Nest:

Now builds extensively on man-made structures, in recesses of rock ledges, caves, and especially on girders under bridges or trestles over water.

The nest is a cup of mud and moss, lined with grass and feathers; it is about 4-1/2 inches in diameter.

Sometimes will build a second nest or even a third, fourth, or fifth on top of an old nest in subsequent years.

Host to cowbirds.

Eggs:

3 - 8, commonly 5, white, although a few may be spotted with brown about the larger end.

Incubation:

14 - 17 days; young leave nest about 15 - 16 days after hatching; 2 broods, sometimes 3, in a season.