After seeing Dolts macro shot's I was starting to think about buying a macro lens but an opportunity came up today and I think I'll get more use out of a longer lens than a macro.
Today I found a heron nest and did the best I could under the conditions. This was trhough one of my office windows using my 55-200 mm lens at 200mm. I may sound like I know a bit of what I'm saying but I really don't. It's printed on the lens

I also have an 18-105mm lens which I use most of the time.
So, this lady has built a nest at about eye level to me on the third floor. I can get a bit higher on occaision up to the roof with my tripod. I'm facing east. I think sunset will be best lighting. I would love to capture some good pictures of her raising her chicks.
The first shot is the uncropped and the second is heavily cropped.
So, how long a lens would you all recommend?