The Kauai Endangered Seabird Recovery Project is conducting annual radar monitoring of two nocturnal seabird populations, the state Department of Land and Natural Resources said in a news release Monday.

The project coincides with the breeding season for the ‘a‘o (Newell’s shearwaters) and ‘ua‘u (Hawaiian petrels), the release said.

Two trucks will be used at 18 sites along Kaumualii and Kuhio highways and some county roads around the island, according to the release. The sites are where the seabirds are known to fly from the sea to mountainous regions where they breed.

The survey work will run through September, the release said. Monitoring will be conducted two hours after dusk when birds return to their burrows from the sea and two hours before dawn when seabirds fly out.