Most pairs raise two broods per year, and the male may feed newly fledged young while the females incubate the next clutch of eggs.

The next morning they were on their way north - to nest, to breed, to fledge young.

The fledging period is thirteen or fourteen days, with around 44% of nests where the outcome was known successfully fledging young.

A Danish study showed that predation by mammals, especially red foxes, was an important cause of mortality in newly fledged young, with 36% dying between fledging and independence.

Colony size did not influence the laying date, the clutch size or the number of successfully fledged young, but this species does not form large colonies anyway.

Most failures to fledge young are due to predation.

Both parents feed the chicks and fledged young.

Red foxes are an important cause of mortality in newly fledged young.

Fifty to seventy percent of the nests successfully fledge young.

Birds seek them out all year but especially in June and July, when the moth caterpillars are largest, and they are accompanied by their just fledged young.