We studied nocturnal and diurnal behavior of breeding American Avocets (Recurvirostra americana) at the Jay Dow, Sr. Wetlands in the northwestern Great Basin, USA. Seven-day observation periods were centered on two full moons when ambient light was maximal and auxiliary lighting unnecessary. We recorded avocet density, habitat use, interbird distances, and behavior three times daily (beginning at 07:00, 15:00, 23:00 PST) for 14 days. We calculated the mean proportion of individuals within flocks engaged in four behavior classes (foraging, copulating, agonistic, other). Foraging birds were further subdivided by technique (pecking, dunking, scything). Avocets copulated with similar frequencies during the morning, afternoon, and night. Avocets were more aggressive and closely spaced at night than during day. The full repertoire of behaviors seen during daylight also occurred at night, though frequencies of particular behaviors, flock location, and interbird distances varied among morning, afternoon, and nighttime observations. The role of nocturnal reproductive behavior should be assessed in species generally perceived as being diurnal.