Day 7: Leon Dormido and San Cristobal - Sunday January 28th 2018
Overnight we travelled from South Plaza towards San Cristobal, the most eastern of the Galapagos Islands. We awoke near the rocky islet of Leon Dormido ("sleeping lion"), a few km off the central western shore of San Cristobal. We made an early morning panga ride tour of its perimeter and sea channels. Here we found several nesting Blue-footed Boobies and a colony of Great Shearwater - as well as the impressive rocks.
The two species of Frigatebird (Magnificent and Great) are closely similar. Magnificent averages larger, but there is considerable overlap, such that, after gaining experience, size would only be helpful to identify the largest Magnificents. The males are very similar - I could not distinguish them in flight. When perched they are said to be separable by the purple mantle sheen and brown or black legs of Magnificent, green sheen and reddish legs in great. A green sheen can be observed on the individuals facing away from us in the above image. At no time did I find leg colour a useful identification feature - the legs of the birds in the colony here appear to be brown. More on females and juveniles later.
We returned to the Beluga for breakfast and moved nearer the NW shore of San Cristobal. Here we were transferred, by panga, to Cerro Brujo beach. ("Cerro Brujo" translates as "Wizard Hill" and I believe this refers to the volcano well inland of the beach of the same name). We started by walking over a lava flow to view a nearby lagoon and then returned to walk along the beach. Before we got to the lagoon we encountered our first San Cristobal Mockingbirds and on the lagoon there were White-cheeked Pintail - the only common duck species on the islands. Along the beach we found Marine Iguanas, Ghost Crabs, Yellow Warblers, American Oystercatcher (an American tourist was overheard to ask if it was a penguin!), Lava Gull and Medium Ground Finches.
Although it is Darwin's Finches that are famous in association with his theory of evolution, he became aware of inter-island variations in the Mockingbirds first. The San Cristobal Mockingbird occurs only on San Cristobal. The differences between it and the more widespread Galapagos Mockingbird are
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minor. They are the same size and have the same structure. Perhaps the most obvious differentiating feature is the presence of a distinct malar stripe in the San Cristobal Mockingbird (the dark stripe between the dark cheek patch and the whitish throat); it also shows more prominent flank streaking - but this seems to be variable in both species and probably overlaps in extent. It is said to show a narrow white collar, but in the birds that I saw I found the collar to be just as broad as in the Galapagos Mockingbird, but less white. The iris of San Cristobal Mockingbird is supposed to be greenish (variable from reddish-brown to yellowish-green in Galapagos Mockingbird) - but I could not convince myself that any of the birds I saw had a greenish iris - they all looked brown to me.
I haven't said much about Darwin's Finches yet - these are so similar and hard to differentiate and played such an important part in Darwin's work, that they deserve a page all to themselves - see later.
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The marine iguanas on San Cristobal are of the subspecies mertensi. They have no clearly distinguishing features, being neither the largest, smallest or most brightly coloured race. Interestingly, the same race occurs on Santiago, but not on the (geographically) intervening island of Santa Cruz.
We returned to the Beluga for lunch and cruised on to the main town on San Cristobal - Puerto Baquerizo Moreno. I spent most of the trip trying to obtain some decent images of Elliot's Storm-petrel. Their small size and erratic flight made this a difficult task. Once again many blurred images were deleted.
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We saw three species of Storm-petrel on our tour. Elliot's was seen in small numbers almost daily, close to the shore and in the wake of the Beluga. They were easy to distinguish from Wedge-rumped (or Galapagos) Storm-petrel which has a much larger extent of white on the uppertail coverts extending almost to the tail-tip. Madeiran Storm-petrel is rarely found close to shore or in the wake of boats but was much more difficult to distinguish on the open sea. Elliot's can be distinguished by its small size, narrow white rump band extending onto the rear flanks, pale belly patch (sometimes known as "White-vented Storm-petrel" - but it is more the belly than the vent that is pale, and it is more a whitish smudge than the pure white of the rump) and feet extending beyond the tail. These last two features were difficult to observe in the field but show well on the images here.
Puerto Baquerizo Moreno is at the SW end of San Cristobal. As well as being the largest town on San Cristobal, it is the provincial capital of the Galapagos Islands. It's name comes from the first Ecuadorian president to visit the island during his presidency (in 1916). And it was the home of Rissel. |
Once ashore we took a bus to the Cerro Colorado Tortoise Reserve - one of several places on the islands where the Galapagos Tortoise is bred in sanctuary conditions, in an attempt to restore their much depleted populations. At the time of his visit, Darwin was informed that the native population could tell which island a tortoise had been collected from by the shape of its shell - this piece of information, crucial to his theory of evolution, returned to him much later, when he realised he had not recorded which islands he had collected his finch and mockingbird specimens from. Although it was nice to see the larger tortoises in a fairly open environment, the reserve had the feel of a zoo, and all the younger animals were confined in pens and cages. |
14 Subspecies of Galapagos Tortoise have been described, 3 of these are now extinct. Broadly they divide in two groups: dome-shelled - with shorter legs and necks, and saddle-backed - with the front edge of the carapace raised. Males are larger than females and have a concave ventral plate (plastron) (to facilitate mating) and a longer thicker tail.
On our way back towards the coast we stopped to ascend and then descend to the El Junco lagoon - one of very few permanent freshwater bodies in the Galapagos. Ostensibly we did this as the first (of four) inept attempts of our guide to find Galapagos Rail for us (or perhaps specifically , for me). I had little expectation that the manner of this attempt would be successful (essentially just hoping one would appear in the dense undergrowth) and the visit was scenically worthwhile without the pretence that seeing Galapagos Rail was its purpose. One thing I did notice which I found of particular interest was that the White-cheeked Pintails on the lagoon were diving. These ducks are in the genus Anas (along with Mallard, Wigeon etc), a genus of dabbling ducks - ie they would be expected to feed bums up head down at the water surface. I'm not sure if this feeding behaviour (ie diving) is unique amongst the ducks in this very large genus, but it is certainly unusual.