Overview

Brief Summary

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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Biology

The Galapagos mockingbird is a cooperative breeder with territorial groups ranging in size from 2 to 24 birds (3). These intriguing and often complex social groups may comprise a single breeding female or several, with breeding pairs occupying individual nests but defending the group territory collectively. Typically contributing to the group dynamic are non-breeders (usually male off-spring from previous broods or failed breeders) that help to raise nestlings. Furthermore it is not uncommon for breeders to also help raise nestlings that aren't their own (2) (3). The nests are made from twigs and located low down on cacti or higher up on taller vegetation. Four eggs are normally laid and incubated over 12 to 13 days before hatching (2). Instead of flying, the Galapagos mockingbird is often seen running along the ground (6). It has a varied omnivorous diet comprising arthropods, fruit, nectar from cacti and other plants, small vertebrates, sea bird eggs and nestlings, and carrion (2). In addition, this species will remove ticks from the bodies of land iguanas, and populations on Santa Fe Island are known to occasionally drink blood from the wounds of living land and marine iguanas (2) (5) (7).
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Description

The limelight may have been stolen by Darwin's more famous finches, but it was the mockingbirds of the Galapagos that had the greatest early influence on his theory of Natural Selection. Of the four species of mockingbird that occur in the archipelago, the Galapagos mockingbird is by far the most widespread (3). The crown, nape and tail of this mockingbird are blackish brown, while the brown wings are partially tipped with white, and the throat, chest and belly are broadly white, with flecks of brown to the flanks (3) (4). Seven subspecies are currently recognised that differ slightly in overall size, colouration and markings (2) (3).
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Distribution

Range

Endemic to the Galapagos Islands, the Galapagos mockingbird is found on most of the major islands except those inhabited by one of the other three mockingbird species (2) (5). The different subspecies are found on separate islands: Mimus parvulus parvulus is found on most of the central islands including Santa Cruz, North Seymour, Isabela and Fernandina; M. p. personatus is found on Pinta Island; M. p. barringtoni is found on Santa Fe Island; M. p. bauri is found on Genovesa Island; M. p. bindloei is found on the islands of Marchena, Santiago and Rabida; M. p. wenmani is found on Wolf Island; and M. p. hulli is found on Darwin Island (3)
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Ecology

Habitat

Habitat and Ecology

Systems
  • Terrestrial
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The Galapagos mockingbird is found in a range of habitats including arid, coastal scrub, low Bursera woodland and mangroves (2).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s

Justification
Although this species may have a small range, it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
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Status

Classified as Least Concern (LC) on the IUCN Red List (1). Subspecies: Galapagos mockingbird Mimus parvulus parvulus, Pinta mockingbird Mimus parvulus personatus, Santa Fe mockingbird Mimus parvulus barringtoni, Genovesa mockingbird Mimus parvulus bauri, James mockingbird Mimus parvulus bindloei, Wolf mockingbird Mimus parvulus wenmani and Darwin mockingbird Mimus parvulus hulli (3).
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Population

Population
The global population size has not been quantified, but this species is described as 'common' (Stotz et al. (1996).

Population Trend
Stable
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Threats

The Galapagos mockingbird is relatively common throughout its range and its overall population is not thought to be declining. Consequently, of the four species of mockingbird that occur within the archipelago, only the Galapagos mockingbird is classified as Least Concern on the IUCN Red List (1). However, there is some speculation that a population of Galapagos mockingbirds may have existed on Pinzón Island, and been driven to extinction by introduced black rats before the first naturalists visited the island (3).
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Management

Conservation

There are currently no known conservation measures in place for the Galapagos mockingbird.
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Wikipedia

Galápagos mockingbird

The Galápagos mockingbird (Mimus parvulus) is a species of bird in the Mimidae family. It is endemic to the Galápagos Islands, Ecuador.

Systematics[edit]

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 Mimus genus, 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]

Description[edit]

On Santa Cruz

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]

Range and habitat[edit]

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]

Behavior[edit]

Food and feeding[edit]

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.[7]

Conservation and threats[edit]

On Santa Cruz

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.[8] 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.[9] 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.[10] Mockingbirds from the island of Genovesa are known to harbor the coccidian parasite Polysporella genovesae in their intestines.[11]

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 the 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.[12]

References[edit]

  1. ^ a b BirdLife International (2012). "Mimus parvulus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Arbogast, Brian S.; Drovetski, Sergei T.; Curry, Robert L.; Boag, Peter T.; Seutin, Gilles; Grant, Peter R.; Grant, B. Rosemary; Anderson, David J. (February 2006). "The Origin and Diversification of Galapagos Mockingbirds". Evolution 60 (2): 370–283. doi:10.1554/03-749.1. 
  3. ^ a b c Fitter, Julian; Fitter, Daniel; Hosking, David (2000). Wildlife of the Galapagos. Princeton, NJ, USA: Princeton University Press. p. 66. ISBN 978-0-691-10295-5. 
  4. ^ Jobling, p. 255.
  5. ^ Jobling, p. 293.
  6. ^ Swash, Andy; Still, Rob (2005). Birds, Mammals, and Reptiles of the Galápagos Islands: An Identification Guide (2 ed.). London, UK: Christopher Helm. p. 32. ISBN 0-300-11532-6. 
  7. ^ Buddenhagen, Chris; Jewell, Kelly J. (2006). "Invasive Plant Seed Viability After Processing by Some Endemic Galapagos Birds". Ornitologia Neotropical 17: 73–80. 
  8. ^ Vargas, Hernan (Spring 1987). "Frequency and Effect of Pox-like Lesions in Galapagos Mockingbirds". Journal of Field Ornithology 58 (2): 101–102. 
  9. ^ Fessl, B.; Couri, M. S.; Tebbich, S. (2001). "Philornis downsi Dodge & Aitken, new to the Galapagos Islands (Diptera, Muscidae)". Studia Dipterologica 8 (1): 317–322. ISSN 0945-3954. 
  10. ^ Kellogg, Vernon L.; Kuwana, Shinkai I. (30 September 1902). "Mallophaga from Birds". Proceedings of the Washington Academy of Sciences 4. Washington, DC, USA: Washington Academy of Sciences. pp. 457–499. 
  11. ^ McQuistion, Thomas E. (October 1990). "Polysporella genovesae n. gen., n. sp. (Apicomplexa: Eimeriidae) from the Fecal Contents of the Galapagos Mockingbird, Nesomimus parvulus (Passeriformes: Mimidae)". Transactions of the American Microscopical Society 109 (4): 412–416  – via JSTOR (subscription required). doi:10.2307/3226695. 
  12. ^ Slattersfield, Alison J.; Crosby, Michael J.; Long, Adrian J.; Wege, David C. (1998). Endemic Bird Areas of the World. Cambridge, UK: BirdLife International. p. 171. ISBN 0-946888-33-7. 
  • Jobling, James A. (2010). The Helm Dictionary of Scientific Names. London, UK: Christopher Helm. ISBN 978-1-4081-2501-4. 
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