I'm no expert at cropping. I do find the bottom distracting but also like the space there. You could clone the distractive greenery out? I would try either darking or cloning out the bh at the top left of the bird house also... but nonetheless, a very nice image! jano
Now that I've posted this I'm wondering if it would benefit from a crop - remove some of the background bricks from the left of the image and that gap between the bottom of the nest box and the bottom edge of the image. Hmmm.