Gray-backed Tern

Onychoprion lunatus




Gulls, Terns, Skimmers (Laridae)

Code 4


Code 6



Egg Color:

White with dark brown speckling.

Number of Eggs:


Incubation Days:


Egg Incubator:

Both sexes

Nest Location:

On ground.

Nest Material:






Gray-backed Tern: Medium sized seabird with long, pointed wings and long, forked tail. Black cap, nape, crescent shaped narrow white patch along forehead and white eye brown stripe that extends above and past the eye, black eye line to base of bill; white front, superciliary, underparts and outer tail feathers; rest of upperparts gray; black dagger like bill. Legs and feet are black. Winter adult has a faintly streaked white forecrown. Juvenile has dark gray mottled crown and nape, buff scalloping on gray upperparts and white underparts.

Breeding and Nesting

Gray-backed Tern: These terns have a long breeding period, from February to September. They nest as individuals or in loose colonies and begin nesting in February. One spotted egg is laid in a shallow depression in sand or gravel or on short vegetation. The egg is incubated for 32 days by both parents.

Foraging and Feeding

Gray-backed Tern: These terns hover over the surface of the ocean and feed by both dipping and shallow plunging, hurtling head first into the water. Their diet includes cowfish, goat fish, crustaceans and aquatic insects. They select prey that are low in water content and high in calories. They drink by skimming their bill over the surface of the water while in flight.


Gray-backed Tern: High pitched screeches, including "Bee-Doo-Bee-Doo", "bee-doo-doo," "doo-bee-doo," "buh-bee-doo-bee-doo", and bee-doo-bee-doo-bee-doo"; also emits a jerky "too toot to toot."

Similar Species

Gray-backed Tern: Differs from Sooty, Bridled, and Aleutian Terns by combination of white underparts and light gray on upperparts.


Belly, undertail coverts, chest, flanks, and foreneck.

Back, rump, hindneck, wings, and crown.
The area on top of the head of the bird.
The crown is the top part of the birds head.
Eye lineX
The line of feathers just in front of and behind the eyes. It extends back from the posterior angle of the eye. This can be a useful trait used in identification in the field since it is very noticeable.
Also called the hindneck or collar, it is the back of the neck where the head joins the body.
Parts of a Standing bird X
Head Feathers and Markings X
Parts of a Flying bird X