I'm amazed that they find any invertebrates when it's this cold, but they must be finding something or wouldn't be there.

Can't put fat balls or anything similar on my balcony, had to stop that and get the carpet cleaned once before.  I would love to put some food on the grass below but have one wretched neighbour who complains to the council if anyone dares to feed the birds.  Others have tried and we have all got a stern letter warning of "Enforcement Action" if we encourage vermin.