I love Great Blue Herons! In Ohio we have a GBH Rookery that I visit every year in
February/March to start my 'bird photography' season.
You have a nice image here. I love the blue sky. You have the light on the face on
the GBH on the left, but the second one is in shadow.
The only suggestion I would have is, for these birds, unless they're in flight, go
vertical on your camera. Because you went horizontal, the GBH on the right
got caught off.
My rule for GBH are: Use horizontal to capture wing spans or flight. Use vertical
when they're stationary.
As far as the image you have here, I would still do a vertical crop due to the long
necks these birds have.
Nice opportunity. Vertical would have been the way to go here -- the bottom bird needs some "virtual space" for the rest of his body, even if he disappears into the nest. That would also have minimized or eliminated the large branches in the two lower corners, which are not adding to the image.
The image is quite underexposed, and it would be worth reprocessing to address that, just for practice.
The harsh midday light is difficult to handle -- a day with light clouds would be ideal.