I've been in a bird hide on many occasions. As a child, we had a nature reserve just down the road from us and we went there a lot. There were several bird hides and we would sit in them, sometimes to watch the birds but sometimes to shelter from the rain!
Now we have a Wildfowl and Wetlands centre near us, which is a big favourite for a day out with my son. They have some bird hides which give an excellent view of lots of different small birds - finches, tits, sparrows.... and other wildlife like squirrels and hedgehogs. Even my four year old will sit still and quietly in there!