The apparent diversification of Galapagos mockingbirds (Nesomimus) among the Galapagos Islands inspired Darwin’s initial conception of adaptive radiation (in which diverse forms arise through many generations from a single ancestor via local adaptation). Arbogast et al. (2006) used mitochondrial DNA (mtDNA) sequences to infer phylogenetic relationships among the various mockingbirds occurring across the Galapagos Archipelago. Their results indicated that the Galapagos mockingbird species and their inferred ancestor form a monophyletic group (i.e., a natural group consisting of an ancestor and all its descendants), suggesting a single colonization of the archipelago followed by diversification. Their analyses also indicated that Nesomimus is nested within the traditional mockingbird genus Mimus. Based on this result, use of the genus name Nesomimus is falling out of favor, with all the Galapagos mockingbirds being included in the genus Mimus (e.g., Arbogast et al. 2006; Lovette and Rubenstein 2007).
The southeast quadrant of the Galapagos Archipelago contains three species, each endemic to a single large island: the San Cristobal Mockingbird (N. melanotis) on San Cristobal; the Espanola Mockingbird (N. macdonaldi) on Espanola; and the Floreana Mockingbird (N. trifasciatus), which is now restricted to two islets adjacent to Floreana (efforts to recover this endangered species through appropriate tranlocations have received some guidance from analyses of the DNA of mockingbird specimens collected by Darwin on Floreana in 1835; see Hoeck et al. 2010). A fourth species, the Galapagos Mockingbird (N. parvulus), inhabits most other islands in the archipelago. Arbogast et al. found that most mockingbirds from the central and northern portion of the archipelago, which are currently considered conspecific populations of N. parvulus, do indeed appear to be closely related. However, based on their mtDNA analysis, Arbogast et al. found that N. parvulus on Genovesa (which are often recognized as N. parvulus bauri, e.g. Cody 2005) may actually be more closely related to N. melanotis and N. macdonaldi than they are to N. parvulus on other islands (the authors note that this possibility must be investigated further with multilocus data from the nuclear genome).
An intriguing study of the response of Marine Iguanas (Amblyrhynchus cristatus) to alarm calls of N. parvulus found that these lizards increase anti-predator vigilance behaviors when exposed to N. parvulus alarm calls. This is apparently the first known example of a non-vocal species associating the auditory alarm signals of another species with the threat of predation (in this case, the potential predator is often a Galapagos Hawk [Buteo galapagoensis]) (Vitousek et al. 2007).
Cody (2005) provides a detailed summary of the biology of this species.
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The Galápagos Mockingbird is easily spotted on the Galápagos Islands due to its feathers which are streaked brown and gray, long tail, and smaller size, and black, angled beak. The bird has a darker color than other mockingbirds on the islands causing it to blend in with the coral sand of the islands that it mainly inhabits. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry shrubland. Like other mockingbirds it is omnivorous, but it is more predatory than the related species in South America. It preys on small lava lizards, insects, centipedes, carrion, seabird eggs, and young finches. It will also devour any food left out by people visiting the islands. It has a very clear call that sometimes varies, but unlike other mockingbirds, Galápagos mockingbirds are not mimics. Although they can fly, they are known to be seen running around more than flying which has led to comparisons to road-runners.
The Galápagos Mockingbird fights with other birds making it an aggressive bird, but it is known as a bird that does get quite close to people, seeming fearless. They are unique in that when the hatchlings are born, the juveniles help out with raising them. Another unique living style is that while living in communities, the oldest male holds responsibility for providing food for and taking care of the young ones. The fact of whether he is the parent does not matter, and he is usually referred to as the alpha male of the group.
The birds build their nests in trees and cacti. About two or three females in each group breed at a time, but it can range from one to several breeding females in groups sized from 2 to 24. The males in the groups that aren’t breeding are “helpers” and help the breeding females, but the females that are not breeding, hardly ever help out. This helping shows the influence of kinship.
The Galápagos Mockingbird descended from the Ecuadorian Long-tailed Mockingbird. There are three other species of mockingbirds found on the Galápagos Islands, but the Galápagos Mockingbird is the first one that was found in Darwin’s trip to the islands in 1835. They had a greater influence than any other animal on Darwin’s theory of evolution when he arrived there because it was the first species that Darwin noticed distinct differences among when he looked from island to island. This is what caused more species to develop. The Galápagos Mockingbird is the one seen about the archipelago more than any other mockingbird. They are seen among the islands of Santa Cruz, Santiago, Isabela, Fernandina, Santa Fe and Genovesa, but is thought to have originated in San Cristobal. Although they seemed alike on both the islands of San Cristobal and Isabela, they seemed different on Floreana and Santiago.
Adaptation to the climate
Because of the climate that the Galápagos Mockingbirds live in, their social organization is quite different from that of others. Their mating structure changes depending on which gender outnumbers the other. When there are more males than females, it is monogamous, and when there are more females than males, it is polygynous. Joint nesting occurs quite frequently during the polygynous time. Their breeding seasons go with the times of year. During El Nino, they breed a lot, and during the times of drought, they don’t breed at all. Although a lot of breeding takes place during El Nino, it also causes a lot of deaths in the mockingbirds because of all of the water. This change in weather is the main reason why their population fluctuates so much.
- Arnal, Nicolas. “Land Birds of the Galapagos.” Galapagos 2000. 5 July 2000. 4 March 2008.
- Curry, Robert (6 September 2007). "Darwin’s Mockingbirds: The endemic mockingbirds of the Galapagos:". Retrieved 17 April 2008.
- Kendall, Meredith. “Survivor: The Evolutionary History of the Galapagos Mockingbirds.” Darwin, Evolution, and Galapagos. 7 Oct 2002. 4 March
- Vaca, Ernesto. Galapagos. Zipcode Zoo. 29 Sept 2005. 4 March 2008.
- Galapagos Natural History. Galapagos Online. 1 March 2008.