If you are doing a back yard perch you could get enough cable to run from your camera to your computer at your desk inside. Once you get the camera set up you could shoot from your computer. I like that idea.
However the concept of a shorter lens vs the longer I am not sure you would gain much at minimum focal distance. The bokeh would change, but I ran the numbers on the 300mm vs the 35mm II and your subject would fill the frame equally at the minimum focal distance. The DOF at equal apertures is near identical. The only advantage I would see is if you own the shorter lens and not a longer lens. The perspective with the DOF and the shorter lens might give some creative opportunity.