Q. What can you tell me about pigeons’ nests? We just moved into a fifth floor apartment and there’s what looks like some kind of a bird’s nest on the ledge around our balcony, except it has sticks and debris in it. If it is a pigeon’s nest, will they come back to the same nest this year?

A. A ledge high on a building would be a typical nest site for pigeons (also called rock doves) since their natural nest site is in caves or crevices on rocky cliffs. In urban areas, pigeons nest in a variety of sites, but rarely in trees. Their only requirement is a dry, protected area and a flat surface upon which to nest and perch. Nests are usually high up on roofs, ledges, eaves, attics, or steeples, or under bridges or overpasses.

The male starts the nest building process by sitting on the nest site and calling for a mate. Once he has attracted a female to the site, he begins the search for nest material, bringing a single twig at a time to the female who tucks it in around her. During the day, the male sits on the completed nest that usually contains one or two eggs. The female takes over nest duties at night. Pigeons can nest year round and can produce up to 10 young a year.

A pigeon’s nest is not a thing of beauty; it’s rather a mess. It’s made up of a conglomeration of sticks, small twigs, grass stems, pine needles, and debris — all piled together with a small cup depression in the center. Nests that are in continuous use are soon full of feathers and droppings. Unlike most other birds, pigeons do not remove the droppings of the young from the nest. The accumulated droppings tend to cement all of the nest materials together into a mound. And, yes, the pair usually does reuse the same nest site. They add new nest material right on top of the old sticks and droppings. Reused nests can even contain unhatched eggs and mummies of dead pigeon babies. Nests that have been reused for 3 to 4 years can be almost 8 inches high by 20 inches wide and can weigh more than 4 pounds!

You should discuss the problem with your property manager. You don’t want a pigeon’s nest on or near your balcony. The nest can harbor parasites such as bird mites and lice that can bite people. Droppings below the nest can deface the building, sidewalks, and cars, and large accumulations of droppings may contain disease organisms. Whoever removes the nest should wear gloves, and should discard the nest in a sealed plastic bag.

There are various types of deterrents and repellents that can be used to keep birds from nesting on the balconies or ledges of your building. A reputable pest control company that specializes in bird control can discuss the options.