Observations on black-crowned night heron breeding success in a North Dakota marsh

Storms and mammalian predation severely reduced production in a Black-crowned Night Heron (Nycticorax nycticorax) colony in two years and drought prevented nesting in two other years from 1976 to 1980. Maximum estimated production was 2.2 young per pair in 1978, the only year production was sufficient to maintain the population.