MANNS HARBOR, N.C. (AP) — It's time once again to slow down for birds on one bridge along North Carolina's Outer Banks.

From mid-July through August, state transportation officials lower the speed limit at dawn and dusk along the William B. Umstead bridge over the Croatan Sound at Manns Harbor.

The 20-mph-speed limit goes into effect to protect the more than 100,000 purple martins that use the bridge as their home before their annual migration to Brazil. The birds roost under the west end of the bridge at night. They depart at dawn for feeding before returning at sunset.

The state Transportation Department also activates flashing lights on the bridge.

To view the flock, check out Dare County's multi-purpose pier at the end of the bridge.