Let's say each foot of concrete has five nests, packed with mud and grass like adobe. 5280 feet times 5 is 26,400 nests. Each nests will hatch 4 to 7 eggs. Call it 5 hatches. Two adults plus five hatchlings comes to 158,000 birds.
And then you come to the next overpass, less than a mile away.
(click to enlarge)