Where Have The Birds Gone?

I was away at the weekend when we had a cold snap with snow. When I came home the seed feeder was still one third full. Since then there seem to be far fewer birds on the feeder whenever I look. Were there a lot of fatalities or did the bad weather start other people feeding so the birds have just moved to feeding stations nearer their roosts? I can't tell but I must spend more time watching over the Christmas period.