Hatchlings reach the fledgling stage in three to four weeks but remain with their parents until migration. Pre-fledgling mortality rates are high, but adults may live 10 years or more. They feed almost entirely upon small fish and require shallow water areas near their nesting sites that provide abundant small fish populations. Sites for breeding and nesting are generally bare or sparsely vegetated. Nests within the colony, or ternery, are scattered, and only the area directly around the nest is defended.
Terns choose sites that are well-drained and away from the water line.
The scrape may be lined with pebbles or small shell fragments. Interior least terns migrate in small loose flocks, arriving in Missouri from late April to mid-May. They leave for their wintering areas in August and September. It is unknown where the terns go during the winter. However, unidentified terns have been found during the winter in Central and South America.