Winter is the season for heading to Skagit County and photographing bald eagles. If you go to the right places you can see 20-30 eagles in the air or in trees at any given time. A couple weekends ago I took my annual trip to the Samish Unit of the Skagit Wildlife Area and the eagles were thick in the air. At one point I counted 50 or more within a couple hundred yards.
http://wdfw.wa.gov/lands/wildlife_areas/skagit/unit.php?searchby=unit&search=Samish
You will need at least a 200mm lens to get really close up shots, and you can rent lenses at places like Glazer's in Seattle. I had a 300mm...