Birds build all types of nests, many of which are intricately crafted into sturdy cups with sticks reinforced with mud. But pigeon nests, without an egg, are often overlooked as a random jumble of sticks - as if purposely half-assed. A nest that seems to mock other nests.
These nests may look useless to us but to a pigeon, it's not. When you think about it from a bird perspective, a nest needs to keep an egg from rolling away. In the case of most birds in rural areas with ample trees, that's a nice nest made with sticks and mud, but to a pigeon with concrete ledges and not much to work with, a pile of sticks gets the job done!