream width ranges from 3 m to 35 m in Montana. Harlequin Ducks in Glacier National Park used straight, curved, meandering, and braided stream reaches in proportion to their availability (Ashley 1994).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
mtnhp.org/requests) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Literature Cited
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
Food Habits
Diet includes young and adult aquatic insects and fish roe. Birds dive to pick food from the surface of cobbles and gravel. This species will also pick food from the surface of the water (Robertson and Goudie 1999).
Ecology
In Montana, 53% of adult males returned to their breeding streams from the previous year, while females returned at a rate of 57% (Reichel and Genter 1996). Of 58 juveniles marked in 1992, at least 12 females and 2 males were alive in 1994 (Reichel and Genter 1996). All females known to be alive have returned to their natal streams, but no males have returned (Reichel and Genter 1996). Nearly all duckling (through fledging) mortality apparently occurs during the first 3 weeks following hatching (Kuchel 1977).
Densities of Harlequins in Montana range from 0.05 to 0.21 pairs per stream kilometer on the Rocky Mountain Front to 0.67 to 0.91 pairs per stream kilometer on McDonald Creek (Kuchel 1977). Linear home ranges averaged 7.7 km on McDonald Creek (Kuchel 1977). Four relatively long distance movements between streams, across large reservoirs or lakes, have been reported in Montana ranging from 16 to 31 km (Reichel and Genter 1996).
Reproductive Characteristics
Adults arrive as pairs on the breeding grounds. Female creates a nest scrape; nests are placed on the ground, in tree cavities, on stumps, and on small cliff ledges, generally within five meters of water. Clutch size averages five eggs. Male leaves the breeding grounds during incubation. Female incubates for approximately 28 days. Young are able to feed on their own within a day or two of hatching. Female typically remains with brood until migration (Robertson and Goudie 1999).
In Montana, no males have been reported on breeding streams prior to attaining adult plumage at 3-years of age (Phillips 1986, Reichel and Genter 1996). The youngest female known to have bred is a single 2-year-old (Reichel and Genter 1996).
In Montana during 1989 to 1994, annual numbers of ducklings fledged per adult female averaged 1.60 and ranged from 0.84 to 3.15 (n=230 adult females; Reichel and Genter 1995).
The proportion of females successfully raising a brood varies widely between years. In Montana, 230 females observed between 1989 and 1994 raised 103 broods for an average of 44.8% and ranged from 24% to 55% (Reichel and Genter 1995). High summer runoff has been associated with low productivity (Kuchel 1977, Diamond and Finnegan 1992, 1993, Reichel and Genter 1993, 1995).
Management
The Harlequin Duck is listed as a Sensitive Species by the U.S. Forest Service and the Bureau of Land Management. In 2014, the first systematic statewide survey of known or likely brood streams for this species in Montana detected a total of 31 broods with 126 chicks. It is uncertain how these reproductive levels compare with previous surveys; however, Harlequin Duck reproduction was not detected in a large number of previously documented brood streams. Spring warming of 2014 occurred later than average and that, accompanied by a high snowpack, may have affected the suitability of some streams for breeding.
Stewardship Responsibility
Threats or Limiting Factors
Logging of mature forests likely has a detrimental impact to breeding habitat, not only influencing the availability of nest sites, but also impacting stream sedimentation, temperature, flow, and food availability. Additionally, mining activity and hydroelectric dams also pose a threat. This species is also sensitive to human disturbance, particularly if the disturbance is frequent and/or heavy (Robertson and Goudie 1999). Hunting has also been implicated in the decline of some populations.
References
- Literature Cited AboveLegend:
View Online Publication
Ashley, J. 1994. 1992-93 harlequin duck monitoring and inventory in Glacier National Park, Montana. Unpublished report. Division of Research Management, Glacier Natl. Park, Montana. 57 pp.- Ashley, J. 1994. Progress report: harlequin duck inventory and monitoring in Glacier National Park, Montana. Unpublished report. Division of Research Management, Glacier Natl. Park, Montana. 14 pp.
- Ashley, J. 1995. Harlequin duck surveys and tracking in Glacier National Park, Montana. Unpublished report. Division of Natural Resources, Glacier National Park, West Glacier, Montana. 41 pp.
- Bent, A.C. 1925. Life histories of North American wild fowl. Order: Anseres (Part II). U.S. National Museum Bulletin 130. Washington, D.C. 316 pp.
