Whose Tern Is It? A Tern Identification Guide
Written and Illustrated By Rachael
Spring at the Bolsa Chica Ecological Reserve (BCER) can be defined by the return of several species of tern from their wintering areas in Central and South America to perform their annual family duties. The tern species that nest in the BCER are at the heart of what the preservation and restoration of the Bolsa Chica wetlands is and has been all about. Terns, like other sand-nesting birds, have struggled to reproduce in an era where virtually all of Southern California’s sandy shores have been converted to the demands for human recreation. Our feathered friends needed a safe place to build their ground nests free of interference from trampling feet.
A primary reason for the formation of the Amigos de Bolsa Chica more than 40 years ago had been to ensure the wetlands and surrounding areas were spared from development and allowed to provide suitable breeding habitat for endangered species like the California Least Tern and threatened species like the Western Snowy Plover. The California Department of Fish and Wildlife (CDFW) constructed two small islands (North Tern Island and South Tern Island) within the muted tidal Inner Bolsa Bay, completed in 1978. The Lowland Restoration Project, completed in 2006, provided three additional protected nesting areas. The birds have enthusiastically responded.
Observers who come eager to witness these engaging creatures courting, flying, fishing and feeding their young are faced with a dilemma: it can be difficult to differentiate one species from another. There are Elegant Terns, Caspian Terns, Royal Terns, Least Terns and Forster’s Terns. Though not a part of the tern family, the Black Skimmer is a bird of similar size and shape that could be mistaken for a tern. On the following page is guide to the distinctive characteristics of each of Bolsa Chica’s terns to help alleviate confusion. Consider participating in the Amigos popular free monthly bird walk this spring to see if you can spot all the terns along the way. Bird Walks take place the last Saturday of each month at 9:00 am starting at the south parking lot in the BCER. One of the Amigos expert birders will be your guide. And since tern nesting areas are off limits to visitors, watch tern nesting activities from the Bolsa Chica Land Trust’s live eco-cam starting each April-May. http://bclandtrust.org.
Special thanks for tips on the best viewing spots for the terns to Kelly O’Reilly, Department of Fish & Wildlife Land Manager Bolsa Chica Ecological Reserve; Dr. Vic Leipzig, Golden West College Science Instructor (retired), past president Sea and Sage Audubon and Amigos de Bolsa Chica; Jerry Donohue, Science Instructor (retired), past president Amigos de Bolsa Chica; and David Beeninga, Orange County Naturalist.
Tern diet: Small fish including sardines, anchovy, pipefish and lizardfish make up most of tern chicks diet. Squid, small crustaceans and worms are also consumed.
Tern pair bonding: The male flies above while the female banks gently from side to side beneath him. On the ground a male tern will offer the female a fish during courtship or incubation in response to a call from the female almost identical to a young bird begging food from its parents. This courtship feeding most often occurs near the chosen nest site.
Flight and feeding behavior: Terns can be viewed in flight from all the public trails within Bolsa Chica. To pick terns out in flight look for body shape and size similar to small gulls. Seen from the ground tern bodies are mainly white with black head markings. Hunting terns tend to soar in languid circles from as high as 90 feet overhead, but usually much lower, carefully watching the water’s surface for small fish. When a tern spots potential prey, it tucks its wings and plunges head first into the water, often completely submerging.
California Least Tern
Where to see it: Nest Site 1 separating Inner Bolsa Bay and the Full Tidal Basin. Look through the chain link fence on the trail at the end of the footbridge. Least Terns can be seen sitting on nests and feeding young. Least Terns are often seen standing on the road located behind a south-facing gate along this fence.
EONS: The Eyes on Nest Sites program allows volunteers to record observations and collect data on the Least Tern and Western Snowy Plover nesting activities on Nest Site 1. Visit http://bolsachica.org/programs/research/eons/ for more information about becoming an EONS volunteer.
Where to see it: Forster’s Terns nest in the pickleweed located between the footbridge and North Tern Island within Inner Bolsa Bay. They often perch on the footbridge giving visitors an exciting close up view. Forster’s Terns fish at the tide gates separating Inner and Outer Bolsa Bay, and at the Pocket Marsh between the Wintersburg Channel and Bolsa Chica Mesa.
Where to see it: Elegant Terns nest on North Tern Island south of the footbridge in Inner Bolsa Bay. During some years, as many as 10,000 Elegant Terns arrive, and the overflow will take advantage of the Nest Site 1 just east of the north tern island separating Inner Bolsa Bay and the Full Tidal Basin. Elegant Terns fish at the tide gates as well as make frequent crossings of the Coast Highway to find fish in the ocean.
Feeding behavior: Early in the day these birds tend to fly alone. Later in the day, the birds heading out to feed often go in pairs. Elegant Terns will shake off excess water after diving.
Where to see it: Royal Terns nest amongst the Elegant and Caspian Terns on North Tern Island.
Where to see it: Caspian Terns nest on North Tern Island south of the footbridge in Inner Bolsa Bay along with the Elegant Terns, Royal Terns and Black Skimmers, though in far fewer numbers. They make their nests apart from the large groups of Elegant Terns.
Other notable characteristics: Caspian Terns are large, gull-sized birds, and their flight is characterized by distinctive somewhat labored rowing strokes. Known for their loud, screechy call.
Where to see it: Black Skimmers can be seen flying just inches above the water along the stretches of calm water in the Wintersburg Channel, and they also use both Outer and Inner Bolsa Bay to feed toward dusk. The number of Black Skimmers nesting at Bolsa Chica has decreased during the past few years and they are found in greater numbers at the Upper Newport Bay Ecological Reserve.
Feeding behavior: Skimmers are nocturnal feeders and begin to feed at dusk in small groups. They are highly agile as they fly just above the surface of the water holding their protruding lower mandible under the surface of the water while they fly. They capture food by touch; the upper mandible snaps down immediately when contact is made with a fish.