Cliff swallows are migratory birds that usually build their mud nest colonies on cliffs and rock overhangs. Since these areas are difficult to find in some parts of Iowa, the swallows often build their nests under concrete bridges on some of our state highways.

The cliff swallows are classified under the Migratory Bird Treaty Act of 1918 as migratory insectivorous birds, and are protected by state and federal regulations. It is illegal for anyone to take, possess, transport, sell or purchase them or their parts, such as feathers, nests, or eggs, without a permit.

Winters in Iowa take their toll on our bridges, and each spring it is necessary to wash the steel parts of some bridges to prevent corrosion. Power washers used to clean the bridges can sometimes wash away the nests.

A colony of nests under a bridge.

Last year the Department of Transportation learned that the cliff swallow nests need to be preserved. Since the nests are built to last and returning birds reuse the same nests year after year, the destruction of these nests could impact reproduction of the species.

The DOT has come up with a solution that will protect these nests, while cleaning and maintaining our bridges. Workers who wash the bridges are now required to look for these nests, and avoid any actions that will harm or destroy the nests. Since the steel portions of the bridges are the areas that need washing, the concrete parts where the nests are located can be avoided without affecting maintenance on the bridges.

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