Life history and habitat use 



Wintering and nonbreeding ecology 



Harlequin ducks winter along northern coastlines, usually near reefs, rocky islands, and 

 cobble beaches. Coastal numbers are greatest from October through March or April (Campbell et al. 

 1990, Byrd et al. 1992), although nonbreeding and immature individuals may remain on the ocean 

 year-round. Pair bonds are likely formed in coastal areas. Banding efforts suggest that individuals 

 exhibit fidelity to both molting and wintering areas (Goudie, Breault, unpubl. data, pers. comm). 



Distribution of harlequin ducks along the coast shifts within and among years (Schirato and 

 Sharpe 1992), partially due to food availability (Chadwick 1992). Marine foods include crustaceans, 

 gastropods, and other invertebrates (Vermeer 1983, Goudie and Ankney 1986, Gaines and Fitzner 

 1987), and roe (Vermeer 1983, Chadwick 1992). 



Sex ratios on wintering areas are biased towards males in most areas (British Columbia 60% 

 males, 40% females or apparent females, Campbell et al. 1990, Chadwick 1992; Amchitka and 

 Shemya Islands, Alaska 53-56% males, Byrd et al. 1992). Summering ratios of males in some areas of 

 coastal British Columbia increase to 95% (Campbell et al. 1990). However, in some areas females and 

 juveniles predominate (Adak Island, Alaska 46% males, Byrd et al. 1992; Maine 48% males, 52% 

 apparent females, Mittelhauser 1991). 



Mi gration 



Harlequin ducks migrate from the coast to breeding areas from March through June and return 

 to the coast from June through September. Little is known about migration routes, although they are 

 thought to follow stream corridors, particularly where breeding streams are relatively close to coastal 

 wintering sites (Bengtson 1966, Dzinbal 1982). Birds evidently fly to Rocky Mountain breeding areas 

 east of the continental divide. Migration to these areas probably involves a combination of swimming 

 and flight, and may be influenced by distance from wintering areas, as well as weather and snow 

 conditions encountered enroute. There appear to be some locations along travel corridors in the Rocky 

 Mountains where harlequin ducks stop regularly during spring migration. Few birds are observed 

 during return migration to the coast in summer and fall, therefore this migration is thought to be 

 relatively rapis (Wallen 1987, 1991). 



Harlequin ducks marked on breeding streams in northern Idaho (4 ducks), northwestern 

 Montana (12 ducks), and northwestern Wyoming (2 ducks) have been reobserved along Oregon, 

 northwestern Washington, and southern British Columbia coastlines July - March (Wallen 1991, 

 unpubl. data; Cassirer and Groves 1992, 1994, unpubl. data; Reichel and Genter 1994, 1995, unpubl. 

 data). 



Breeding ecology 



Both pairs and bachelor drakes migrate to breeding areas. Unpaired hens are uncommon on 

 the breeding grounds during spring. Spring sex ratios on breeding streams average 55-64% males 

 (Bengtson 1972, Kuchel 1977, Inglis et al. 1989). Harlequin ducks maintain a multi-year pair bond, 

 and both pairs and bachelor drakes exhibit strong fidelity to breeding streams (Kuchel 1977, Wallen 

 1987, Cassirer and Groves 1991, Reichel and Genter 1995). 



