common tern

common tern (Sterna hirundo) [state endangered]
Photo © Alan Murphy Photography

FEATURES
The common tern averages 13 to 16 inches in length (tail tip to bill tip in preserved specimen). It is gray on its back and wings, and white on the ventral (lower) side. The top of the head is black. In summer, the bill is red-orange with a black tip, and the feet are red-orange. The immature birds and winter adult have a partial black cap, and the bill is black or dark. The forked tail is an obvious trait of this species.

BEHAVIORS
The common tern is a common migrant statewide and a rare summer resident on Lake Michigan. Its call is “kee-ar” or a series of “kip” notes, which may be heard as the bird is flying. Spring migrants begin arriving in Illinois in April. These birds nest in colonies on sand or gravel, and in Illinois they have nested on small islands off the shore of Lake Michigan. Often a depression in sand or rocks is used for the nest to which dried grasses or other items may be added. Two or three, brown eggs with dark marks are laid by the female, with one egg produced per day. Both male and female share incubation duties over the 24- to 26-day incubation period. Fall migration begins in August. The common tern winters from the southern United States to South America. This bird dives from flight to catch the fishes that make up its diet.

​Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Laridae

The common tern is endangered in Illinois. The population of the common tern has always been low in Illinois, but disturbance of its nesting colonies by predators, humans, Canada geese and gulls have caused further declines. Protection of nesting colonies should help to insure its successful nesting. Preservation and proper management of the entire shoreline area of Lake Michigan would enhance the survival chances of this species in the state.