Onset of broodiness and incubation in relation to laying. Incubation starts prior to 

 completion of the clutch (Bengtson 1966). 



Incubation period Thompson et al. (1993) reported one nest which took at least 37 days (3 

 June- 10 July) and another which took at least 24 days (10 May to 3-10 June). Bengtson (1972) 

 found an average incubation period (laying of last egg to hatching of last egg) of 28 days (n=4, 

 range 27-29) in Iceland. 



Parental behavior. 



Roles and attention to eggs and incubating mate. Only females incubate eggs (Bengtson 

 1966). 



Incubation rhythm, duration of attentive periods. Bengtson ( 1 966) reported on a female 

 who was away form the nest for about 2 hrs. He felt that females only fed about once every 48 

 hrs. 



DEMOGRAPHY AND POPULATIONS 



MEASURES OF BREEDING ACTIVITY 



Age at first breeding; intervals between breeding Very few 2-year-old males have been 

 reported on the breeding grounds in North America. Yeariing males make up 1-2% of the 

 population on the breeding grounds in Iceland (Bengtson 1972, Gardarsson 1979). In Montana, 

 no males have been reported on breeding streams prior to attaining fully adult plumage at 3 -years- 

 old (Phillips 1925, Reichel and Genter 1996). 



The youngest female known to have bred is a single 2-year-old, although nine additional non- 

 breeding 2-year-olds have been observed on natal streams and thirteen marked 2-year-olds are 

 known to have been alive (Reichel and Genter 1996). 



Some females on breeding streams apparently do not lay eggs (Bengtson and Ulfstrand 1971, 

 Dzinbal 1982, Wallen 1987, Cassirer and Groves 1991). Bengtson and Ulfstrand (1971) classified 

 15-30% (n=48) of adult (by bursae inspection) females as non-breeders, and found that 87% of all 

 clutches were successful; therefore, approximately 90% of non-breeding females did not even 

 attempt to breed in Iceland. Additionally, examination of ovaries of 6 non-breeding females 

 showed that none had lain eggs (Bengtson and Ulfstrand 1971). Many of these non-breeding 

 "adults" may have been young (2-3 year-old) birds since cloacal examination gives aduh status to 

 2-year-olds. However, in Iceland, Bengtson (1966) believed that 2-year-old females Hadequins 

 did not regularly go to the breeding grounds. Dzinbal (1982) estimated that 53-95% of females 

 not producing broods did not attempt to breed; those resuhs may have been due to use of patagial 

 markers negatively affecting breeding behavior (Bustnes and Erikstad 1990) Wallen (1987) 

 reported that some females left the breeding stream at the same time as their mates, unpaired 

 females arrived about 4 weeks later than pairs, did not breed, and left after 3-5 weeks. 



Clutch size Twelve clutches from the Pacific Northwest averaged 6.25 eggs (range 3-7) and 

 are listed below. In Montana, a clutch of 5 was reported (Diamond and Finnegan 1993), four 

 clutches of 6, 6, 7, and 7 were reported in British Columbia (Campbell et al. 1990), and 2 clutches 

 of 7 in Washington (Jewett et al. 1953). Cassirer et al. (1993) reported on 3 nests with 3, 5, and 

 7 eggs in Idaho. Thompson et al. (1993) reported 2 nests, each with 7 eggs, in Oregon, while 

 Gabrielson and Jewett (1940) reported a clutch of 6 eggs on 30 May 193 1 on the Salmon River 

 near Zigzag. In Iceland, 77 complete clutches averaged 5.7 eggs with a range of 3-9 (Bengtson 



12 



