NATURE FOCUS DUNNOCK
THE name dunnock is derived from a combination of two old English words, “dun” (brown) and “ock” (small) meaning “little brown bird”.
This is a perfect description of this rather shy and widespread bird that can be seen in low vegetation and around the edge of lawns feeding on small insects, worms and berries, and on small seeds in winter. On first glance they are often dismissed as just another sparrow and are sometimes known as hedge sparrows.
They are not related to “true sparrows” like house and tree sparrows, which are members of the passeridae family. Dunnocks are accentors and belong to the prunellidae family and as such are sometimes known as hedge accentor. The dunnock is one of the UK’S most widespread species, unlike other accentors which are restricted to mountainous regions, typically at altitudes above 1,000m.
Dunnocks are similar in size to house sparrows although they are sleeker-looking with a finer bill, an indication of their preferred food compared to the stouter bill of the seeding eating house sparrow.
The plumage of the dunnock could be described as rather drab, but on closer inspection it is rather attractive; there is a mixture of grey on the head and chest and brown elsewhere, with upper parts and flank streaked with warm-brown tones. Their movements have been described as “mouse-like” as they shuffle around under the cover of hedges and shrubs with their tails nervously flicking, resulting in yet another old name, shufflewing. Its main call is a shrill, persistent tseep coupled with a high trilling note. Its song is a rapid, thin and tinkling sweet warble - similar to the song of the wren but shorter and weaker.
Whilst dunnocks look very ordinary and plain, their sex lives are anything but. They have an open approach to mating known as variable mating. The chosen mating approach is dictated by resource availability and territory size. Females are often polyandrous – females breeding with two or more males at the same time - behaviour rare in birds. Both monogamous (one male and one female) and polygynous (one male and many females) breeding also takes place.
In polyandrous breeding, males will attempt to increase their paternity potential of the offspring by pecking at the female’s cloacae (entrance to its intestinal, urinary, and genital canals) in an attempt to stimulate her to reject other males’ sperm. It has been reported that dunnocks are able to mate up to 100 times a day and take less than one second to copulate!
Dunnocks’ nests are built low in bushes or conifers and are constructed from twigs and moss with a soft lining of hair and feathers. The female typically lays three to five plain blue eggs. As complex as the mating scenarios - the raising of the brood can be by one female and one male, by a single female, by multiple females with the part-time help from a male, by multiple females with a full-time male helper, or by multiple females and multiple males!
To complicate things further, dunnock nests are parasitised by cuckoos. When laying eggs in other host species’ nests such as reed warblers and meadow pipits the cuckoos’ eggs are similar in pattern and colour to that of the host’s egg. However, eggs laid in dunnocks’ nests are very different to the host’s blue eggs but are rarely rejected by the parents. It is thought that this brood parasitism of dunnocks’ nests is relatively recent and that with time the dunnocks will respond by increased egg rejection which, in turn, will require cuckoos which favour dunnocks’ nests to adapt the colour of their eggs.