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.

Description[edit]

On Santa Cruz

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.

Behavior[edit]

The Galápagos Mockingbird fights with other birds making it an aggressive bird, but it is known[citation needed] 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.

History[edit]

On Santa Cruz

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[edit]

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.

See also[edit]

References[edit]

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