Birds, winter, spring and whaterver

It's mid April, there's still snow on the ground. Usually by now the grass starts to show, the birds that flew away for the cold season are getting back and have started to look for a partner. Some birds have already come back but it's still cold so there isn't a lot for them to eat, the branches still look pretty dead to me but when you see the birds making a return you just have to know they can't be wrong, if they're here it's because winter's leaving. Right?