Isabela—Tagus Cove

Route map

Isabela

On the west coast of Isabela, across the Bolívar Chanel from Isla Fernandina, Tagus Cove (Caleta Tagus) has offered safe anchorage for more than 300 years because of its sheltered situation.  Pirates and whalers were among the earliest arrivals, as evidenced by names of ships inscribed on the cliffs by the landing. (The photo on the right is of a small cave above the landing.  Click on the photo to see a larger version with the faint etchings on the rocks).  The cove was named after an English warship that passed by in the early 1800s, perhaps looking for giant tortoises for fresh meat.

Thursday, May 16, morning

The walk from Tagus Cove to the viewpoint on the ridge wasn’t very long—just over 1 mile.  (See above photo from the National Park Web site.)  But it was moderately steep, gaining roughly 500 – 600’ in altitude, without much shade.  So we headed out before breakfast, to avoid the heat that would take over as early as mid-morning.  Coffee and tea awaited us at 6 a.m., and crackers and cookies served as a “pre-breakfast” snack.  At 6:30, we headed for the pangas.

The dry landing provided no problems for us (below, left) and the path was a combination of gravel, cinders, steps, and stones.  A fledgling finch (my best guess—a Small Ground Finch—right) watched us pass.  (Click on any photo to see a larger version.)  You can tell it’s a young bird because of the gape flanges—the lighter edges at the corners of its beak.  When begging for food, a nestling’s gape flanges provide almost a target for the adult bird to stuff food into the baby’s mouth.  These flanges fade as the bird matures—so this bird probably hadn’t been out of the nest for too long.

As we started out, Carolina picked up a long branch and held it casually in the air as she walked along.   After a few minutes, she called us over to look at the stick.  On it—a zigzag spider (Neoscona cooksonii; photo on right from my field guide).  Several genera of spiders throughout the world are called “zigzag” spiders, because the females weave a zigzag pattern into a portion of their webs.  (Although not a photo we took, you can get a sense of the zigzag weavings in the photo to the left.  Again, click on the photo to get a better look.)  N. cooksonii is renowned for building her web across trails in arid areas, which is why Carolina suspected she might pick one up as we climbed the path.

The path took us to a lovely spot overlooking Darwin Lake—a brackish lake contained within a tuff cone,a structure made up of consolidated ash following an eruption (photo below).  At about 30’ deep, it contains no fish or other wildlife.  Seawater filters in through fissure in the cone; rainwater collects in the lake as well.  A truly lovely view, especially with the elegant Mary Anne in the background.

From the ridge viewpoint at the end of the trail, with Volcán Darwin to the north,  Palo Santo trees stretched as far as the eye could see in every direction.  Palo Santo trees are leafless much of the year, although the trees here had some leaves.  The actual bark of these trees is dark—purple or brown; however, lichen cover the bark and give it its characteristic gray color.  The name (“holy stick”) may refer to the fact that it leafs out around Christmas or to its use as incense in churches on the mainland.

At this viewpoint, Carolina also pointed out a distant mangrove swamp, one of the very few housing the endemic Mangrove Finch.  (The photos below were taken as we traveled past the spot on the western shore of Isabela later that afternoon.)  Only about 100 birds remain, only on Isabela—and therefore, only 100 birds on the planet—making this species the most endangered species not only in the archipelago but in the world.  They used to live on Fernandina too, but those birds are now gone.  Researchers attempted to relocate 4 birds from Isabela back to Fernandina; 2 returned to Isabela and 2 just disappeared.  Some older publications state that the only species of “Darwin’s finches” to have a single-island distribution is Floreana’s Medium Tree Finch.  However, since the Mangrove Finch appears not to inhabit Fernandina any more, the archipelago now has 2 species that can claim this dubious, marginalized, vulnerable honor.

As we headed back down the trail to the landing, Carolina pointed out a finch in a tree a ways back from the trail, searching under loose pieces of bark—a Woodpecker Finch, a congeneric of the endangered Mangrove Finch!  (For once, I’ll recommend that you don’t click on the photo to see a larger version.  You’ll just have to trust me that the photo on the left is indeed a Woodpecker Finch.  The camera thought we were interested in the branches in front of the bird…)  These 2 species and the 3 species of tree finches are the world’s only existing members of the genus Camarhynchus.  This finch is easiest to identify through its behavior rather than its plumage.  Unlike the ground finches, which forage out in the open searching for seeds on the trails (and are sooooo easy to photograph), the Woodpecker Finch eats insects and larvae more so than seeds.  The Woodpecker Finch is perhaps best known among the “Darwin finches” for its use of small twigs to find larvae in crevices.  In fact, it can even adapt a twig or a cactus spine to better fit a specific purpose.  One report stated that, in some seasons, the Woodpecker Finch uses some kind of tool to obtain up to 50% of its diet—thereby surpassing the chimpanzee, which is the most proficient non-human primate tool user.  This species has evolved to fill in a niche occupied by woodpeckers on the mainland, since it doesn’t have the long, extendible tongue that woodpeckers have for grabbing such invertebrates.  Therefore, the Woodpecker Finch has adapted by using tools to probe into tree nooks and crannies.   (Mangrove Finches are alleged to use tools in this way too.)

Continued on p. 2; click below.

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