Me: Look boys, the seagulls are cleaning their feathers with their beaks.
Elijah: Oh yes, they're preening. They squeeze oil from a gland just above their tails.
Me: Oh, right, I knew that.
Credit goes to this book...
...the Usborne Complete Book of Nature. I found it at Half Price Books for less than $5, and it has been worth every penny. It is full of interesting information and excellent illustrations. Elijah and Noah both enjoy it quite a bit. It seems to be out of stock at Amazon, but if you have young children and happen across a copy somewhere, I would recommend purchasing it. :)