What happens when you create a gap on your board in Wingspan?
there's options to create empty spaces on your board.

No. From the FAQ:

How do I play a bird on top of a sideways bird?
Some birds like the European Roller allow you to place the card sideways on your player mat, filling two spots. If you then play a bird like the Common Buzzard on top of a sideways bird, the Common Buzzard would also be placed sideways, completely covering the sideways bird.