Nocturnal incubating and brooding behavior of the Black Tern (Chlidonias niger) was studied at two colonies in successive years in The Netherlands. In late evening and early morning, nests were checked regularly for female or male nest attendance until or from complete darkness. During daytime females incubated eggs 60% of the time. At night, males took over completely, while females spent the night at a communal roost more than three km away from the breeding colonies. Few females stayed with their downy young at night and more females brooded young, as chicks became older. The total parental breeding investment (day and night) was equal (51% for males), but with higher nocturnal investment by males (79%). From six days after hatching, chicks were left unattended at night. The difference between male and female nocturnal investment might be explained by the preference for self-survival instead of clutch and brood survival. Males probably have greater interest in clutch survival than females, as they are not certain to maintain the pair bond after egg loss within or between seasons. Due to increased human disturbance in Dutch wetlands, chicks now leave their nests permanently more often. This may lead to more frequent cases of chick starvation, as sometimes the young cannot find alternative resting sites.