The Dunnock (Prunella modularis) is an understated, grey-brown skulker of hedgerows and spruce thickets that reveals itself mainly by voice. Its blue-grey head and breast, the source of its Swedish name "iron sparrow", are finely streaked, the back and wings are brown-streaked with paler wing bars, and the belly is dirty white with faint flank streaking. The key identification feature is the bill: thin and pointed for an insect diet, quite unlike the thick, seed-cracking bill of the House Sparrow it superficially resembles. Despite the name, the Dunnock is not a true sparrow at all but belongs to its own family, Prunellidae. Measuring 13-14.5 cm, it usually creeps low through dense cover, though the male sings from an unusually exposed perch, treetop, rooftop or wire.
The song is a fast, silvery, high-pitched strophe lasting two to three seconds, repeated with short pauses; the contact call is a sharp "tsiih". Dunnocks breed throughout Sweden, in spruce and mixed forest undergrowth, gardens, mountain birch forest and hedgerows, with a large population of 1-2 million pairs. The nest, low in dense spruce brush or juniper, holds 4-5 distinctive turquoise-blue eggs incubated for 12-13 days. The species is best known among ornithologists for an unusually complex mating system that can include polyandry, polygyny and even polygynandry within a single population, made famous by Nick Davies's studies at Cambridge in the 1980s that showed broods often have mixed paternity. Diet shifts from insects, spiders and small snails in summer to seeds and berries in autumn and winter, when Dunnocks often visit gardens, picking up spilt food beneath feeders rather than perching on them. Most Swedish birds are short-distance migrants to Western Europe, though a growing number now overwinter in the south of the country.
Read about this species in Swedish →