densities per km surveyed including juveniles ranged from 0.07 to 2.37 (Thompson et al. 1993, 

 1994). 



On the Bow River in Banff National Park, densities observed were the highest known 

 from streams in North America, ranging from 2.4 ducks/km on a 1 5 km reach to 6.2 on a 1 6 km 

 reach (Smith 1996). 



On Kodiak Island, Alaska, density of breeding Harlequin pairs ranged from 0.63 pairs/km 

 along the Ayakulik River to 1.98-7.24 birds/km in 3 coastal bays (Zwiefelhofer 1994). Dzinbal 

 (1982) reported 1.3-1.8 pairs/km on two small coastal streams in Alaska. 



On the Laxa River in Iceland, Harlequins are apparently present at densities higher than 

 other known stream populations (Bengtson 1972). Twenty populations in Iceland ranged from 

 0.2 to 8.5 pairs/km, with an average of 0.9 pairs/km (Bengtson and Ulfstrand 1971, Bengtson 

 1972). 



In eastern Siberia, Kistschinsky (1968 in Bengtson 1972) found 1.1 pairs/km and 0.8 - 1.2 

 broods/km. 



Numbers. Numbers estimated by most recent publications and reports are listed in Table 

 8. Cassirer et al. (1996) reported that the maximum percentage of pairs observed during surveys 

 done under optimal conditions was 69%. This is similar to the 75% (range 67-81%) reported by 

 Ashley (pers. comm.) on McDonald Creek during 1993-1996. Estimated pair numbers for 

 Montana (Table 8) were calculated using 72%. However, that percentage was not used to adjust 

 minimum numbers on streams when a high proportion of ducks were individually marked and 

 multiple surveys took place in several years; in those cases 90% was used. A minimum of 1 5 1 

 pairs of ducks nest in Montana, which represents an estimated 198 total pairs (Table 8, Appendix 



F). 



The largest single reported Harlequin Duck occurrence (see Breeding Range) is from the 



Bow River drainage in Banff National Park, Alberta, where, using a mark/resight model, 215 



individuals were calculated to occur during 1995 (Smith 1996). 



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