Reproduction 



Harlequins were present this year on at least 12 streams in the study area and adult 

 females or broods were seen on 1 1 of those streams. A minimum of 43 adult females were 

 present. Late- July to early- August brood size on all streams averaged 2.81 (n=21). This was 

 lower than in 1992 (3.27). Brood size did not vary between the North Fork Flathead and Lower 

 Clark Fork drainages in 1993. Most broods were seen in Class HI or fledged stages of 

 development (Bellrose 1976:27), and we made no adjustment for age of broods in our calculation 

 of mean brood size. 



Of 37 potential broods on North Fork of the Flathead and lower Clark Fork drainages, a 

 minimum of 16 were produced for a 43% success rate of broods per adult female. From 1989 to 

 1993 (Table 4), the success rate averaged 46.5% (range= 24-55%; n=200 pairs on 35 streams). 

 In 1993, the differences in success rates between the North Fork Flathead drainage (32%) and the 

 Lower Clark Fork drainage (60%) were large. Annual differences in success rates from 1989- 

 1992 were primarily associated with the amount and timing of runofif. High runofi^ particularly in 

 June-early July, and runoff in years with "double peaks" caused lower reproductive success. This 

 was particularly evident in 1991 (Table 4, Figure 2, 3) the only year where runoff exceeded 

 20,000 cfs and when production was lowest (24%). The changes in reproductive success were 

 primarily due to changes in numbers of broods per pair, not changes in the size of successful 

 broods. This indicates that differences in mortality were due to events that affected entire 

 clutches or very young broods. 



13 



