Black tern

The black tern (Childonias niger) has been likened to the swallow in its graceful flight over water, beating to and fro and taking insects from just above the surface.

The black tern is a migratory bird that breeds over much of Europe and winters in Africa. Within the United Kingdom it is generally only seen on Spring and Autumn passage, in England and Wales, as it breeds here only very rarely. It is most likely to be seen near freshwater lakes, including reservoirs and flooded gravel pits.


Appearance

Male and female black terns are very similar in appearance, being about 23-25 centimetres (9.5 inches) long. The black tern is therefore similar in size to the little tern, but bulkier in shape. The wings are longer and broader and the tail is only just forked. The bill is black and the legs reddish-brown. The summer plumage is very distinctive, being black on the head, chest and underparts as far back as the underside of the tail, which is white. The upperparts are black towards the front but shading to grey further back. The wings are grey both above and below.

In winter much of the black colouring is lost, leaving a black cap contrasting with white on the face and underparts, and slatey-grey plumage elsewhere.


Breeding

The black tern returns to its breeding grounds in late April or early May, the nesting sites being in dense vegetation close to water, or on islets of vegetation floating on the surface. Breeding colonies are formed with several pairs nesting close together. The nest itself comprises dry reeds and is built by both partners.

The clutch usually comprises three eggs, but sometimes only two, laid in May or June. Should the nest be destroyed, the pair may try again as late as July. Incubation, for up to 17 days, is done by both birds in turn, after which they also share the feeding of the chicks, which they do at frequent intervals.

Black terns leave for their winter quarters in August or early September.

Food for black terns consists mainly of insects, caught on the wing as described above, but they will also take larvae and small fish.

The black tern has amber conservation status in the UK due to constant threats to its habitat and its relative rarity as a visitor.

© John Welford