- Diamond, S. and P. Finnegan. 1992. Harlequin duck ecology on Montana's Rocky Mountain Front. Unpublished report. Rocky Mountain District, Lewis & Clark National Forest, Choteau, MT. 45 pp.
- Diamond, S. and P. Finnegan. 1993. Harlequin duck ecology on Montana's Rocky Mountain Front. Unpublished report. Rocky Mountain District, Lewis & Clark National Forest, Choteau, MT. 45 pp.
- Fairman, L. and G. Miller. 1990. Results of the 1990 survey for harlequin ducks (Histrionicus histrionicus) on the Kootenai National Forest, Montana and parts of the Lolo National Forest, Montana. Helena, MT: Montana Natural Heritage Program. 43 p.
- Jewett, S. G. 1931. Nesting of the Pacific harlequin duck in Oregon. Condor 33:255.
- Kuchel, C. R. 1977. Some aspects of the behavior and ecology of harlequin ducks breeding in Glacier National Park, Montana. M.S. thesis. University of Montana, Missoula. 160 pp.
- Marks, J.S., P. Hendricks, and D. Casey. 2016. Birds of Montana. Arrington, VA. Buteo Books. 659 pages.
- Phillips, J. C. 1986. A natural history of the ducks, vol. III. Dover Publications, Inc., NY. 383 pp.
- Reichel, J.D. and D.L. Genter. 1993. Harlequin duck surveys in western Montana: 1992. Montana Natural Heritage Program, Helena, MT. 67 pp., including appendices and maps.
- Reichel, J.D. and D.L. Genter. 1994. Harlequin duck surveys in western Montana: 1993. Montana Natural Heritage Program, Helena, MT. 87 pp.
- Reichel, J.D. and D.L. Genter. 1995. Harlequin Duck surveys in western Montana: 1994. Montana Natural Heritage Program. 58 pp.
- Reichel, J.D. and D.L. Genter. 1996. Harlequin duck surveys in western Montana: 1995. Montana Natural Heritage Program, Helena, MT. vii + 107 pp.
- Robertson, G. J., and R. I. Goudie. 1999. Harlequin Duck (Histrionicus histrionicus). In The birds of North America, No. 466 (A. Poole and F. Gill, Eds.). Academy of Natural Sciences of Philadelphia and American Ornithologists’ Union.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- [WWPC] Washington Water Power Company. 1995. 1994 wildlife report Noxon Rapids and Cabinet Gorge Reservoirs. Washington Water Power Company. Spokane, WA.
- American Ornithologists’ Union [AOU]. 1998. Check-list of North American birds, 7th edition. American Ornithologists’ Union, Washington, D.C. 829 p.
- Ashley, J. 1994. Status of Harlequin ducks in Glacier National Park, Montana. P. 2 in: Proc. 2nd ann. Harlequin duck symposium, March 13-15, 1994. Harlequin Duck Working Group. 22 pp. plus appendices.
- Ashley, J. 1996. Harlequin duck inventory and monitoring in Glacier National Park, Montana. Unpublished report. Division of Natural Resources, Glacier National Park, West Glacier, Montana. 21 pp.
- Ashley, J. 1997. Harlequin Duck inventory and monitoring in Glacier Natioanal Park, Montana. Unpublished (draft)report. Division of Natural Resources, Glacier National Park. West Glacier, Montana. 36 pp.
- Ashley, John. 1998. Harlequin Duck use on the Middle Fork of the Flathead River in the vicinity of the Essex bridge. MDOT Project BR 1-2(85)180/Control number 1763.
- Atkinson, E. C. 1991. Distribution and status of harlequin ducks and common loons on the Targhee National Forest. Idaho Dep. of Fish and Game, Nongame and endangered wildlife prog. 27 pp.
- Atkinson, E.C. 1991. Distribution and status of Harlequin ducks (Histrionicus histrionicus) and common loons (Gavia immer) on the Targhee National Forest. Cooperative Challenge Cost Share Project Report. Targhee National Forest and Idaho Dept. of Fish and Game. 43 p.
- Atkinson, E.C. and M.L. Atkinson. 1990. Distribution and status of harlequin ducks (Histrionicus histrionicus) on the Targhee National Forest. Cooperative Challenge Cost Share Project. Boise, ID: Idaho Dept. of Fish and Game, Nongame and Endangered Wildlife Program. 25 p.
