Gulf of California

Face-to-Face with Sea Birds in the Gulf of California
by -- May 8th, 2017

“Isla Rasa is like a fever dream.”

– Trevyn Toone, my fellow classmate on this field class

Even before we arrived at Isla Rasa, we were impressed by the increasing number of birds hovering over the sea, and waves and waves of bird calls. Our panga entered the island from the northern side, slowly making our way to the land of piled up volcanic rocks. It was low tide in the early afternoon, the water shining a beautiful, transparent turquoise and was so shallow that we jumped off the panga to walk through.

Isla Rasa on Google Earth: 28°49′26.12″N112°58′49.03″W

A close-up of Isla Rasa on Google Map

It was overwhelming at first—looking over, I could not tell how many birds are on this island. They are everywhere: nesting on the sandy flat, among the rocks, under the cholla cactus, The consistent bird calls and a strong smell of guano further enriched this very “birdy” experience. Enriqueta Velarde, a Mexican researcher on this island, walked out of her little cabin and greeted us.

The northern side of Isla Rasa

The existence of this whole island feels so unreal. This tiny volcanic island is almost flat and close to the sea level, standing in relative isolation in the Gulf of California. In the language of the indigenous Comca’ac, it is named “where pelican breeds”; however, brown pelicans (Pelecanus occidentalis) actually do not breed in the island. Instead, it is the nesting ground for over 95% of the world population of elegant tern (Thalasseus elegans) and Heermann’s gull (Larus heermanni). There are also a few other species that come to the island, such as black-vented shearwater (Puffinus opisthomelas) and black skimmer (Rynchops niger). “It is like the planet of Little Prince—we get a shearwater couple, several black skimmer couples, and an owl,” Enriqueta commented on the small number of other species.

Isla Rasa: In the front, Heermann’s gull and their nests. In the back, the white area is created by numerous elegant tern aggregating together. The elegant terns nest in groups to minimize their vulnerability to attack by predators such as yellow-footed gull (Larus livens); their close proximity to Heermann’s gull, whom yellow-footed gull does not bother with, also offers some extent of protection.

Enriqueta has been coming here to research the behavioral and reproductive ecology of Heermann’s gull every year since 1979. She shared with us the history of this island: it first attracted humans to come extract guanos for fertilizers. People constructed mount-like structures to aggregate guano. Bird eggs are also collected extensively by people from Baja California to make delicious bread. In 1964, it became the first bird sanctuary of Mexico. While only 15,000 nests existed during her first count in 1981, now, Enriqueta and other researchers count 50,000 nests.

Coming on this trip without expecting much about wildlife, I have seen a surprising diversity of shore and sea birds. On a day off from camping, we went for a sunset birding with research fellows from Prescott College field station. With the nice breeze and beautiful sunset, we saw clapper rail (Rallus crepitans), reddish egret (Egretta rufescens) and tricolored heron (Egretta tricolor) elegantly walking around the shore. The trip to Isla San Pedro Martir gave us a good view of not just sea lions, but also the nesting ground of blue-footed boobies (Sula nebouxii) and brown boobies (Sula leucogaster). On a boat ride, our captain Cosme made a sudden turn back and stopped to point out a small black dot on the wave to us—so there on the vast ocean, a tiny Craveri’s murrelet (Synthliboramphus craveri) siting on the waves, waiting for a chance to feed. Again and again, I was amazed by the diversity of birds I saw and their unique adaptations to the environment.

Isla San Pedro Martir: the white color of rock is created by years and years of guano

However, I have also learned how, in the post-guano eras, human disturbance continues to impact the bird population. For example, here on Isla Rasa, the rodents introduced by incoming boats have been destroying the eggs and still remain a problem; the overfishing of their food source, small, pelagic fishes like sardines, forces them to shift their diet to focus more heavily on shrimps and little squids. Both elegant tern and Heermann’s gull are near-threatened (NT) on the IUCN Red List. But it was looking at these birds, face-to-face, that made me start thinking about the importance of their conservation with more compassion and emotion. I looked at the birds hustling in and out the island, these small, brave souls fighting with the wind and waves with the hope to get dinner for today. I looked at the bird moms, opening their beak to cool off under intense sun, creating a precious shade for their eggs and chicks.

These sea birds have been fighting hard to survive. Feeling touched by them, I hope more people would take the time to look at them: how hard they fight to get their food, how strong and agile their wing beats are, and how they have evolved to survive on this vast, vast ocean.

Brown pelicans on Isla San Pedro Martir

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