They prefer to feed in open shallow water or along the edges of emergent vegetation. Foraging birds divide their time almost equally between shallow dives and rest periods on the water surface. Dives average 12.5 seconds in length. Prey is swallowed while under water. During the shortest days of winter birds may be forced to continue foraging for hours after dark to secure enough prey to survive.
Buffleheads form monogamous pairs.
They may even keep the same mate for several successive years as pairs return to the same breeding territory and nest tree season after season. Because of the long-term nature of the pair bond, Bufflehead pairs engage in courtship displays in nearly every season of the year. The drakes can erect their head feathers to double the size of the white cheek patch and make their heads appear almost circular in profile. Territorial males may defend small lakes or ponds to exclude other Buffleheads and even waterfowl of other species. After an aggressive display toward an intruding male, the territory holder will swim vigorously about with the female following with her neck out-stretched.