Polarized filters are nice, but unless they are the real high end ones you will lose up to 1 1/2 stops. May not sound like much but when dealing with wildlife photography you are typically shooting in twilight conditions and since a typical 70-300mm lens only opens up to f/5.6 at 300mm (and usually the results at 300mm f/5.6 are less then desired) 1 stop is a lot to trade for the results of a polarized filter. You would be better off putting the money used to buy a polarized filter towards a good cable release or tri-pod. Don't forget to buy some decent post production software, Adobe Lightroom or similar.