One of these birds is the common goldeneye. These birds nest from the southern edge of Canada all the way north up to the northern reaches of Canada and Alaska. They nest in cavities, such as hollow trees or nesting boxes, near wooded lakes or rivers. The females care for both the eggs, during incubation, and the chicks, who can swim and find their own food about 24 hours after they hatch.
During the winter the goldeneye migrate south to protected coastal bays and waterways or open inland lakes and rivers. Here in my area we often see large flocks of them in open areas of the Mississippi River. There they can be seen diving under the water in search of crustaceans and small fish, during the warmer months they also eat a lot of aquatic insects. Often birders around here can be found scanning flocks of common goldeneye looking for a possible Barrow's goldeneye that might be mixed in. Barrow's goldeneye sightings are pretty rare in Minnesota so they tend to get a lot of attention.