Dipper nesting and breeding
Dippers are monogamous, and the pair-bond usually lasts only for the duration of the breeding season. However, pairs can remain together from year to year, possibly as a result of attachment to a territory.
All about their nests
Nest sites are traditional, and are used by successive generations of birds. One site is said to have been used continuously for 123 years. The nest may be built in any suitable site within the territory, but it is traditionally located in a natural crevice in a stream-side cave or waterfall, although the birds readily take to cracks in man-made alternatives such as bridges, walls, weirs and culverts. The same nest is usually re-lined and used for the second brood, but only rarely is a nest from a previous year re-used.
The nest is a domed structure of moss, grass stems and leaves, with a wide entrance usually pointing down towards water. There is an inner cup of stems, rootlets, leaves and hair. It is built by both sexes over a 28 day period, with the female completing the lining to the inner cup.
A clutch of 4-5 white eggs are laid at daily intervals. Clutches are normally started between March and May. Dippers breeding at good quality sites may start as early a February, but those at high altitudes and/or near acidic streams start later, lay smaller clutches and rear smaller broods than birds on better quality sites. Pairs also rarely attempt a second brood on these poor quality sites.
The eggs are incubated by the female for about 16 days, beginning with the last egg, meaning that the brood hatches synchronously. The young are brooded by the female until they are 12-13 days old, but both parents feed the young.
The young fledge at 20-24 days but are fed for a further week, becoming fully independent 11-18 days after leaving the nest. During this time the nest site may be used by the family to roost in.
A second clutch will be started about 10 days after the fledging of the first one. The age of first breeding is one year, though males sometimes take longer.