Pigeons will breed on any convenient shelf, they prefer at least a foot above eye level and in a relatively shady and undisturbed corner which is why they tend to get 'underlooked' rather than 'overlooked'

(I once had to chase a couple out of my bedroom, they were checking out the top of our wardrobe for suitability.)
Gulls tend to breed in loose colonies quite far from human habitation (rocky coastland and offshore islands) and 'commute' to their feeding grounds, municipal dumps and littered beaches for example. We did a study on them for college and saw lots of the little cuties.. as chicks they're just as cute as chicken chicks with splodges and stripes. Then they moult through dull grey or brown speckled phases before they're as white as the parents.