The Black Tern (Chlidonias niger) is a small, dainty member of the "marsh terns," a group tied to freshwater and known for a light, fluttering flight quite unlike the powerful wingbeats of typical sea terns; unlike its relatives, it never plunge-dives, instead picking prey from the water surface in flight or snapping insects from the air. In summer plumage the head, neck and entire underside are sooty black, contrasting with a blue-grey back, wings and shallowly forked tail and a white undertail that stands out against the dark belly; in winter and in juveniles the underside turns white and the black cap shows a characteristic dark patch extending down the breast sides, a useful field mark. At 22–26 cm long, with a wingspan of roughly 56–62 cm and a weight of 50–75 grams, it is notably smaller and quieter than the region's sea terns, its call a thin, squeaky "kjäh" or "kik" heard mainly around the colony.
In Sweden the Black Tern breeds almost exclusively in the southernmost provinces — Skåne, Blekinge, Öland and a handful of plain lakes in Östergötland and Närke, including Tåkern and Kvismaren — with a small population of just 150–350 pairs that fluctuates considerably from year to year depending on water levels and vegetation. Classed as Vulnerable (VU) on the red list, mainly due to wetland drainage and overgrowth, it is a long-distance migrant that winters in West Africa. It nests in loose colonies on nutrient-rich lakes, building a floating platform of reed and plant material on lily pads or floating mats; a female lays 2–3 eggs, incubated by both parents for about three weeks, and breeding success depends heavily on stable water levels, since heavy rain or falling water can drown or expose the nests. Its diet consists of water insects, dragonflies, mayflies, small fish and frog tadpoles, taken in its characteristic buoyant, hovering flight over reed and lily-pad beds.
Read about this species in Swedish →