The Common Merganser or Goosander is among the largest of the sawbill group, with males weighing up to 4.5 lbs. These large fish-eaters have long bills with serrated edges, which enables them to grip their prey. In captivity they will need extra protein added to their diet, this can be easily done by mixing in catfish or trout pellets into their feed.
Male Commons do not acquire their dark green head until their second year. The male Common does not have a large crest, and the crest of the female is often larger than the males.
Though not considered an aggressive species because of their large size, care should be taken when mixing them with other smaller species. My Commons have at times harassed my Smew, and other smaller ducks, however to date I have not had any injuries.
Commons are a northern bird and may have trouble adapting to summers in warm climates. Plenty of shade should be provided, and water kept as cool as possible. These birds may be more susceptible to problems from the bacteria that grow in warm water.
Commons are cavity nesters, and will need a raised wood duck style box for nesting. The box will need to be some what larger than average wood duck nesting box, to accommodate the much large Common hen. Clutches consist of 8-10 eggs and are incubated for 30-32 days.