Isla Rasa and Isla Partida Norte, Baja California Sur
The announcement in April, 2005 by Cornell University and the Nature Conservancy of the rediscovery of the ivory-billed woodpecker in a remote wilderness of Louisiana gives hope for all endangered species. This massive and enigmatic woodpecker has been removed from the list of extinct birds…at least for now. Can we save it and others birds and mammals that are headed for the brink?
The ivory-billed has little to do with a tiny seabird-nesting island in the Gulf of California, but it symbolizes the struggle to survive by some birds, especially seabirds. Most seabirds nest on isolated islets. They seem to be fair game for extinction. In the past 300 years it is known that at least 90 species of birds have been pushed by various forces from the face of the Earth. Of these, almost all have been island-nesting birds, including, of course, a number of seabirds. Today we visited tiny Isla Rasa, which, except for changing resource uses and a concerted conservation effort, may well have added two species to the extinction list – the Heermann’s gull and the elegant tern. Up to 95 percent of the world’s populations of these birds nest on Isla Rasa. The discovery, refining and use of oil early in the 20th century made the mining of guano on this island uneconomical. The droppings of up to a half-million birds fed this mining venture through the late 19th and early 20th centuries. Up to 60,000 tons of guano were removed, destined for conversion into fertilizers and explosives. But with oil refining, these important products could be manufactured in other ways. One threat to the birds was gone.
The gathering of gull and tern eggs for the commercial market followed, however, quickly adding to the declining population. Rats and mice (devastating predators to any island bird colony) compounded the problem as they were brought unwittingly to the island by workboats. As few as 5,000 birds struggled to nest on Rasa when decisions were made to try to stop the decline. Egg collecting had been banned, and the eradication of feral rodents was successful by the mid 1990s. Public use was strictly controlled. Research studies were undertaken. Today, Enriquetta Vilarde, the island’s savior for the past 27 years and our guide for a walk among the nesting birds, proudly announced that 260,000 Heermann’s gulls, 180,000 elegant terns and 10,000 royal terns – almost half a million birds in total – are nesting on the island…an astonishing concentration. The first of the gull eggs were just hatching as we strolled, and the terns had assembled into their typical hyper-compacted colonies, nestled so close to each other that any predator would think twice before venturing into a wall of thousands of sharp bills. This was truly a spectacular sight. We will all have greater respect for seabird islands in the future.
Afternoon Zodiac cruises around nearby Isla Partida Norte filled the seabird picture a little more. Thousands of terns, gulls, pelicans and cormorants use this island as a base for their feeding forays. Later, a massive fin whale was encountered. Sleek, fast and deep diving, this cetacean eluded our efforts to approach. Our day ended as we slipped silently into pristine Bahia Don Juan, a perfect little cove on the central coast of the Baja peninsula. We would enjoy a restful sleep.
The announcement in April, 2005 by Cornell University and the Nature Conservancy of the rediscovery of the ivory-billed woodpecker in a remote wilderness of Louisiana gives hope for all endangered species. This massive and enigmatic woodpecker has been removed from the list of extinct birds…at least for now. Can we save it and others birds and mammals that are headed for the brink?
The ivory-billed has little to do with a tiny seabird-nesting island in the Gulf of California, but it symbolizes the struggle to survive by some birds, especially seabirds. Most seabirds nest on isolated islets. They seem to be fair game for extinction. In the past 300 years it is known that at least 90 species of birds have been pushed by various forces from the face of the Earth. Of these, almost all have been island-nesting birds, including, of course, a number of seabirds. Today we visited tiny Isla Rasa, which, except for changing resource uses and a concerted conservation effort, may well have added two species to the extinction list – the Heermann’s gull and the elegant tern. Up to 95 percent of the world’s populations of these birds nest on Isla Rasa. The discovery, refining and use of oil early in the 20th century made the mining of guano on this island uneconomical. The droppings of up to a half-million birds fed this mining venture through the late 19th and early 20th centuries. Up to 60,000 tons of guano were removed, destined for conversion into fertilizers and explosives. But with oil refining, these important products could be manufactured in other ways. One threat to the birds was gone.
The gathering of gull and tern eggs for the commercial market followed, however, quickly adding to the declining population. Rats and mice (devastating predators to any island bird colony) compounded the problem as they were brought unwittingly to the island by workboats. As few as 5,000 birds struggled to nest on Rasa when decisions were made to try to stop the decline. Egg collecting had been banned, and the eradication of feral rodents was successful by the mid 1990s. Public use was strictly controlled. Research studies were undertaken. Today, Enriquetta Vilarde, the island’s savior for the past 27 years and our guide for a walk among the nesting birds, proudly announced that 260,000 Heermann’s gulls, 180,000 elegant terns and 10,000 royal terns – almost half a million birds in total – are nesting on the island…an astonishing concentration. The first of the gull eggs were just hatching as we strolled, and the terns had assembled into their typical hyper-compacted colonies, nestled so close to each other that any predator would think twice before venturing into a wall of thousands of sharp bills. This was truly a spectacular sight. We will all have greater respect for seabird islands in the future.
Afternoon Zodiac cruises around nearby Isla Partida Norte filled the seabird picture a little more. Thousands of terns, gulls, pelicans and cormorants use this island as a base for their feeding forays. Later, a massive fin whale was encountered. Sleek, fast and deep diving, this cetacean eluded our efforts to approach. Our day ended as we slipped silently into pristine Bahia Don Juan, a perfect little cove on the central coast of the Baja peninsula. We would enjoy a restful sleep.
