Pigeon or rock dove (Columba livia)

Size:
This exotic species is about 11″ long, and 13 ounces.

Signs of their presence:

The bird itself is the most obvious sign.

Sounds: Distinctive cooing, clicking as wing tips touch during take-off.

Droppings: May accumulate on rafters, building ledges, public areas.

Nests: Crude-looking platform nests of sticks, twigs, and grasses. Find them near dormer tie-ins (the joint where the dormer meets the roof), on building ledges, in steeples, attics, and lofts, on top plates of pole barns, on the girders of bridges, and on ornamental architectural features of classic buildings.

Common nuisance situations:

Time of year: Any time of year.

Droppings deface and corrode building facades and may kill plants. They’re unpleasant on park benches, statues and cars. Under certain conditions, the droppings can promote the growth of the fungus that causes histoplasmosis, an airborne disease that affects people.

Eat or contaminate stored grain.

One of their parasites, the northern fowl mite, is also a major pest of poultry. Other pigeon parasites (mites, fleas, lice) will bite people. Some of their parasites destroy fabric or stored foods.

Like other birds, pigeons may cause plane crashes.

May transfer disease from one livestock facility to another.

Disease risks: histoplasmosis, salmonellosis (food poisoning), cryptococcosis, pigeon ornithosis, encephalitis, and Newcastle disease, among others.
For more information:
http://www.nwco.net/08-AppendixBNuisanceSpecies/8-16-Pigeon.asp