The latest detailed report into the decline or increase in British bird species published yesterday (Nov 22) shows that some have done much better than others – but that early nesting periods brought about by climate change is causing worry about insect-eating species.

The problem is that chicks can hatch before the gluts of insects appear which are normally the main source of food. This leaves parent birds in a desperate search to find enough insects to feed their young.

The survey is conducted annually by the British Trust for Ornithology and the Government backed Joint Nature Conservation Committee, which believe that bird numbers are a yardstick to the general health of the environment.

The survey includes the bad news that 20% of 117 British bird species monitored over the past 40 years have lost half their numbers. And of those, 39% are breeding earlier and are therefore at further risk because of lack of food for their offspring. The nightingale is at risk of joining this group.

But the news is not all bad. Other species have doubled their numbers, probably benefitting from milder winters, including buzzards, green and spotted woodpeckers and nuthatches.

For the full list of gains and losses, go to www.bto.org/birdtrends2010/