Land Birds

 


Mockingbirds

Although tortoises and finches are the organisms that most commonly come to mind when thinking of Darwin, the Galapagos, and evolution, it was the mockingbirds, or mocking-thrushes as Darwin called that first drew Darwin's attention to the strange diversity of species within the archipelago.

"...the different islands probably have their representative species or races of the Amblyrhynchus, as well as the tortoise. My attention was first thoroughly aroused by comparing together the numerous specimens, shot by myself and several other parties on board, of the mocking-thrushes, when, to my astonishment, I discovered that all those from Charles Island belonged to one species (Mimus trifasciatus); all from Albemarle Island to M. parvulus; and all from James and Chatham Islands...belonged to M. melanotis."

There are actually four species of mockingbirds, distributed as follows among the islands:

Genus and species


 Common Name


 Distribution


  Nesomimus trifasciatus

Charles Mockingbird  Champion & Gardner-near Floreana

  Nesomimus macdonaldi

 Hood Mockingbird  Espanola

  Nesomimus melanotis

 Chatham Mockingbird  San Cristobal

 Nesomimus parvulus

 Galapagos Mockingbird all other islands except Pinzon 

The populations of the Charles mockingbirds on Champion and Gardner-near Floreana are survivors of a main population on Floreana. Floreana was the first island to suffer a human population and the mockingbirds likely became extinct as a result. Darwin reported it when he visited in 1835, but it hasn't been seen since. Champion and Gardner-near-Floreana are satellites whose populations still thrive.

It is not surprising that Darwin was surprised that similar islands, within sight of one another, would have different yet related species, but the distribution of mockingbirds correlates well with the distribution of other Galapagos species. Lava lizards, for example, have a very similar distribution. Floreana, Espanola, and San Cristobal, which are isolated by wind and current if not distance, each have their own species. A fourth species covers all of the central islands (with the notable exception of Pinzon, which has its own species; there is not resident mockingbird population). Finally, the outer islands of Pinta and Marchena each has a unique species, bringing the total number of species of Lava lizards to seven.

The four mockingbirds, all of the genus Nesomimus, seem to be descended from the mainland genus Mimus, most probably Mimus longicaudatus the Ecuadorian Long-tailed Mockingbird. Of the four species of Nesomimus, the Galapagos and Hood mockingbirds are most frequently encountered and most easily distinguished from one another. Their are differences in plumage, but the most obvious physical difference between the two is their beak. The Hood mockingbird has a much longer, more curved beak than the Galapagos mockingbird 's.

There is also a pronounced behavior difference. The mockingbirds, like most Galapagos species, are quite unafraid of people and very curious, but the Hood mockingbird is extremely aggressive. It is not uncommon for them to land on a visitor's head and they will explore any unknown object, always looking for food or drink. To tourists they are amusing, but to scientists who work in the Galapagos, they can be a major nuisance.

The Chatham mockingbird is somewhat intermediate in appearance, and is not seen that often, most especially because most tourists do not visit San Cristobal, and those who do generally do not go in search of them. It is possible to see the Charles mockingbird, but only with careful planning. Visitors are not permitted on Champion,but it is possible to navigate around the island in a dinghy and observe from the water. I have tried this on several occasions and seen them, but only from great distance, and never in clear camera range.

One of my favorite spots in the Galapagos is a small indentation in the mass of salt bush (Cryptocarpus) that forms the back end of the beautiful sandy beach at Gardner bay on Espanola. I love to walk in, and sit quietly while everyone else cavorts on the beach, snorkels, or plays with the sea lions. There, in what I call the "magic spot" patience is rewarded when all of the land birds -- finches, doves, flycatchers, and of course mockingbirds -- gather. It is during those quiet times when I can sit and observe, reflect, and commune that I feel the most connection to Darwin:

 "The distribution of the tenants of this archipelago would not be nearly so wonderful, if, for instance, one island had a mocking-thrush, and a second island some other quite distinct genus....But it is the circumstance, that several of the islands possess their own species of tortoise, mocking-thrush, finches, and numerous plants, these species having the same general habits, occupying analagous situations, and obviously filling the same place in the natural economy of this archipelago, that strikes me with wonder."



    for more info, contact Dr. Robert Rothman: rhrsbi@rit.edu