Dunnock

Breeding: This species makes up for its drab appearance with its randy breeding behavior. Females are often polyandrous, breeding with two males at once, and thus giving rise to sperm competition. Males compete for mating access to the female, but DNA fingerprinting has shown that chicks within broods often have different fathers, depending on their success at monopolizing access to the fertile female. Males try to ensure their paternity during courtship by pecking at the cloaca of the female to stimulate her to eject the sperm of other males with whom the female has recently mated. Males provide parental care in proportion to their mating success, so it is not uncommon to see two males and female provisioning nestlings at one nest. Polyandry is rare in birds, with only about 2% of species showing such a mating system; the majority are monogamous, where one male and one female breed together.