Ultimate bird profiles: Blackbirds

Fluent, musical notes are the hallmark of this common thrush, its rich, languid song varying between individuals. In addition, the blackbird produces many different alarm calls, each relating to a specific threat.

The main singing role in the dawn chorus all over the country has been taken by the blackbird, and its mellow fluting is one of the most beautiful bird-songs heard in Britain—rated by some people even higher than that of the nightingale. The blackbird also produces a sweet, muted sub-song, hummed through a closed bill and sounding like a distant echo.

At dawn and dusk groups give voice to a persistent chorus of "pink-pink" calls. Other sounds made by the blackbird are harsher. Its nervous, scolding "mik mik mik" chatter gives notice of a prowling cat or a fox. Its tail-flicking "chook-chook" shows mild anxiety, and in winter is a sure sign that a guarded communal roost is in the vicinity.

When the need arises, the calls can develop into a somewhat hysterical, screaming rattle of full alarm. In summer, a thin "seep", which is difficult to locate, alerts the blackbird’s mate or chicks to the presence of danger, and a similar call is made to warn that a sparrowhawk or other avian predator is too close for comfort.

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A dynamic expansion into man-made habitats during the past 100 years has made the blackbird the most common resident breeding bird in Britain. Its rivals for that title include the wren and the dunnock, and in much of the north and west, the chaffinch. The blackbird used to be confined to woodland, but it has moved out into gardens, fields, parks, squares, commons, heaths, and, in hill districts, to cloughs and combes.

One reason it has been able to do this is its willingness to vary its diet. Also, it is aggressively territorial, so as the population increased with successful breeding, a tendency to spread further afield followed. Numbers are enhanced in autumn and winter by migrants from Europe. Many of the blackbirds seen in Britain at this time are in fact non-residents.

The blackbird is the only one of Britain’s three common breeding thrushes (the others are the song thrush and the mistle thrush) in which the male’s plumage differs from the female’s. A few males become well known in their areas for being partly white, some looking as if they have snowflakes on their backs. Female and, particularly, young blackbirds, with their more noticeable mottled underparts, are often mistaken for song thrushes.

Male birds are jet black with golden yellow bill and eye-ring; females are dark brown, lighter below, slightly mottled, with a brown bill. They are around 25.5cm (10 inches). 

Female blackbirds build a neat cup of dry grass, dead leaves, and mud in hedges, low trees or on ledges of buildings; they lay late March–July; usually 3–5 eggs, light blue-green with brown spots; incubation about 13 days, by female only; nestlings, fed by both parents, fly after 13 or 14 days; usually two or three broods, occasionally one, four or five. Their diet consists of insects and their larvae, earthworms; fruit and seeds.

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