Black tern

Voice

Fairly silent away from the colony. The call is a short, sharp and slightly nasal kik or kyeck, often in quick series during chases. A disturbed colony gives a persistent, plaintive kree-eh. Heard mainly from May to early July over breeding sites, and occasionally from night migrants in August.

Identification

In breeding plumage the head and underparts are sooty black, the wings, back and tail slate-grey, and the white undertail coverts flash behind the dark body. Bill black, legs dark red. In winter it is white below with a black half-hood extending behind the eye and, crucially, a dark patch on the breast side in front of the wing bend. Juveniles have a brown-grey, weakly contrasting saddle.

Confusion species

Autumn White-winged Tern is the classic pitfall: it lacks the dark breast-side patch, shows a white rather than grey rump and a smaller, isolated ear patch. Whiskered Tern is larger, thicker-billed and cleaner white on the body. At distance a feeding Little Gull can give the same fluttering impression, but shows rounded wingtips and a paler overall look.

Habitat

Nutrient-rich peat marshes, turf ponds, old river arms and shallow lakes with floating vegetation, above all water soldier. Outside the breeding season on large fresh and brackish waters and along the coast. Feeds on the wing, seizing insects, small fish and tadpoles from the surface or in mid-air, never diving under.

Range and movements

Breeds from Iberia and France far into Russia. The peat districts of north-west Overijssel, Friesland and the Rhine floodplain give the Netherlands an important western European population, largely on artificial nesting rafts. In Spain it breeds sparingly in northern marshes but passes through in numbers along the Ebro delta and the Andalusian lagoons.

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

Where and when to look

Visit a water-soldier lake in May or June in the early morning and watch the nesting rafts. For numbers, go instead in August to the IJsselmeer or Markermeer shore, where large flocks feed over the water in late afternoon and gather on groynes and buoys, allowing close study of moulting adults.

Conservation status

It declined steeply in western Europe during the twentieth century through drainage, eutrophication and the loss of water soldier; in the Netherlands numbers are stabilising thanks to nesting rafts and improved water quality. Colony disturbance, wave action and a shortage of insects in the breeding season remain problems, as does drought in the African wintering grounds.