Four nests of Mergus squamatus were located in two breeding seasons (from April to May), 2005 and 2006 at Dailing Bishui Nature Reserve, Heilongjiang Province. We measured the characteristics of the nests and made observation on the breeding and hatching behaviors for the 4 pair birds. M.squamatus arrived in the breeding area in late March and early April and left for winter area in one month from late September to late October. They spent about 210 days in their breeding area. The four nests were built in aged trees of elms (Ulmus propinqua) and poplars (Populus ussuriensis) that located in a quite open sites near river and road. The distances between two nests ranged from 1.6 km to 10 km. Copulation was made in water, females took 85.3% and 14.7% of their activity time to hatch and feed, respectively. While males spent 24.4% of their activity time to feed and they neither involved in hatching nor in feeding ducklings.