One of our daily morning jobs is checking on and refilling the bird feeders in the front and back garden. The children love this job and then we all sit in the kitchen window and watch the birds come down for the food. We often have Squirrels that come for the monkey nuts. They have to be quick though because the jackdaws watch us from the roof across the road and as soon as we have gone in they swoop down and grab the nuts for themselves!
I have a great book that has a page for each bird. It includes most of the common UK garden birds and there is a little picture to press that plays the bird call for you. The children love it and often grab it from the bookshelf after filling the bird feeders, so that they can identify the birds that come and feed.
Sometimes we make bird feeders too. Especially as the weather starts to get colder and the birds need more help.