Blue tits vs willow tits: a lesson in subsidies

I last saw a willow tit on my farm about a year ago. I’m searching for them again this spring, listening for their ‘chair chair’ calls, but I am worried that they may be extinct here. They are dying out everywhere: down by 92 per cent nationwide in the 50 years from 1967. And the reason is not pesticides or climate change or agriculture or habitat loss. It’s blue tits.

Willow tits have never taken to visiting bird tables, but blue tits love them. So come the spring, hordes of peanut-fattened blue tits fan out across the countryside looking for nesting holes and – hey presto – they find the little hollows that willow tits have been laboriously excavating in rotten birch trees and, being more aggressive, steal them. Some pairs of willow tits have been forced to give up four successive nest holes in a season to blue tits. And many of those that do manage to breed then watch their chicks eaten by woodpeckers, whose numbers have quadrupled, also thanks to bird tables.

I learned this from Richard Broughton of the Centre for Ecology & Hydrology in Wallingford, who has published papers on the topic and argues passionately in favour of the willow tit on what I can surely (in this context) still call Twitter.