Ten million blue tit chicks died during summer

As many as 10m blue tit chicks were killed off during the wet summer, making it the garden bird's worst ever recorded breeding season.

	Britain is home to around 3.5 million pairs of blue tits

Almost half this year's young fell victim to a shortage of food, caused by the weather, according to figures released yesterday by the British Trust for Ornithology (BTO).

The blue tit was one of seven species that suffered their worst ever breeding productivity - others include the great tit and the willow warbler.

The slump was discovered by volunteers carrying out the BTO's Constant Effort Sites Scheme (CES) in which nets are set to catch and record bird numbers in the same time and place each year.

Blue tit breeding was down 48 per cent - the worst season since the CES began 25 years ago.

"This is an alarm bell for these birds. They have been hit hard," said Paul Stancliffe, BTO spokesman.

"Around the time that blue tits would be hatching we had incredibly cold, wet weather. It didn't just last a few days, it was May, June and July.

"One young blue tit needs 100 caterpillars a day and there can be up to 10 in a brood, which means 1,000 caterpillars. But the caterpillars weren't emerging or they were being washed off the leaves by the rain. Young were dying in the nest boxes because they weren't getting the food they needed."

Chicks which did manage to leave their nests suffered when their thin plumage suffered frequent soakings.

The problem was less severe in the south where a warm, sunny April allowed some blue tits to fledge successfully, but birds in the north fared badly.

Britain is home to around 3.5 million pairs of blue tits, with a lifespan of three to four years, and they have an average brood of six. But as they only breed once a year a disastrous season has severe implications.

"In the short term we will see low numbers of blue tits around and if there is a harsh winter it could compound things by killing off more of the adults. In the longer term, if we have another appalling spring next year things would start to look bad for the blue tit," said Mr Stancliffe.

"There are still a lot of blue tits out there but if you're not replacing your young each year then it could start to become endangered."

A prolonged breeding decline could see the blue tit placed on the amber list of endangered birds, while a population crash of 50 per cent would be enough to put it on the red list which involves direct action to save the species.

Other birds which suffered their worst breeding season since records began were the great tit, which saw numbers drop 33 per cent, the reed warbler, down 27 per cent, the whitethroat, down by a quarter and the willow warbler, which dropped by a fifth. The tree creeper plummeted 55 per cent and the willow tit 63 per cent, but the numbers recorded were too low to be considered reliable.

The study contained good news on long-tailed tits which enjoyed their best ever breeding season, up by 48 per cent on the long-term average thanks to early nesting before the wet weather.

Caterpillars and moths, which birds feed on after hatching, are in the grip of a long term decline which has seen their numbers drop by a third since the late 1960s as a result of more intensive land use and climate change.

According to Butterfly Conservation blue tit chicks eat 35 billion caterpillars a year, but the charity confirmed that they had suffered as a result of the poor summer.

"It has been a really bad year for moths," said Richard Fox, manager of Moths Count which is part of Butterfly Conservation.

"Moths are cold-blooded and if their surroundings are inclement or cold the adult moths can't fly which means they can't eat and can't mate. They can't do the things that produce more moths."