Body weight and feather growth of male Barrow's Goldeneye during wing molt

We studied the timing. duration, and rate of wing molt of male Barrow's Gol deneye (Bucephala islandica). The mean daily change in primary feather leng th was 2.6%. which is consistent with rates reported for other waterfowl sp ecies. The mean length of the flightless period was 31 days (range: 27-34 d ays), excluding the pre-shedding interval. Wing molt extended from early Ju ly to mid-September. Peak wing molt occurred between 20 July and 23 August. The mean body weight of adult males decreased significantly during wing mo lt. Heavier birds had greater remigial growth rates and experienced more su bstantial declines in body weight than lighter birds, suggesting that body reserves may be used to increase the rate of remigial growth.