Photos and Article By: Peter Knapp
Anyone visiting the Bolsa Chica Ecological Reserve the past three months has been treated to continuous aerial displays of white birds with black headdresses, heading for the open ocean and returning with fish. The Elegant Tern (Thalasseus elegans) has been nesting here in numbers never before seen at Bolsa Chica. My estimate is that there are 20,000 pairs (40,000 birds) that have nested successfully, producing another 10,000 young currently on site. This combines to be a total of 50,000+ birds! These numbers dwarf the number of other terns, including Caspian, Royal, Least, and Forster’s terns, which have been nesting along with the Elegants this year.
Why they are here in such large numbers can be traced to the failure of their primary nesting site in the Gulf of California, Isla Rasa. This site previously supported 90% of the breeding population, but has had no nesting for the past three years. Therefore, this site at Bolsa Chica and the Salt Works in San Diego have accommodated a large proportion of the entire breeding population of this species. I currently do not know of another major nesting site for this species. After a successful breeding season the Elegant Terns will disperse north along the Pacific coast before heading for their winter domain in South and Central America.
Some quick facts about Elegant Terns at Bolsa Chica consist of the following. The two nesting sites here are the North Tern Island and what is called Nest Site One, the long stretch of sand from the boardwalk (northern end) to the ocean inlet (southern end). This bird is a colonial nester, establishing a scrape in the substrate for one or two eggs [a scrape is a type of nest that consists of not much more than a shallow depression in the ground]. The nest is a beak’s length away from its neighbor so the concentration makes for a cacophony of sounds. This tern is a plunge diver for fish in the open ocean, where its food of choice is Northern Anchovy.