By April and May most of the migrant birds have flown north to nest, while residents choose to nest on the refuge. Some nesting waterbirds on the refuge include American avocet, black-necked stilt, and Caspian tern. Western snowy plovers and their young chicks can be seen on the beach, in the dunes and along the edge of the saline pond. In the upland areas along the River Loop Trail, nesting barn and cliff swallows, common yellowthroat, and song sparrows are common. Birds such as gulls, herons, and egrets can be seen year round feeding and roosting on the refuge. Some non-breeding birds that visit the refuge are brown and white pelicans. As many as 1,400 pelicans have been seen roosting at the river mouth during the summer.