Doves enjoy the feeling of being grounded, even if they are doing it in the air. Since these birds are known for making nests that require support, they often build their nests on platforms or other stable structures that can provide support and protection. In order to comfortably build their nest, they will look for an elevated and compact platform of some sort, like a windowsill or horizontal support beam.
The important part is that they might have somewhere safe and secure to bring together all of the plant pieces that they like to use. If you want to appease the local doves, give them a space that has a platform and is somewhat covered at the same time.