I was in Oxford again today. As I was striding along Hythe Bridge Street, I glanced over the bridge to have a look at the canal. In the foliage on the bank next to Upper Fisher Row was a pale female mallard (Anas platyrhynchos) with at least two tiny chicks. I stopped and watched them as they moved in and out of the broad-leaved water plants (irises?). Lots of people hurried by me as I was stood there, but none stopped to look.
I am not sure that this is the earliest I have seen chicks, but February the 4th does seem unusually early. If I remember correctly, a mallard on the Reading University Lakes had 16 chicks in February a few years ago, but they subsequently all died when a cold spell came along in March. However, the short-term future of the Oxford chicks looks good: the -5 degrees C forecast for Sunday night has now been revised upwards to 0 degrees C.