I CANNOT help Barbara Hudson (Letters, February 10) on bendy buses, but I can on the birds. They are pied wagtails.

In winter many birds form dense roosts and over the past few years the pied wagtails from York and the surrounding area have been using the plane trees in Parliament Street. At peak times there are up to 700 birds in there.

These urban roosts have numerous advantages. They help increase the overall warmth of the flock on cold nights; the density of birds actually aids protection against predators; and, most impressively, there is evidence that birds can use the flock to learn the location of good food sources.

I’ve noticed a lot of traffic to my blog (Why Watch Wildlife?) this year based on posts about these birds, so I’m delighted so many people are obviously being as attentive as Barbara.

If readers are passing through Parliament Street as the sun rises or sets, do look up at the trees.

David Craven, York