I mostly shoot birds. The simplest thing to keep in mind is that if the background is brighter than the bird use + compensation. If the background is darker than the bird use - compensation.

The reason is that unless you spot meter on the subject the camera will will try to lighten the dark background and will wind up over exposing the bird. With the same logic, the camera will want to darken the very bright background thus under exposing the bird. If you look at my post from yesterday you will see examples of both. I used + or - two thirds to one stop. All pictures were taken from the same spot at the same time. The dark backgrounds were in the shadow from my house.

http://www.uglyhedgehog.com/t-519968-1.html

Of course if your bird fills the frame [mine seldom do] compensation may not be necessary at all.


---