A few weeks ago when I was out cycling with some friends, we saw a few birds who looked like they were sleeping. Someone asked me what they were doing, and I said they were resting or sleeping but I'd ...

Humans do very little when we sleep. This might not seem like a big deal, until you look to the dolphins as they sleep and swim with the pod. Or fur seals, who can sleep while watching out for sharks.

Have you ever seen a bird sleeping on a thin tree branch and wondered why it does not fall? While humans may lose their grip when their muscles relax during sleep, many birds can remain safely perched ...