Clue to kittiwakes' winter journeys discovered

Kittiwakes, which have seen declines in numbers in much of northern Europe and the UK in recent years, tend to leave their summer breeding grounds earlier if they fail to breed and then head 1,800 miles to over-winter off Canada.

But birds which successfully reared their chicks to fledging tended to stay close to Britain the following winter, the researchers from the Centre for Ecology and Hydrology (CEH) and the British Antarctic Survey found.

The scientists suggested the successful breeding birds used more energy and resources to rear their chicks and had to stay until the end of the breeding season, making them unable to undertake the long journey west.

But they also said the pattern could be repeated over the years, so that birds repeatedly over-wintered in the western Atlantic and failed to breed in the summer, possibly because of genetics or environmental conditions in the wintering areas.

The CEH's Dr Maria Bogdanova, who led the study published in the Proceedings of the Royal Society B journal, said understanding where the birds go could have important implications for international conservation efforts.

There was a need to look at the conditions in the areas the birds spent the winter, to examine if there were conservation actions which could help them.

And identifying differences between where successful and unsuccessful birds go is important for defining key over-wintering grounds for kittiwakes, which are experiencing poor breeding seasons more regularly.

The researchers said it was possible the recent declines in numbers of kittiwakes could be caused by an interaction of poor breeding seasons and harsher winter conditions.