Stragglers migrate south in mid-fall, but the largest numbers move just ahead of freezeup. Most flocks in feeding areas are small - 5 or 6 birds, with more hens and immatures than adult drakes. Very small size, bold black and white color pattern and low, swift flight are field marks. Unlike most divers, they can fly straight up from a watery takeoff.
Largest concentrations are on both seacoasts and along the Gulf of Mexico. Inland, they will remain as far north as open water permits. Usually silent. Drakes squeak and have a guttural note; hens quack weakly.