Black Skimmer, San Diego Bay National Wildlife Refuge

The last light of the day caught the underside of this black skimmer (Rynchops niger):

Black skimmer forages by flying over shallow water with its lower mandible dipping below the surface for small fish.
Image ID: 17420
Species: Black skimmer, Rynchops niger
Location: San Diego Bay National Wildlife Refuge, California, USA