Breeding

Both sexes reach sexual maturity at one year of age. The male mates with the female by swimming close to her with his head lowered and tail raised, continually whistling. If there is a group of males, they will chase the female in flight until only one drake is left. The female prepares for copulation, which takes place in the water, by lowering her body; the male then bobs his head up and down and mounts the female, taking the feathers on the back of her head in his mouth. After mating, he raises his head and back and whistles.[10]

Breeding takes place between April and June, with the nest being constructed on the ground and hidden amongst vegetation in a dry location, often some distance from water. It is a shallow scrape on the ground lined with plant material and down.[9] The female lays seven to nine cream-coloured eggs at the rate of one per day;[10] the eggs are 55 x 38 millimetres (2.2 x 1.5 in) in size and weigh 45 grammes (1.6 oz), of which 7% is shell.[16] If predators destroy the first clutch, the female can produce a replacement clutch as late as the end of July.[10]

The hen alone incubates the eggs for 22 to 24 days before they hatch. The precocial downy chicks are then led by the female to the nearest body of water, where they feed on dead insects on the water surface. The chicks fledge in 46 to 47 days after hatching, but stay with the female until she has completed moulting.[10]

Around three-quarters of chicks live long enough to fledge, but not more than half of those survive long enough to reproduce.[10] The maximum recorded age is 27 years and 5 months for a Dutch bird,[16] but the average life span for wild birds will be much shorter than this, and is likely to be similar to that of other wild ducks, such as the Mallard, at about two years.[17]