Suggestions for white birds?

I have been trying to perfect my technique for white birds such as great egrets. I seem to do ok with spot exposure overcompensated +.50 if I focus on the body but when I try to focus on the eye I find it hard to keep on track and pick up the background luminance which gives me an overexposure on the bird .
I wonder if I could get imput on technigques people recommend for exposure for
1. white birds in flight against the sky.
2..whie birds against greenery.
3. white birds on the water.
Thanks

Robin,
I shoot a lot of Egrets and Great White Herons here in Florida and my settings are the same as I use for all my wildlife shooting: center-weighted exposure and single center-point focus. I use these for both stationary birds and birds in flight; front-lighted or back-lighted. I've seldom gotten blown out whites with this setup and it gives me the freedom to move from white Herons to Great Blues without having to fool around changing my exposure settings. I do not use any exposure compensation. Seems to work with my Canon 7D.

Jim