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We recorded molt patterns of migrant Northern Saw-whet Owls (Aegolius acadicus) at three locations in the Great Lakes region: Stevens Point, Wisconsin; Whitefish Point, Michigan; and Duluth, Minnesota. We then analyzed the molt patterns of recaptured birds that were banded in a previous season and originally classified as hatch-year birds (i.e., they had no remigial molt). Of these 286 known-age birds included in our analysis, 155 (54%) were second-year (SY), 72 (25%) were third-year (TY), 39 (14%) were fourth-year (4Y), 16 (6%) were fifth-year (5Y), three (1%) were sixth-year (6Y), and one (0.30%) was eighth-year (8Y). Using these known-age birds, we were able to identify definitive molt patterns for the SY and TY age classes. All 155 (100%) SY birds and 52 (72%) of the TY birds matched our ageing criteria. The remaining 28% of TY birds did not match our ageing criteria and were classified as after-second-year (ASY). Of the entire sample (n = 286), only three birds (1%) matched an incorrect age class, including one 4Y that matched the SY age class and two 5Y that matched the TY age class. [ABSTRACT FROM AUTHOR]

The article discusses the time duration and intensity of feather shedding or molt in tropical birds of Savanna in Brazil. It states that when compared with temperate zone birds, tropical birds have slower metabolism and have molt duration of 122 days and intensity 3.1 feathers growing simultaneously. It is informed that the larger species take more time to molt than the smaller ones.