In the 2010/2011 winter, Birds Korea conducted research on the distribution and habitat use of Scaly-sided Merganser on two rivers in the southeast of the ROK. This research recorded a peak count of 56 Scaly-sided Merganser on one main river and 9 on the second river. We started this winter’s Scaly-sided Merganser research on November 6. We counted 26 Scaly-sided Merganser on the main river, including 13 males and 13 ‘redheads’. On November 20, 23 Scaly-sided Mergansers were observed, including 12 males and 11 ‘redheads’. We would appreciate hearing from experienced observers on ways to determine with confidence the age and sex of First Calendar Years.