- Atkinson, E.G. 1991. Distribution of harlequin ducks ( Histrionicus histrionicus ) and common loons (Gavia immer) on the Targee National Forest. Coop. Challenge Cost Share Proj. Targee Natl. For. and Id. Dept. Fish Game.
- Bailey, V. and F.M. Bailey. 1918. Wild animals of Glacier National Park: the mammals, with notes on physiography and life zones, and the birds. U.S. Department of the Interior, National Park Service. 210 p.
- Bate, L.J. 2010. Harlequin Duck surveys along upper McDonald Creek Glacier National Park. Division of Science and Resource Management Glacier National Park. 11pp.
- Bellrose, F.C. 1978. Harlequin duck. pp. 380-384. In: Ducks, geese, and swans of North America. Harrisburg, PA: Wildlife Management Institute, Stockpole Books. 540 p.
- Bengtson, S.A. 1972. Breeding ecology of the harlequin duck (Histrionicus histrionicus) in Iceland. Ornis Scandinavica 3:1-19.
- Bengtson, S.A. and S. Ulfstrand. 1971. Food resources and breeding frequency of the harlequin duck Histrionicus histrionicus in Iceland. Oikos 22:235-239.
- Bengtson, S-A. 1966. Field studies on the harlequin duck in Iceland. Wildfowl Trust Ann. Rep. 17:79-84.
- Bent, A. C. 1962. Life histories of North American wild fowl. Part II. New York, NY: Dover Publications. 865 p.
- Boyd, D. 1994. Conservation of harlequin ducks (Histrionicus histrionicus). Missoula, MT: University of Montana School of Forestry. 14 p.
- Breault, A. M. 1993. Harlequin duck status report 1992: British Columbia. Pp. 60-64 in: Cassirer, E. F., et al., (eds.), Status of Harlequin ducks in North America. Harlequin Duck Working Group. 83 pp.
- Breault, A. M. and J.-P. L. Savard. 1991. Status report on the distribution and ecology of Harlequin Ducks in British Columbia. Can Wildlife Service, Pacific and Yukon Region, Tech. Rep. Series 110. 108 pp.
- Brown, M. E. 1998. Population genetic structure, kinship, and social associations in three Harlequin Duck {Histrionicus histrionicus) breeding subpopulations. M.S. Thesis, University of California, Davis. 104 pp.
- Burleigh, T. D. 1952. Spring migration. Audubon Field Notes 6:258-260, 291, 292.
- Burleigh, T.D. 1951. Spring migration. Audubon Field Notes 5:266-268.
- Burleigh, T.D. 1972. Birds of Idaho. The Caxton Printers, Ltd., Caldwell, ID. 467 pp.
- Byrd, G. V., J. C. Williams, and A. Durand. 1992. The status of Harlequin ducks in the Aleutian Islands, Alaska. Pp. 14-22 in: Proc. Harlequin Duck Symposium, April 23-24, 1992, Moscow, Idaho. ID Dept. of Fish & Game, U.S. For. Serv. Intermountain Research Station, ID Panhandle Nat. Forests, and Northwest Section of Wildlife Society. 46 pp.
- Campbell, R.W., N.K. Dawe, I. McTaggart - Cowan, J.M. Cooper, G. Kaiser, and M.C.E. McNall. 1990. The birds of British Columbia. Vol. 1. Nonpasserines: introduction and loons through waterfowl. R. B.C. Mus., Victoria.
- Carlson, J. C. 1990. Results of 1990 surveys for harlequin ducks on the Flathead National Forest, Montana. UnpubI. Rep., USDA Forest Service. 31 pp.
- Carlson, J.C. 1990. Results of harlequin duck (Histrionicus histrionicus) surveys in 1990 on the Flathead National Forest, Montana. Unpublished report to the USDA Forest Service, Cooperative Challenge Cost Share Program. 31 p.
- Casey, D. 2000. Partners in Flight Draft Bird Conservation Plan Montana. Version 1.0. 287 pp.
- Cassirer, E. F. 1993. Harlequin duck status report 1992: Idaho. pp. 27-30 In: Cassirer, E. F., et al., eds. Status of Harlequin ducks in North America. 83 pp.
- Cassirer, E. F. and C. R. Groves. 1994. Breeding ecology of Harlequin ducks in Idaho. P. 3 in: Proc. 2nd ann. Harlequin duck symposium, March 13-15, 1994. Harlequin Duck Working Group. 22 pp. plus appendices.
