Monday, May 28, 2012

Tour of Seymour Island

One of the highlights of our visit to Santa Cruz was the tour we booked to Seymour Island. Just north of Santa Cruz, across the Ithabaca Channel, is the island of Baltra. This is where the airport serving Santa Cruz is located, and it is also one place where American soldiers were stationed during WWII. (The soldiers called it "The Rock" because it is basically just a flat island made of blocks of hardened lava. There is some vegetation, but there was probably less vegetation sixty to seventy years ago.) Just north of Baltra is Seymour Island.

We took a bus across the island from Santa Cruz to the ferry dock at the northern end. We crossed part of the Santa Cruz highlands and were able to glimpse Los Gemelos, the large volcanic craters formed by collapsed gas bubbles in the lava. At the northern end of the island, we boarded our tour boat. We had a very international tour group comprised of: a French couple, a Korean couple, a Scot, a Swede, a Spaniard, a German, a Peruvian couple, and us. Our first stop was along a point at the tip of Santa Cruz Island for snorkeling. There was some confusion among the tour group regarding the snorkeling excursion (more about that in a separate post); however, some members of the group saw white-tipped sharks and others saw a manta ray. The visibility was surprisingly poor (perhaps because it had been raining recently), but I saw many surgeon fish and a few more parrotfish.

After snorkeling, we were given a hot lunch on the boat and made our way to Seymour Island. En route, we saw tropic birds and boobies nesting on cliffs. As the boat stopped in a small cove (where we transferred to the dinghy to go ashore), two huge Galápagos sharks circled around the boat and dinghy, affording us good views in the clearer water.

Seymour Island is uninhabited and is a nesting ground for great and magnificient frigatebirds. While these species are not endemic (native) to the Galápagos, it is rare to be able to observe them as closely as visitors to Seymour Island can. We took a hike around some of the perimeter and inland areas of the island. Here, we saw the frigatebirds in all their life forms: males, females, juveniles, and even a couple of chicks. Great frigatebirds have iridescent green coloration on the black feathers just behind their neck on their backs, while magnificient frigates have purple colored feathers. Females of both species have white chest patches.

Male great frigatebird showing iridescent green feathers
The most desirable male, in a frigate's eyes, is the one with a throat pouch as big as his body. (Sarcastic comment censored.) We had a very knowledgeable naturalist along as a guide, and he taught us that the males with the red throat patch inflated are still looking for a mate, while those with deflated pouches were already "married." Frigates, we learned, are also not monogamous; and after a chick is hatched, the male leaves the female alone to feed it while he goes off and mates with a new female. We were very excited to observe the mating ritual in which the male frigate "drums" on his throat patch to attract the female. The noise sounds exactly like a drum because the elastic throat pouch is tightened when inflated. We observed a female drawn into the sound of the male's thrumming and some initial overtures towards mating. However, the female eventually decided that the male was unsuitable and flew off. Our guide explained that even the males with the biggest throat pouches must first build a nest if they are going to be successful in attracting a female, and the frigate we were observing had no nest!

Male frigatebird with sizeable throat pouch
We were lucky enough to see one female sitting on eggs. The couple of chicks we saw were already four to six months old, but they still retained their fuzzy white down. We saw numerous juvenile frigatebirds, who are easily identified by their white heads. The picture below shows a juvenile sitting on a nest. Our guide explained that even though the juvenile is old enough to fend for itself, it is easier to sit on the nest and let mama feed it. It was very hard not to draw parallels between the behavior of frigatebirds and some human beings!

Juvenile frigatebird on nest
Finally, we learned about the unique feeding behavior of the frigatebirds. Our guide succeeded in changing my view of the frigates, who engage in a feeding strategy known as kleptoparasitism (stealing food from others). Frigatebirds have to steal their food because even though they are seabirds, their feathers have lost the waterproofing ability of those of other seabirds. Unlike boobies, pelicans, and albatross, frigatebirds cannot dive below the surface to catch fish. Thus, they must steal from other birds (and even from each other when a mother disgorges fish to feed her young.) We learned that the frigatebird is the lightest seabird (indeed, their appearance is very slender compared with the other birds mentioned) and that a pile of their bones would weigh about as much as the sum of their feathers.

While hiking along the island, we also saw our first Galápagos dove as well as many lava lizards.

Seymour Island is also home to a large number of terrestrial iguanas, which are an endemic species to the Galápagos---although not, as we learned, endemic to Seymour Island. Their unique ochre and rust colored scales/skin provide excellent camouflage for blending into the volcanic soils of the islands, where their chief predator---the Galápagos hawk---strikes from above.

Galápagos Terrestrial Iguana
The iguanas are threatened on Seymour because they are depleting their main food source, the Opuntia cactus. Since the terrestrial iguana was somehow transported to Seymour from another island, the flora of Seymour island has not co-evolved with the iguana. The Opuntia cactus on Seymour Island is the short form. It has not developed the adaptation of the hard trunk we saw in the tall cactus on Santa Cruz Island that makes it resistant to predation. If the iguana eats all the cactus on Seymour Island, it may not survive there.

Along the sea coast of the island, there are blue-footed boobies, marine iguanas, and Galápagos sea lions. The blue-footed boobies occupy hummock-shaped boulders in order to conduct their mating ritual. The female stands on the boulder while the male tries to get her attention. Some in our group were tempted to compare the ritual to human interactions, because the female booby stands there preening her feathers and looking bored while the male clamors for attention. As we observed in Mexico, the male then "dances" by showing her his feet. Our guide said she is looking at not only the size of his feet, but checking them for wounds and other imperfections, to determine whether he is suitable breeding material.

Blue-footed booby
As we made our way back to the boat at the end of the hike, we saw two swallow-tailed gulls. I would rate this tour, along with snorkeling at Las Tijeretas (on San Cristobal), as one of our best wildlife viewing experiences in the Galápagos.

The photos for this post will be added when we get to French Polynesia. Since the shutter on the good camera I was using broke, and the digital camera was experiencing condensation issues, all of the credit goes to Patrick for the wonderful photos in this post.

Posted from sea via HAM radio.

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