Dunnock

Fascinating facts about the Dunnock

• At just 13–14.5 cm long, the dunnock is about the size of a robin yet it can fit more than 100 copulations into a single day, each lasting only one-tenth of a second – a breeding frenzy that turns every encounter into a race for sperm.
• DNA fingerprinting of dunnock broods reveals that chicks in the same nest often have different fathers, showing that polyandry is common and that females regularly mate with multiple males to spark intense sperm competition.
• When food is abundant, female dunnocks reduce their territory size dramatically, allowing males to more easily monopolise several females; this shift favors male reproductive success over female advantage.
• A typical dunnock nest, built low in a bush from twigs, moss, wool or feathers, holds three to five unspotted blue eggs, and the same nest can be tended by up to three adults – two males and a female – all feeding the chicks together.
• Despite a strict dominance hierarchy among males, the alpha male does not gain more paternity than his lower-ranking rivals; instead, paternity is usually shared equally across the group, highlighting how social rank does not always translate into reproductive power.

At a glance

About the Dunnock

The dunnock (Prunella modularis) is a robin-sized passerine, measuring 13–14.5 cm, with a drab brown back streaked with blackish tones that blend seamlessly into hedgerows and garden scrub. Its dull grey head, fine pointed bill, and subtle brown underside give it a camouflage that belies a surprisingly active personality. When a male feels challenged, he flicks his wings in a rapid “shufflewing” display, a behaviour that has earned the bird its old nickname. Its voice cuts through the foliage with a shrill, persistent tseep and a delicate trilling warble, a sweet, thin song that hints at the bird’s hidden complexity. Across temperate Europe, southwest Asia, and the introduced range of New Zealand, dunnocks favour lowland woodlands, shrublands, gardens, and hedgerows, foraging on the ground for insects, spiders and other detritivores. Their social structure is fluid: males may share territories in strict dominance hierarchies, while females typically hold exclusive ranges. This flexibility fuels a suite of mating systems, from monogamy to the rare polyandry that sees a single female mate with multiple males, prompting intense sperm competition and a startling one-tenth-of-a-second copulation that can occur over a hundred times a day. The result is a dynamic breeding tableau where up to three adults may provision a single brood, illustrating the dunnock’s remarkable adaptability in both habitat and reproductive strategy.

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