© 2004 Thomas Anderson ...Science Art-Birds

Title: Moonstone Beach
Species: Heerman's Gulls (Larus heermanni)
Artist: Thomas Anderson (for further information, click on the artist's name)
Image size: 24" x 36"
Media: oil on canvas
Date: 2004
Current Location of the Image: studio of the artist

The artist notes: "These Heerman's Gulls are loafing at Moonstone Beach, which is located on the often foggy central coast of California near Cambria. They have traveled north from their island breeding colonies in the Gulf of California--primarily on Isla Raza--to winter, and are seen here in non-breeding plumage." [Second-winter?]

Anderson explains that Heerman's Gulls are unique among North American gulls both in appearance and in their "reverse" migration pattern, which takes them from their breeding colonies the Gulf of California to wintering sites along the North American coast from San Diego, CA to Vancouver Island, British Columbia.

In 1964, the Mexican Government declared Isla Raza a wildlife sanctuary and limited access during the breeding season to reserachers and wardens. In response, the worldwide Heerman's population has grown from 55,000 pairs in 1975 to 150,000 pairs, and might account for several recent nesting attempts along the California coastline. But, Heermann's Gulls have been little studied.

What researcher do know is that these birds remain at risk, not only because their breeding colonies are concentrated in a single area (Isla Rasa hosts perhpas 90 percent of the population) and therefore potentially at risk to disturbance and the expansion of Yellow-footed Gulls that prey on eggs and young, but also because of the threat of pesticide contaminants, direct competition with humans for Pacific sardines, and depredation by introduced black rats at their breeding colonies. Researchers would like to know more, especially about their foraging, energetics, calls reperatoires, and general breeding biology--especially beyond Isla Raza.