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Common Tern

Status Common in summer. Breeds. As a rule, Common Terns arrive in early May (average 3 May, earliest 27 April). They are common to abundant in summer in the vicinity of breeding colonies, particularly those along the Southwestern and Eastern shores. Because Common Terns fly at relatively low levels to dive for small fishes near the surface, they avoid water muddied by tidal action like that along the Minas Basin. The main fall migration takes place between late August and the end of September, and stragglers are seen in October. The latest fall record is of a bird seen near Pictou on 11 November 1963 (E. Holdway). Later sightings could involve confusion with Forster's Tern.

Description Length: 33-40 cm. Adults in summer: Mantle of pearly gray across back and wings; whole top of head black; sides of head, throat and tail white; breast and belly very pale gray; tail forked; outer web of outer tail feathers gray; bill red at base, black at tip; feet red. Adults in winter: Similar but only hind part of crown is black; forehead white. Juveniles: Similar to winter adults but back somewhat mottled and buffy, tails much shorter, and distinctive dark mark on the inner forewing.

Breeding Nest: A mere depression scraped out in the turf or sand, sometimes with a lining. In my experience, nests always occur in colonies numbering from a few to many hundred pairs, usually on coastal islands but sometimes on mainland beaches remote from human intrusion or on islets in freshwater lakes. On 5 August 1966 Marie Henry found one newly hatched young being fed by a parent on a small, bare island in Kejimkujik Lake. The species breeds extensively on lakes elsewhere in its range. Eggs: 3; olive-green to olive-brown, heavily marked with dark brown blotches, usually heaviest around the larger end. On 12 June 1937 about 100 pairs of terns were nesting on Indian Island, Lunenburg County. Perhaps 60 pairs were Common Terns and the rest were Arctic and Roseate Terns; none of the many eggs had yet hatched.

Range Breeds from Great Slave Lake east to southern Labrador and Newfoundland, south to the northern tier of the United States, and southward along the Atlantic coast locally to the Caribbean. Winters from South Carolina southward and on the Pacific coast. Widely distributed in the Old World, from the British Isles to eastern Siberia.

Remarks Our three breeding terns the Common, Arctic, and Roseate are known to those who live along the shore as "mackerel gulls." In life it is difficult to distinguish between them. Generally, in summer the bill of the Common Tern is reddish with a black tip, that of the Arctic is blood-red and the Roseate's may be all black or have a small reddish area about the base. The Roseate has a longer tail than the other two, and the experienced field observer will detect its whiter, more slender and elongated appearance. The legs of the Arctic Tern are slightly shorter than those of the other two, and its squatty appearance on the ground may be helpful. In flight, the broad, sooty trailing edge on the underside of the Common Tern's primaries contrasts with the narrower, sharper edges of the Arctic and the whiter underwings of the Roseate. The grating quality of the Roseate Tern's call is also distinctive. At rest, juvenile Common Terns can be distinguished from the other two by their darker "shoulder" mark which appears as a dark bar on the upper forewing in flight.

A visit to a colony of nesting terns, particularly a large one, is an experience long remembered. As the nesting ground is approached, the angry birds come to meet the intruder scolding vociferously. When the nests are reached, the harsh, screaming tearr, tearr, tearr reaches its highest pitch, and is accompanied by savage dive-bombing, as with folded wings the birds drop at terrific speeds to within centimetres of the intruder, sometimes spraying him with highly odoriferous, regurgitated fish.