1972). There was a seasonal decline in clutch size (Bengtson 1972). The mean number of eggs 

 to hatch from successful nests was 5.3 (Bengtson 1972). A single known Greenland clutch was 8 

 (Salomonsen 1950). 



Annual and lifetime reproductive success In Montana during 1989-1994, annual numbers 

 of ducklings fledged per aduh female averaged 1.60 and ranged from 0.84 - 3.15 (n=230 adult 

 females) (Reichel and Center 1995), Brood size of Class I-lIb young (Bellrose 1976) averaged 



5.1 on the Rocky Mountain Front (Diamond and Finnegan 1993), while throughout Montana, size 

 lie to fledging averaged 3.57 and ranged from 2.81 - 5.86 (n=103 broods) (Diamond and 

 Finnegan 1993, Reichel and Center 1995). Average brood size at fledging in Clacier National 

 Park during 1973-75 ranged from 2 to 4.25 (n=8), while numbers of young fledged per adult 

 female ranged from 0.1-1.3 (Kuchel 1977:72-73). 



Broods ranged from 1-6 in Oregon and averaged 2.7 (n=26) (Thompson et al. 1993, 1994). 

 These sightings, however, were spread throughout the breeding season and therefore should not 

 be considered the same as numbers fledged. 



In Idaho, number of ducklings fledged per aduh female ranged from 0.7 - 1.3 and averaged 



1.2 (n=14); number of females producing broods was 29% in 1990 (Cassirer and Croves 1991, 

 1994). Average brood size was 3.4 (range 1-7) in Idaho (n=24) (Cassirer and Croves 1991). 



In British Columbia, 41 broods of all ages ranged in size from 1-10 (1 Y-3, 2Y-3, 3Y-5, 4Y- 

 1 1, 5Y-14, 6Y-2, 7Y-1, 8Y-1, lOY-1); the brood with 10 young was apparently from a single 

 female (Campbell et al. 1990). 



In Alaska, numbers of young per breeding female and per adult female were respectively 1.5 

 and 0.8 in 1979, and 0.6 and 0.3 in 1980, patagial tags on adults $$ appeared to have caused poor 

 reproductive success (Dzinbal 1982). 

 Non-breeding frequency of females was 47% in 1979 and 50% in 1980 (Dzinbal 1982). 



In Iceland, 1.73 (85:49) and 2.43 (120:49) young per aduh female were successfully raised 

 respectively during 1975 and 1976 (Cardarsson 1979). In an increasing population in Iceland, 

 productivity ranged from 0. 1 to 3 .3 (x = 1 . 1 ) ducklings fledged per hen per year over 1 5 years 

 (Cardarsson and Einarsson 1991). This was similar to that found by Bengtson (1972) who 

 reported 0.0 to 3.8 young per adult female on 4 rivers during 4 years. 



Proportion of total females that rear at least one brood to nest-leaving The proportion of 

 females successfully raising a brood in a single year, varies widely between years. Reported 

 numbers range from 12-56% (Bengtson and Ulfstrand 1971, Kuchel 1977, Wallen 1987, Cassirer 

 and Croves 1991, Reichel and Center 1995). In Montana, 230 females observed between 1989 

 and 1994 raised 103 broods for an average of 44.8% (range 24-55%) (Reichel and Center 1995). 



Sex ratio. Cassirer (1995) found a spring aduh sex ratio of 1 .3 1 : 1 (m:f n = 8 1 ) in 1995 on 

 Idaho streams. In Banff National Park, Alberta, sex rations varied from 1.37:1 in May to 1.81 in 

 June (Smith 1996). In Iceland, sex rations on the breeding grounds varied from 54-70% males 

 during 5 summers in late May - early June (Bengtson 1966, Bengtson 1972, Cardarsson 1979). 



In coastal British Columbia the apparent sex ratio is 1.5:1 (544 birds) in winter declining to 

 1 .4: 1 (297 birds) in March- April (Campbell et al. 1990); this grows to 4.3: 1 in May and by July, 

 when aduh females are still on the breeding streams, it reaches 18.2: 1 (1633 birds). 



LIFE SPAN AND SURVIVORSHIP 



13 



