Breeding chronology tends to be delayed in areas with later snowmelt: harlequin ducks in the 

 northern Columbia Basin breed approximately 2 weeks earlier than in the higher elevation 

 Intermountain area (Wallen 1987, Cassirer and Groves 1990). Egg laying and incubation generally 

 occur during May and June. At the start of incubation, the drakes return to the coast, eliminating the 

 possibility of renesting. During late June and early July nonbreeding, possibly immature, hens appear 

 on the streams and remain until after hatching occurs in June and July. Nonbreeding and unsuccessful 

 hens migrate to the coast in July. Successful hens remain on the streams with the ducklings, although 

 up to 40% abandon their broods before fledging (Wallen 1987, Cassirer and Groves 1991). Ducklings 

 return to the coast in the summer and fall after fledging. Males do not attain full breeding plumage 

 until after their second winter and in general harlequin ducks do not breed until after their first year. 



Breeding habitat 



The harlequin is the only duck in the northern hemisphere to breed almost exclusively along 

 swiftly flowing mountain streams. Within their breeding range, harlequin ducks nest only along a 

 select number of clear streams with rocky substrates. Stream channels range from braided to straight, 

 with an abundance of riffle and rapid habitats. Some use of mountain lakes and lake outlets has been 

 documented in the Canadian Rockies (Clarkson 1992), Montana (Ashley 1994, Reichel and Genter, 

 unpubl. data) and Iceland (Bengtson 1972). Bank vegetation is highly variable, from moorland in 

 Iceland, spruce forest and willow thickets in Labrador, willow shrub or pole or immature-sized 

 lodgepole pine (Pinus contorta), Engelmann spruce (Picea engelmanii), and Douglas-fir (Pseudotsuga 

 menziesii) forest in Wyoming, Montana, and southern Idaho (Wallen 1987, Atkinson and Atkinson 

 1990, Diamond and Finnegan 1993), to mature or old-growth western redcedar (Thuja plicata) - 

 western hemlock (Tsuga heterophylla) in the Pacific northwest (Cassirer and Groves 1991). 



Harlequin ducks usually nest close to streams on streambanks or islands, but nesting habits are 

 highly variable. Nests may be on the ground in dense vegetation, in rocky cavities, piles of woody 

 debris, undercut streambanks, or in cliff cavities above the stream, or hollow trees or snags in the 

 adjacent forest. Nests are extremely well-hidden, and are often, although not always, upstream of pair 

 activity areas (Bengtson 1972, Cassirer et al. 1993). 



Gradient, water quality, substrate, and bank vegetation are useful indicators of potential 

 harlequin duck breeding habitat. The following characteristics are typical of harlequin duck breeding 

 streams in the Rocky Mountains: 



1 . Stream size second-order or greater. 



2. Reaches on the stream with average gradient between 1 % and 7%, with some areas of shallow 

 water (riffles). 



3. Clear water. 



4. Rocky, gravel to boulder-size substrate. 



5. Forested bank vegetation. 



Some factors that may increase likelihood of use by harlequin ducks include: 



1 . Proximity to occupied habitat 



2. Hiding cover along the stream; including overhanging shrub vegetation, logjams, undercut 

 streambanks, woody debris and instream loafing sites (boulders or gravel bars adjacent to 



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