Teehjaeh57, with camera equipment there are a lot of different ways to get you what you want, but there are trade offs you will have to accept. A high end lens to shoot 4" birds at 70 feet, that is probably going to be heavier and more costly than you may be comfortable with. I would suggest an alternate idea of getting a little closer and using cover such as tent. The cost of a quality lens shooting at 20 feet is a lot less than 70 feet. And get a quality tripod, worth every penny.
