Gardarsson and Einarsson 1993 in Gislason 1994). 



Other Concentrated Harlequin Duck use occurs on several stream reaches in Montana 

 believed to share certain hydrologic characteristics; in particular, stream reaches supporting 

 notable breeding success are observed to receive locally high rates of groundwater discharge 

 (Reichel and Center 1996). This has also been noted in British Columbia (Clarkson 1992, Hunt 

 1993). Some of the densest known Harlequin breeding populations occur in Iceland on the River 

 Laxa which is the outlet of Lake Myvatn; this lake is spring fed, resulting in very stable flows, 

 with almost no flooding (Bengtson and Ulfstrand 1971, Gardarsson et al. 1988). Groundwater 

 discharge may influence Harlequin success by affecting flow regimes, thermal characteristics, 

 geochemistry and nutrient status, macroinvertebrate fauna, or a interaction of these factors. 



WINTER (NON-BREEDING) RANGE 



In Iceland, birds primarily use rocky areas with breaking surf (Bengtsonl966). In British 

 Columbia, they are found in often turbulent waters near rocky islets, shores, and bays where they 

 fi"equently feed in kelp beds (Campbell et al. 1990). 



BREEDING 



PHENOLOGY 



Pair formation Pair formation in Washington took place on the wintering grounds beginning 

 in October and was completed by early February (Fleischner 1983). In Iceland, about 10% of 

 birds were paired by December (Bengtson 1 966). Copulation occasionally takes place on the 

 British Columbia coast in early April (Pearse 1945). 



Nest building. In Iceland, females begin looking for a nest site 1 -2 weeks prior to egg laying 

 (Bengtson 1966). 



Egg laying In Montana, egg laying takes place between 30 April and 4 July, with most 

 occurring between 10 May and 10 June (Kuchel 1977, Reichel and Genter, unpubl. data). Dates 

 on which clutches have been found in British Columbia range from 24 May to 24 June; 

 backdating indicated that the earliest clutch was laid on 17 May (Campbell et al. 1990). Egg 

 laying in Iceland takes place between 10 May and 8 July, with most occurring in early June 

 (Bengtson 1966). 



Hatching Thompson et al. (1993) reported hatching at two nests on 2-10 June and 10 July. 

 Kuchel (1977) estimated hatching dates for broods on McDonald Creek, Glacier National Park: 

 13 of 15 occurred between 27 June and 7 July with the extremes on 1 1 June and 2 August. In 

 Iceland, young begin to appear in early July (Bengtson 1966). Dates of all ages of brood records 

 in British Columbia range from 16 June to 13 September, with 53% between 10 July and 12 

 August (Campbell et al. 1990). 



Postbreeding. Young in Montana fledged between 1 5 July and 1 September, with most 

 fledging between 25 July and 15 August (Kuchel 1977, Reichel and Genter, unpubl. data). 



NEST SITE 



Few nests have been located in the Pacific population; two nests were on rocks, six were on 

 the ground, two were on cliff faces, two were in piles of woody debris adjacent to streams, two 

 were in tree cavities, and one was in a cavity on a cliff face. In Montana, a nest was found on a 



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