Roseate tern

Voice

Two sounds do the work. The contact call is a soft, two-syllable chu-vik with the stress at the end, close to the call of a Spotted Redshank, and it cuts straight through the racket of a mixed colony. The other is a rasping, grating aaach, shorter and harder than the scrape of a Sandwich Tern. Both carry over water at ranges where bill colour is long gone, and on a bird passing a headland the voice is often the only hard character on offer.

Identification

Common Tern sized but whiter, paler and far longer tailed. The upperwing is evenly pale grey with no dark wedge in the outer primaries; all that breaks it is a thin dark line along the leading edge of the hand. The bill is close to all black early on and takes a red base from around June, on some birds running half way to the tip. The legs are orange-red and clearly longer than an Arctic Tern's. Fresh birds carry a rose flush across the breast, visible only at close range in soft light and worn off within weeks. On a settled bird the white streamers project five to eight centimetres beyond the closed wingtip. Juveniles are coarsely scaled dark brown above with a dark forehead and black bill and legs. The length given here includes those streamers, as most field guides do; sources that measure the body alone come out some five centimetres shorter.

Confusion species

Upperwing, tail and voice carry the identification. From above Roseate is evenly pale grey: it lacks the dark wedge that spreads through a Common Tern's outer primaries as summer goes on, and it lacks the crisp narrow trailing edge of Arctic Tern, leaving only a thin dark line along the leading edge of the hand. The streamers are white and long enough to project well beyond the wingtip on a perched bird, further than on Arctic and much further than on Common, where they reach the wingtip at best. The bill is mainly black with a red base late in the season, against Common's orange-red bill with a black tip and Arctic's uniform blood-red bill. The rose flush on the breast is a bonus rather than a feature to build on: it fades fast and hard light kills it. In flight the bird looks shorter winged and longer bodied behind, with a faster, stiffer, shallower beat, as though flying at half amplitude, where Common and Arctic are looser and springier. When doubt remains, the call settles it. Sandwich Tern is larger and paler still but has a yellow bill tip, a shaggy crest and a quite different two-syllable screech.

Habitat

Nests on small rocky islands and shingle banks close inshore, favouring places where dense herb growth, loose stones or nest boxes give the chicks cover, so the nest itself is rarely in the open. Feeds over shallow water with a run of tide, over sandbanks and in tidal races, diving from greater height and at a steeper angle than Common Tern and staying under longer. The diet is almost entirely sandeel and young clupeids. After the breeding season birds gather on sandy beaches, groynes and piers, generally in mixed tern roosts.

Range and movements

Rockabill, off Co. Dublin, holds by far the largest colony in Europe; Lady's Island Lake in Co. Wexford is the second, Coquet Island off Northumberland is the only regular British site, and smaller numbers nest on islets off Brittany and on the Azores. Colour-ringed birds move freely between these places, so a bird at one colony is often a known individual from another. Elsewhere the species breeds in the Caribbean, along the eastern seaboard of North America and across the tropical Indian and Pacific Oceans. The European population winters on the coast of West Africa, concentrated in the Gulf of Guinea.

• Breeding (summer)
• Passage
• dark = core range, pale = thinly spread

Where and when to look

Boat trips from Amble around Coquet Island in June and July give the easiest close views in Britain; landing is not allowed, but the birds come to the boat and the terraces are in plain sight from the water. In Ireland the colonies themselves are closed, so work the post-breeding roosts instead: from late July into September Rockabill birds gather in tern roosts around Dublin Bay and along the Irish Sea coast, where a telescope on a settled flock will give you streamers, black bills and, with patience, readable colour rings. Get the sun behind you and let the flock call.

Conservation status

Least Concern globally, but the European total runs to only a couple of thousand pairs on a handful of sites, which makes colony management the whole story. Rockabill went from under two hundred pairs to well over a thousand once it was wardened, rank vegetation was cut back and nest boxes were put out; Coquet Island did the same with terraces and boxes while large gulls were kept off the nesting slopes. Rats, mink and gulls, summer storms that flood low-lying nests, and trapping on the West African wintering grounds remain the pressures, and the concentration is itself the risk: one bad season on one island shows up in the European figure.