- Cassirer, E.F. 1989. Distribution and status of Harlequin ducks (Histrionicus histrionicus) on the Nez Perce National Forest, Idaho. Report on Challenge Cost Share Project. 13 pp.
- Cassirer, E.F. 1994. Proposed inventory and monitoring protocol for harlequin ducks in northern Idaho. Interagency Rare Animal Workshop. March 2, 1994. Post Falls, ID. 14 p.
- Cassirer, E.F. 1995. Harlequin duck monitoring in northern Idaho, 1995. Cooperative project report. Idaho Department of Fish & Game, North Idaho Traditional Bowhunters, U.S. Forest Service, and Washington Department of Fish and Wildlife. 20 p.
- Cassirer, E.F. 1995. Harlequin duck monitoring on the Moyie River and other tributaries to the Kootenai River in northern Idaho subsequent to natural gas pipeline construction. [Unpublished report]. Lewiston, ID:Idaho Department of Fish and Game. 11 p.
- Cassirer, E.F. and C.R. Groves. 1989. Breeding ecology of harlequin ducks (Histrionicus histrionicus) on the Kaniksu National Forest, Idaho. Report on Challenge Cost Share Project. 48 p.
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- Cassirer, E.F. and C.R. Groves. 1990. Distribution, habitat use and status of harlequin ducks (Histrionicus histrionicus) in northern Idaho, 1990. Cooperative Challenge cost Share Project. Boise, ID: ID Dept. of Fish and Game, Nongame and Endangered Wildllife. 54 p.
- Cassirer, E.F. and C.R. Groves. 1990. Distribution, habitat use, and status of hariequin ducks in northern Idaho, 1990. Idaho Dept. Fish Game, Nongame Endangered Wildl. Prog. 54 pp.
- Cassirer, E.F. and C.R. Groves. 1991. Harlequin duck ecology in Idaho: 1987-1990. Boise, ID: Idaho Dept. of Fish and Game. 93 p.
- Cassirer, E.F. and C.R. Groves. 1992. Ecology of Harlequin Ducks in northern Idaho; progress report 1991. Boise, ID: Idaho Dept. of Fish and Game. 74 p.
- Cassirer, E.F. and C.R. Groves. 1992. Status and Ecology of Harlequin Ducks in Idaho. In Proceedings, Harlequin Duck Symposium, April 23-24, 1992. Rep., 45pp. Idaho Dept. Fish and Game, Moscow, ID.
- Cassirer, E.F. and C.R. Groves. 1994. Ecology of harlequin ducks (Histrionicus histrionicus) in Northern Idaho. Study No. 4202-1-7-2. Boise, ID: Idaho Department of Fish and Game. 51 p.
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- Clarkson, P. 1994. Managing watersheds for harlequin ducks. Unpublished presentation. American River Management Society River Without Boundaries Symposium, Grand Junction, CO. 33 pp.
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- Cooke, F., G. J. Robertson, R. I. Goudie and W. S. Boyd. 1997. Molt and the basic plumage of male Harlequin Ducks. Condor 99:83-90.
- Cottam, Clarence. 1939. Food habits of North American diving ducks. USDA Tech. Bull. No. 643:81-86.
- Coudie. R. I. 1984. Comparative ecology of Common eiders, black scoters, oldsquaws and harlequin ducks wintering in southeast Newfoundland. Thesis. Univ. of W. Ontario. London, Ontario. Canada.
- Crowley, D. W. 1994. Breeding habitat of Harlequin ducks in Prince William Sound, Alaska. P. 4 in: Proc. 2nd ann. Harlequin duck symposium, March 13-15, 1994. Harlequin Duck Working Group. 22 pp. plus appendices.
- Davis, C.V. 1961. A distributional study of the birds of Montana. Ph.D. Dissertation. Corvallis, OR: Oregon State University. 462 p.
- Devlin, S. Wildlife biologists can't get enough of the elusive harlequin duck. Missoula, MT: Missoulian. 23 May 1991. p. 1C.
- Diamond. Seth. 1990. [Various reports of harlequin sightings along the RMF during 1990.]
- Dzinbal, K. A. 1982. Ecology of Harlequin ducks in Prince William Sound, Alaska, during summer. M.S. thesis. Ore. State Univ., Corvallis. 89 pp.
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