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.
The Galápagos mockingbird (Mimus parvulus) is a species of bird in the family Mimidae. It is endemic to the Galápagos Islands, Ecuador.
The Galápagos mockingbird is one of four mockingbird species endemic to the Galápagos Islands. These four are all closely related, and DNA evidence shows they likely all descended from an ancestor species which reached the islands in a single colonization event. When John Gould first described the species in 1837, based on specimens brought back from the islands by Charles Darwin, he named it Orpheus parvulus. However, because of the rules of binomial nomenclature, Orpheus was declared a junior synonym, and in 1841, George Robert Gray moved all of the Orpheus mockingbirds to the older genus Mimus. In 1890, Robert Ridgway created the genus Nesomimus for the mockingbirds found on the Galápagos Islands, and most taxonomists adopted the change. Recent DNA studies, however, show that the Nesomimus mockingbirds fall within the traditional genus Mimus, making the latter paraphyletic, so some taxonomists have moved them back into Mimus.[2]
There are six subspecies, each endemic to a particular island or islands:[3]
The genus name Mimus is a Latin word meaning "mimic",[4] while the species name parvulus is a Latin word meaning "very small".[5]
Like all of the mockingbirds found in the Galápagos, this species is long-tailed and relatively long-legged, with a long, slim, decurved beak.[6] The Galapagos mockingbird has a whitish stripe behind its eye, blackish-brown lores and ear-patch, and a broad white collar. The crown is dark brown, and the upperparts are greyish-brown with darker brown streaks. The flight-feathers are dark brown with two white wing-bars. It is whitish below, with a few brownish streaks on the breast and flanks. Its iris is yellowish, and the bill and legs are black.[7]
The Galápagos mockingbird is the most widespread of the mockingbird species found in the Galápagos; it is found on most of the major (and many of the minor) islands of the archipelago.[3]
Like the other mockingbirds found on the islands, the Galápagos mockingbird is an omnivore; it eats everything from seeds and invertebrates to eggs, baby turtles and Galápagos sea lion placentas.[3] Research suggests that the species may be an effective distributor of invasive plant species across the islands; it eats more fruit than did several tested species of Darwin's finches, but seeds that pass through its digestive tract generally remain viable.[8]
Studies show that avian poxvirus is a significant cause of nesting failure for Galápagos mockingbirds on Santa Cruz. Young birds appear to be more vulnerable than adults to the disease, and suffer high mortality when infected.[9] Larvae of the fly species Philornis downsi, which was accidentally introduced to the Galápagos, are known to attack Galápagos mockingbird nestlings; infestations often result in the death of young birds.[10] The Galápagos mockingbird is also host for a number of species of biting lice, including Docophorus galapagensis, Lipeurus languidus, Menopon insertum, Nirmus galapagensis and Nirmus vulgatus galapagensis.[11] Mockingbirds from the island of Genovesa are known to harbor the coccidian parasite Polysporella genovesae in their intestines.[12]
Although it has a relatively small range and its population has never been quantified, the Galápagos mockingbird is described as "common" and its population appears to be stable, so the International Union for Conservation of Nature assesses it as a species of Least Concern.[1] Its entire range falls within the Galápagos National Park, and is thus protected. However, like all native wildlife on the archipelago, it faces a number of potential threats, including habitat changes as the result of overgrazing, predation by various introduced species and fires.[13]
_-standing2.jpg)
On Santa Cruz
On Santa Cruz
The Galápagos mockingbird (Mimus parvulus) is a species of bird in the family Mimidae. It is endemic to the Galápagos Islands, Ecuador.
