Posted by: carlsafina | Wednesday, May 30 07

Seabird Treasures in the Sea of Cortez

Arriving on Rasa

Heerman's Gulls

Monday May 28, 2007

I’m aboard Lindblad Expeditions’ beautiful ship Sea Voyager for a much-anticipated week of travel in the Gulf of California, also known as the Sea of Cortez. The objective is simply to immerse ourselves—sometimes literally—in natural beauty. The ship is lovely, with about 50 passengers making for a diverse, intimate group. After leaving Loreto on the east coast of southern Baja Peninsula yesterday afternoon we steamed all night and part of the morning and awoke, still underway, among the islands of the upper Gulf.

Immediately the typical patchy nature of the sea was evident. Yesterday we left an area alive with pelicans and traveled through seemingly empty waters until we hit another area, swirling with currents and eddies, where we saw our first dolphins (mainly Long-beaked Commons and some Bottlenose), and more seabirds. We began seeing Blue-footed and Brown Boobies and lovely Heerman’s Gulls.

Heerman’s Gulls

For awhile, we had half a dozen Black Storm-petrals following us, and occasionally saw other tube-nosed seabirds: Sooty Shearwaters and Flesh-footed Shearwaters. In some spots we saw diving aggregations of thousands of birds, apparently feeding on sardines and anchovies pushed up by feeding dolphins. I glimpsed a Sperm Whale and a couple of Finback Whales. Every couple of hours or so, we’d come in and out of such concentrations of life.

We passed the islands San Esteban, Pedro Martír, San Lorenzo, and Tiburón. The latter is the Spanish name for the Gulf’s largest island and the homeland of the native Seri people. The Seri believe that their most sacred animal, Leatherback Turtle, created the island.

Our first stop was the famed seabird colony at Isla Rasa (Flat Island). Close to a million seabirds once nested here. Then, collecting thousands of years worth of accumulated guano (bird droppings, used in gunpowder and fertilizer), followed by heavy egg-taking, and finally by the pillages of rats that came ashore from the boats, nearly destroyed the birds. By the mid-20th century, they’d dropped to only about 5,000 birds. However, after entreaties by conservationists, the Mexican government declared the island a sanctuary. Conservationists poisoned all the rates, and birds again thrive. Continued presence of conservation workers, led for nearly 30 years by Enriqueta Velarde, helps safeguard the island. Competition by heavy industrialized fishing for sardines is an issue. The fish have collapsed several times partly through overfishing, and all go to feed livestock, rather than directly feeding people, at a loss of 90 percent of their energy value in the conversion of fish protein to mammal protein.

Nonetheless, the seabirds have rebounded now that the rats and egg-raiding people are gone. Nowadays nearly half a million birds nest at Isla Rasa. These include 95 percent of the world’s Elegant Terns and Heerman’s Gulls, making it important on the world conservation stage. Thousands of Royal Terns also nest here. Nearly All Elegant Terns

During non-breeding times they fan out from Canada to southern South America, with the Heerman’s Gulls sticking mainly to North America and the Elegant Terns going down to Chile. We saw many spotted eggs and spotted chicks as well as the throngs of adults. On the water were Eared Grebes—dozens—and a few Cravieri’s Murrelets. A few Ospreys are here too; the big fish hawks that have rebounded from the DDT era and are now so wonderfully common in many places. We see them near our house on Long Island all the time over the emerald salt marshes and bays, but it was a treat here to see them atop big Cordón cacti and to see how big they make their stick nests when they can keep working on them most of the year rather than migrating for long periods as do “our” birds up north.

Another favorite bird, the Peregrine Falcon, also nests here. Also a survivor of the worst DDT years, though wiped out in many places, Peregrines apparently hung on here because there’s no big agriculture nearby. We saw their nest site in a cliff grotto and enjoyed being visited by an adult and three flying young. I’m sure the terns and gulls don’t appreciate their presence, but with so many adults, not to mention chicks, the falcons take a small fraction of the seabirds. Peregrine FalconsIt was great to finally see an island I’d long heard of, and to experience the intensity of the place. I love seabird colonies because my own work has been so deeply involved in the study and conservation of seabirds for so long (I studied terns for my PhD). The sights, scents, smells, and sheer concentration of life are all thrilling. Amid the concern for nature we need to remember and learn from the successes—and Rasa Island is a success.



  1. I appreciate your different articles and obvious concern for the oceans. Do you ever find sea glass while out on your expeditions? i’m totally fascinated with the history and “beach archeology” behind these little gems. (see blog below for more on what i’m referring to)

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