Garden warbler

Despite its name, the garden warbler (Sylvia borin) is less likely to be seen in gardens than in woodland and scrubby areas such as alongside rivers where the undergrowth is dense.

The garden warbler is a summer migrant to the British Isles, spending its winters in Africa and arriving at any time from late April to mid-May. It can leave again as early as mid-July or at any time during August or early September. It is found throughout Britain apart from northern and eastern Scotland. In Europe, its range extends as far as western Siberia.

Appearance and behaviour

The garden warbler is a plump bird, some 14 centimetres (5.5 inches) in length. It has a stubby bill, a round head and quite a short tail. The plumage is brown above and lighter below, with hardly any distinguishing features apart from a lighter coloured marking through the line of the eye and a greyish tinge on the neck. It could easily be mistaken for a blackcap were it not for the latter’s black cap! Male and female garden warblers look alike.

Like the blackcap, the garden warbler takes jerky, undulating flights from tree to tree, but tends to spend more time skulking in the undergrowth.

The garden warbler has a pleasant, rapid, flutey song that is full of varied notes. It also has a “tac-tac” call and a grating “churr”.

Breeding

The garden warbler’s nest is quite large for a small bird, and is constructed in thick undergrowth close to the ground, such as in a blackberry bush. Long dry plant stems are collected and woven into a nest, which is then lined with soft material such as spiders’ webs. 

Four to five eggs are incubated by both partners for up to 14 days, and both share in feeding the chicks, on insects, larvae and spiders. Berries will be added to the diet as they ripen. Unfortunately for the garden warbler, it is often tricked into raising cuckoo chicks, their nests being regular targets for cuckoos. The garden warbler seems unable to tell the difference between its own young and that of the cuckoo, and will be just as conscientious in its parenting behaviour towards the “foster chick”.

Young garden warblers leave the nest at around 10 to 14 days after hatching, although they have not yet fledged. A second brood may be raised, although time is short before the birds must make the long flight to Africa for the winter.

© John Welford