Endangered and Sensitive Species

Project Materials

The California Least Tern and the Western Snowy Plover in Orange County

Even though the endangered California Least Tern and the threatened Pacific Coast population of the Western Snowy Plover prefer the similar beach habitats for breeding, they require different approaches for protection from predators and human interference. Historically, both of these species were abundant along the Orange County beaches. Both species nest in the sand by scraping a small depression with their belly and lining it with pieces of shells, stones, or fragments of nearby substrate. Least Terns typically nest colonially, while plovers are more independent. The eggs and chicks of both species are speckled, so the nest, eggs and young are extremely well camouflaged and can be easily stepped on. Both species breed during spring and summer, coinciding with heavy beach activity. Due to human disturbance, loss of habitat to development, and the increase of predators brought with urbanization, there has been a decline of useful breeding habitat for Least Terns and Snowy Plovers. The remaining breeding areas are fragmented, concentrated, and surrounded by development or human recreational activities, making management and predator control essential.

In Orange County there are only five breeding colonies of Least Terns: Bolsa Chica Ecological Reserve, Huntington State Beach, Upper Newport Bay, Seal Beach National Wildlife Refuge, and Burris Basin. The Snowy Plovers are breeding consistently only at Bolsa Chica Ecological Reserve. However, in recent years the plovers have nested on a few Orange County beaches. All of these nesting areas require close monitoring and management for success.

The Least Terns are migratory and are colonial nesters. They have an interesting defense system of their own against predators. Up-flights of large numbers of terns from the colony dart through the air, diving at the intruder, while calling loudly and even defecating on the intruder (docents need to wear hats). The tern parents make shallow dives from the air for small fish along the near waters of the coast and its estuaries to feed their young, making the adults and young vulnerable to fish abundance, and oil spills. They bring the fish back to the colony to their semi-precocial young. In a fenced-in colony, the young will wander about, but are restricted to the colony until they are able to fly over the fence. Low, fine meshed “chick fencing” keeps the chicks and pre-fledglings from wandering out where they could easily be stepped on or predated. These fences provide some protection from terrestrial predators and humans, but not from avian predators. Areas along the shore are also needed by the terns for the adults to teach the fledglings how to fish and for all of them to loaf. The beach location of the colony at Huntington State Beach is heavily used by people, constantly disturbing and distressing the birds. However, this colony has been one of the most successful in the state. The fledglings and adults disperse both north and south along the coast, possibly to find locations where disturbance is minimal, to have a place for the parents to begin teaching the fledglings how to “fish”, before migrating south.

The Western Snowy Plover is not migratory but disperses along the coast in winter. Our local beaches are home to Snowy Plovers from Orange County and other locations in the winter. This species faces even more challenges to a successful breeding season. They nest individually or in very loose colonies, with nests spaced further apart than the Least Terns. The young are precocial and run about within a few hours of hatching. They need to be able to leave their nest area in search of food, so an enclosed preserve such as those provided for some tern colonies would not be an option for the plovers. Their feeding method is to run and glean. They glean invertebrates from the wet or dry sand or wave-tossed kelp. Over the years, as the plovers became increasingly disturbed by people using the same habitat, they stopped nesting and raising young on Orange County beaches.

In Orange County, Snowy Plovers have nested successfully on protected habitats within the Bolsa Chica Preserve for decades. In recent years small numbers of Snowy Plovers have also made a return to the sandy beaches in Orange County. Officials have erected semi-temporary post & cable barriers around habitats areas preferred by plovers for breeding, called Plover Protection Zones (PPZs). Two of these PPZs are within a mile of the Least Tern Natural Preserve at Huntington State Beach, another is located near the P.C.H entrance to Bolsa Chica State Beach. Occasionally plovers’ also nest in front of and within the Least Tern Preserve and frequently use this area for many other activities, including foraging and rearing young plovers.

The Snowy Plover breeding population at Bolsa Chica Preserve is closely monitored. Whenever possible, when an active nest is found in Orange County, a wire mini-exclosure (“ME”) a small protective cage, is put over it. These MEs help reduce nest predation by preventing access by most predators, but have large enough openings to allow the plovers to get out. The plovers do not stay at the protected nest after the young have hatched. Both the adults and chicks are vulnerable to the abundant predators in the area as soon as they venture outside of the ME.