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.

History
  • Least Concern (LC)
  • Least Concern (LC)
  • Least Concern (LC)
  • Lower Risk/least concern (LR/lc)
  • Lower Risk/least concern (LR/lc)
  • Near Threatened (NT)
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