As climate change, habitat loss and other challenges continue to put pressure on sensitive bird species, the more situations we’ll have like the one in San Diego Bay where Western Gull-billed Terns – an Audubon Watchlist species – are interfering with breeding colonies of California Least Terns and Western Snowy Plovers, both of which are protected under the Endangered Species Act. It’s a vexing situation for which easy answers aren’t likely to be found. The local U.S. Fish & Wildlife Service office has proposed addling 43 percent of the Gull-billed Tern eggs in the area, while the Center for Biological Diversity is petitioning to place the Gull-billed Terns on the Endangered Species List. Audubon California wants the best science-based solution for this problem, and is trying to put together a symposium to gather all the best information on the problem and arrive at a consensus solution that is best for these species.

The Gull-billed Tern is an Audubon Watchlist species, which carries no legal protections, but is nonetheless an important designation of conservation importance. The USFWS lists it as Bird of Conservation Concern and the California Department of Fish and Game lists as a Bird Species of Special Concern. Both the California Least Tern and the Western Snowy Plover are also Audubon Watchlist species, in addition to being on the Federal Endangered Species List. The California Least Tern is lists as Endangered, while the Western Snowy Plover is listed as Threatened.

The Western Gull-billed Tern only nests in two places in the Unites States, and these are at a number of sites around the Salton Sea and in San Diego Bay. Although this hasn’t been confirmed, it is possible that the bird is moving northward in response to climate change and habitat loss in Mexico, and due to habitat conservation efforts for the California Least Tern and Western Snowy Plover in San Diego.

Although data is somewhat anecdotal, it seems clear that the Gull-billed Tern is a serious threat to breeding California Least Tern and Western Snowy Plover. Volunteer monitors in San Diego report seeing whole fields of nests being decimated by foraging Gull-billed Terns. The USFWS is hoping that reducing the viability of the Gull-billed Tern eggs will reduce their foraging needs. The method it intends to use is to pour corn oil on the Gull-billed Tern eggs to render them unviable. The hope is that the Gull-billed Terns will continue to incubate the unviable eggs rather than set up new nests elsewhere.

In a perfect world, there would be enough breeding and foraging habitat for each of these species to prosper. That the Gull-billed Tern, the California Least Tern and the Western Snowy Plover have to compete is tragic. In normal circumstances, these species wouldn’t be in the same space. Before anyone sacrifices a population of a sensitive species to save other threatened or endangered species, it only makes sense to get all the relevant information on the table and have all concerned parties come up with a science-based solution that is the best for the birds.