Hornbill was assigned to the mine force in the 12th Naval District.

She engaged in coastal sweeping of the main ship channel for magnetic and acoustic type mines.

After the attack on Pearl Harbor, her service became more valuable with the Japanese threat to U.S. West Coast sea traffic.

On the morning of 30 June 1942 Esther Johnson, a 208 ft 4 in (63.50 m), 1,104 GRT[1] steam lumber schooner on passage from Coos Bay, Oregon, collided with Hornbill in San Francisco Bay.

The crew was saved and a small amount of equipment was safely removed to the lumber schooner.