Is it normal to see baby birds in January?

QWhile walking in Newcastle city centre in mid-january I came across a Mistle Thrush in a tree. Upon a closer look I found it to have a nest with chicks! Is this unusual, as to my knowledge they should not be nesting until March-april. They seem to be doing fine, and the adults are getting plenty of food for them. Matthew Carroll, Newcastle

AIt is unusual to see this, but not unheard-of, and the reason why it happens probably has something to do with the micro-climates that we get within our cities – winter temperatures can be several degrees above those in the surrounding countryside, because of the heat created by human structures and activities. Woodpigeons can nest at pretty much any time of year, and semi-tame Mallards have been known to nest in winter, while Stock Doves and Moorhens both have breeding seasons that can start very early and end very late. Where songbirds are concerned, though, we’ve heard of, and seen, previous examples involving Blackbirds and Song Thrushes, including one of the latter using the sun-visor of an amber traffic light as a platform for its nest, thus cleverly gaining constant heat from the red light! Mistle Thrushes aren’t especially early nesters, but the males do sing from early winter or even late autumn, including in the worst winter weather (hence their old name of ‘stormcock’), so they do potentially get a head start on pairing off. One final possibility is that these are young, first-time breeders, and that they’re effectively testing the limits of when they can and can’t breed.