Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration
Office of Planning, Environment, & Realty (HEP)

Wildlife Protection

Keeping It Simple: Easy Ways to Help Wildlife Along Roads

Drivers on a North Carolina bridge slow down for migratory birds

On the William B. Umstead "Old Manns Harbor" Bridge spaning North Carolina's Croatan Sound near the Outer Banks, the smallest efforts are protecting the largest swallows in North America: purple martins. Every summer, 100,000 of these colorful migratory birds fly from Brazil to the western end of this bridge where they roost in group "apartment buildings" on the cables, girders, and I-beams under the bridge. Until 2007, thousands of purple martins were killed each year by fast-moving bridge traffic. In 2005 the Coastal Carolina Purple Martin Society documented 67% of the birds were hit at dawn by just 22 vehicles. Building a fence on the 2.8-mile-long bridge was impractical, so the Society worked with the North Carolina Department of Transportation to develop an alternative solution From July 1 through September 15 (nesting season for purple martins), and for a period of about 1.25 hours at dawn and at dusk, flashing speed-reduction signs appear on the 1-mile section of the bridge where the martins are roosting. The strategy is working. In fact, last year's documentation showed a 75% drop in purple martin deaths between 2004 and 2007.
--Mar 24, 2009

Phil Harris, (919) 715-1384 or

This photo shows a bridge with a sign in front warning motorists to reduce their speed when purple martins are leaving or approaching the bridge. A light at the top of the sign flashes at those times (dawn and dusk).
Photo by Alisa Esposito
A flashing sign at dawn and dusk was all it took to get drivers to slow down for the purple martins on this bridge

On or Near Bridges - North Carolina
Updated: 12/12/2012
HEP Home Planning Environment Real Estate
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000