Black Tern/Chlidonias niger - Photographer: Иван Петров
Black Tern/Chlidonias niger - Photographer: Иво Дамянов
Black Tern/Chlidonias niger - Photographer: Борис Белчев
Black Tern/Chlidonias niger - Photographer: Иво Дамянов

L 22-26 cm, WS 56-62 cm. Commonest marsh tern, breeding in freshwater marshes with patches of low, floating vegetation, often among Black-headed Gulls for protection. Summer visitor (mainly late Apr-Sep), winters in Africa. In Britain & Ireland, occasional large migrant gatherings or coastal passage, but seldom numerous.
IDENTIFICATION: Adult summer: All-black head and body, rather uniform dark grey upperparts, white undertail, and dark legs and bill; head and underparts mottled or patched with white on moulting adults in spring (before May) and summer/autumn (white feathers on head already appearing in Jun). - Adult winter (head and body plumage fully acquired Sep onwards): Much as juvenile, but upperparts plain grey, lacking scaliness, and outer 5-7 primaries darker than rest. - Juvenile: Extensive black cap and obvious dark breast-side patches; scaly pattern on darkish saddle and wing-coverts; darker carpal and secondary bars; and outer primaries not contrastingly darker than inner. Could be mistaken for juvenile Common/Arctic Tern, but note smaller size, shorter, less forked tail, slightly shorter wings, and dark breast-side patches; mode of flight (cf. above under ‘Marsh Terns’) also good clue. - 1stsummer (usually stays in winter range): Variable; like adult winter but usually differing in having darker, more worn outer primaries and darker secondaries, and on some a few scattered dark feathers on underbody and head (these safely told only in May-Jun from moulting ad.).
VOICE: Flight-call a harsh, almost multisyllabic ‘k’shlet’ (slightly recalling Little Tern), and short, nasal ‘klit’ and ‘klee-a’. Alarm-call energetic ‘ki-kiki…’, or a shrill ‘kyeh’.

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