The annual effort to protect the Outer Banks’ purple martin flock begins tonight, as the N.C. Department of Transportation temporarily lowers dusk and dawn speed limits from 55 mph to 20 mph on the William B. Umstead Bridge.
The Umstead Bridge between the north end of Roanoke Island and the Dare County mainland is also locally known as the Old Manns Harbor Bridge.
From July through August, the west end of the bridge on Croatan Sound becomes home to more than 100,000 purple martins as they prepare for their annual migration to Brazil.
The birds roost under the bridge at night, departing at dawn to feed and returning at sunset. The flock is so large during its peak that it can be seen on radar.
Since 2007, NCDOT has partnered with the Coastal Carolina Purple Martin Society to educate the public about the flock and protect the birds and motorists.
NCDOT activates flashing lights and a 20 mph speed limit on the bridge at sunrise and sunset. The speed limit is monitored by law enforcement and allows motorists and birds safe passage across the sound.
Since the lights and speed limits were installed, the Coastal Carolina Purple Martin Society has seen a dramatic decline in bird deaths around the bridge.
As an alternative, motorists can use the Virginia Dare Memorial Bridge. Those wishing to view the flock safely can do so at Dare County’s multi-purpose pier at the west end of the bridge.
For real-time travel information, visit DriveNC.gov or follow NCDOT on social media.
This story originally appeared on OBXToday.com. Read More local stories here.