I was told off in no uncertain terms by an African headmistress complaining about people who put out food for the birds - then they moved and the next people didn't put out food!  The birds starved as they had never had to fend for themselves!!  I have never fed the birds since, but I do keep the bird bath filled up for them!  And this winter it has frozen over a number of days, but melts quickly once the sun is up!