Land Birds of the Galápagos



Nicolás Arnal
Letters and Sciences Major and College Park Scholars International Studies
July 5, 2000

On December 27, 1831, Charles Darwin left England with Captain FitzRoy of the H.M.S. Beagle, a vessel embarked on a surveying expedition around South America«s most southern tip. Charles Darwin was the first person to have explored and given importance to the species of life that inhabit the Galápagos Islands. He concentrated very much on studying certain birds to formulate his theories. On June 11, 2000, I embarked on my own tour of these Islands. My experience in exploring the Galápagos Islands was greatly influenced by the precedent set by Darwin and his ideas that were brought to the world by his life«s experience with exploration and land birds. Based on his findings in the Galápagos Archipelago, Darwin discovered what is known as the theory of evoltuion by Natural Selection which is of greatimportance to our undersatanding of the Galápagos ecosystem and to our the current understanding of the entire naturalworld. The land birds of the Galápagos Islands were central to this discovery. These birds were what Darwin once observedand studied many years before our arrival and it was amazing to observe these same birds which had been the basis for much of our current understanding of nature.

The focus of my assignment on the Galápagos Islands was to be the land birds. The sight of these islands managed to repel the first European explorers because they were inhospitable and profitless. Still, they are full of life, mystery, uniqueness, valuable lessons to human kind and beauty. The lessons can be learned from in books but to be there is certainly another story. The wisdom of creation seems to be within the Marine Iguanas (Amblyrhynchus cristatus) that greeted us with a smile and an indifferent gaze towards the crashing waves and the horizon under the bright mid day sun. One could speak volumes of the behavior or personalities of the animals that came across to the stupefied and warmed human visitors but oh yes, the land birds! Land birds!

The land birds of the Galápagos that we saw were:

Cuculiformes:
Smooth-billed ani Crotophaga ani

Falconiformes:
Galápagos Hawk Buteo galapagoensis

Galliformes:
Chicken (domestic)Gallus gallus

Gruiformes:
Common gallinule (aka moorhen) Gallinula chloropus

Passeriformes:
Yellow warbler Dendroica petechia aureolla

Hood mockingbird ,Nesomimus macdonaldi

Galápagos mockingbird Nesomimus parvulus

Galápagos flycatcher Myarchus magnirostris

Common cactus finch Geospiza scandens

Large cactus finch ,Geospiza conirostris

Warbler finch Certhida olivacea

Medium ground finch Geospiza fortis

Large ground finch Geospiza magnirostris

Strigiformes:

Galápagos owl Asio flammeus galapagoensis

The mockingbird was one of the first we came into contact with. Now there are four species of mockingbirds found in the Galápagos Islands. Of these, we saw the Hood Mockingbird (Nesomimus macdonaldi) and the Galápagos Mockingbird (Nesomimus parvulus). They both look quite similar and yet they belong to different species. The main feature that is present in these birds is their tameness. In this case, they are not tame because they have become dependant of human«s existence for their survival like dogs. They are still wild as ever but they are also tame in a sense because they are fearless! They fly and hop up to us just as they would in the presence of any other living creature. Now, the mockingbird is known to be aggressive as it does fight with other birds. Amazingly, their agressiveness does not change or lessen around humans. At first I thought they were angry, perhaps because we had invaded their ecosystem (as far as we know, harmlessly). As they chirped loudly and threateningly (for a small bird), I did not know then that they were only carrying on with their own behavior. That is what made them fearless. They would even land on some of us. They came this close to us not only because of their fearlessness but also because they associated humans with bottled water and desired handouts. Of course, we were not allowed to indulge them, because it would change their behavior and cause them to depend on humans, as dogs do.

I observed Darwin's Finches shortly thereafter. These are small, restless and very quick little birds. Their beaks are a guide to the evolutionary processes that occur on these islands. When observing the finches it was almost impossible to distinguish them by their species unless we asked one of our guides to tell us. The most subtle differences to our eyes mark the different species of finches. The reason why the finches are found on the Galapagos Islands is not certain, but we know that their ancestors came from the mainland of South America. When they got there, the food they found on the island such as endemic berries was not part of their original diet. In a very long process, these birds like many other animals, changed their feeding habits to eat what was there for them in order to survive. As different groups began to specialize on different foods, the shapes of their beaks began to differ as a result of natural selection.
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Many factors influenced the change within these animals which caused their distinguishing traits. For example, if one finch was competing against another slightly different finch to get food then the trait that was used to defeat the opponent was passed on to other generations, making them distinguishing traits of their species. As a result of this process, the beaks of some of today's finches, such as the Warbler Finch shown on the right, are slender while others, such as the Medium Ground Finch shown on the left, are deep. Some have long pointed ends while some have hard, short and rounded ends. It all depends on the feeding habits that they aquired and adapted to. Another factor that made telling them apart difficult was because depending on their breeding status, the color of these birds would change.
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We were soon to find as we walked across the Island«s trail in silent splendor and joy, that the larger land birds were also indifferent and tame. The larger land birds that we saw were the Galápagos Hawk (Buteo galapagoensis) and the Short-eared Owl (Asio flammeus galapagoensis). Also, the Galápagos Dove was seen on the dock of the Island of Espanola as well as many other places. The Galápagos Dove is related to the well known Mourning (Zenaida macroura), White-winged (Z. asiatica), Earted (Z. auriculata), and Zenaida (Z. aurita) doves.The Hawks we saw were found perching on large rocks. It looked as if they chose these rocks to signal their place in the food chain - at the very top. They look very poised and are handsome. When one sees the hawk take flight, it has a large wingspan and is a very skilled flier.

The Short-eared owl was very different from any other owl in North America. These owls are not nocturnal because their prey is active during the day which forces them to be active at the same time. This is contrary to other owls who feed on mice and rats that come out at night which is why they are nocturnal. The ancestors of these owls were once nocturnal on the mainland. Instead, these owls feed primarily on small sea birds such as storm petrels. What was amazing when viewing the Owl was that it sat among it«s prey of smaller birds while they went about their activity without concern for their safety. Its mysterious presence was aided by their heavy camouflage. They mimicked the brownish color of the soil as they casually perched among their prey.

These birds have been on the Island for some time, but a recent introduction that we also saw was the Smooth-Billed Ani. This is the largest black bird in the Galápagos. It has a long tail that hangs like a grackle«s and has shiny, elegant, black feathers with streaks of green. When they were introduced, they fed on the bugs that were flushed to the surface of grass by grazing animals such as cows. It is more rare to see these kinds of birds but we were fortunate. Because they have been in the island only for about ten years, the anis remain shy of humans. Except for the Anis, the Land birds of the Galápagos are all very tame and are successfully thriving in the ecosystem which has remained for the most part, undisturbed.

The Galápagos is a place one should not miss the oportunity to visit. The kind of communion that occurs when one steps on the Island in the presence of these fearless animals is very humbling and can very well be the most impacting experience of your life. I learned among other lessons that as animals we are also searching to continue, revise, expand and reinvent ourselves for the purpose of advancing our species in which ever sense of the word advance may mean to us.

Additional readings.

Grant, Peeter R., 1986 Ecology and Evoltution of Darwin's Fiches. Princeton University Press, Princeton.

Isabel and Antonia Castro, 1996 A guide to The Birds of the Galápagos Islands. Princeton University Press, Princeton.

Darwin, Charles. 1839 The Voyage of the Beagle, Bantam Books.