Common Tern

 

Common Name: Common Tern

Class:  Aves

Order: Charadriiformes

Family: Laridae

Genus: Sterna

Species: Sterna hirundo

 

 

 

Taxonomy/Description

 

Common Terns are shorebirds in the family Laridae which groups them together with Gulls. They are smaller, common terns. They are a smaller tern as they are 14.5 inches (37cm) in size with a 30 inch (76cm) wingspan. Common Terns are monochromatic which means that both males and females look alike. They are fairly graceful and slim birds with greatly forked tails. During the breeding season, adults have red legs and an orange bill with a black tip. They have a white face and a black cap with a medium-gray neck, breast and belly. Their back and upperwings are back and they have a dark wedge on their outer primary feathers. By late summer, the outer 5 primary feathers are dark because the primary pattern darkens with wear. Their rump and tail are white and their outer retrices have dark edges. During the nonbreeding season, their bill is mostly black and their black cap starts from the eye to the crown and then extends from the eye to the nape of the neck. Juvenile Common Terns have pale legs and a pale bill that will become darker as they age. Their forehead, foreneck, breast and belly are white. Their wings are gray with brown tips and their tail is short with black tips.

 

Habitat/Diet

 

The breeding range of the Common Tern extends through most of eastern and central Canada, the eastern seaboard and parts of the Great Lakes Region. They are found in southern Peru and northern Argentina during the winter. Populations of Common Terns are declining around the Great Lakes Region because they are losing nest sites due to the growing Ring-billed Gulls populations and rising water levels. Common Terns can be found surrounding lakes, oceans, bays, ponds and small islands.

 

Fish compromise 90% of the Common Tern's diet, with the rest being crustaceans and insects. They forage by dropping from the air and diving into the water after their prey.

 

Behavior/Reproduction  

 

Common Terns nest colonially in tens to thousands. During courtship displays, the male will strut and waddle with his next fully extended, his bill pointed up, with his tail cocked and breast expanded around the female. He will also feed the female as part of a ritual, and will be interrupted many times by a different male trying to lure the female away. Common Terns are monogamous and have one brood per year. Occasionally they will have 2 clutches, but the second is rarely successful. The mating pair will have a separate nesting and feeding territory. The male will usually defend the feeding territory. Both males and females will build the nest which is usually located in sand shells or pebbles. It is shaped by the body and lightly lined with grass and seaweed. Occasionally the pair will not build a nest. The female will lay 3 eggs that can range in color from olive to buff to brown marked with brown. The third eggs is usually the smallest and least likely to survive. Both parents will share the responsibility of incubating the eggs for the 21-27 day period. The development of the young is semiprecocial which means they are mobile, fed and remain at the nest. Both sexes will care for the young which are able to fly 26-27 days after hatching.

 

Where to see them in WNY

 

Common Terns can be seen around the Niagara River and Lake Erie, though their numbers are decreasing due to lack of nests because of expansion of Ring-billed Gulls.

 

CAC is a program of the Institute for the Study of Human-Animal Relations at Canisius College in Buffalo, NY.