Least Tern

The least tern arrives at its breeding grounds in late April. The breeding colonies are not dense and may appear along either marine or estuarine shores, or on sandbar islands in large rivers, or in areas free from humans or predators. Courtship typically takes place removed from the nesting colony site, usually on an exposed tidal flat or beach. Only after courtship has confirmed mate selection does nesting begin by mid-May and is usually complete by mid-June. Courtship takes the form of either an aerial display in which the female follows the flight of the male or through courtship feeding. Nests are situated on barren to sparsely vegetated places near water, normally on sandy or gravelly substrates. In the southeastern United States, many breeding sites are on white gravel rooftops. In the San Francisco Bay region, breeding typically takes place on abandoned salt flats. Where the surface is hard, this species may use an artificial indentation (such as a deep dried footprint) to form the nest basin. The nest density may be as low as several per acre, but in San Diego County, densities of 200 nests per acre have been observed. Most commonly the clutch size is two or three, but it is not rare to consist of either one or four eggs. Adults are known to wet themselves and shake off the water over the eggs when arriving at the nest. …