Overview

Brief Summary

Biology

In comparison with the mockingbirds occupying the other islands, the San Cristobal mockingbird is somewhat shy (3). Much of its time is spent foraging through leaf litter for arthropods such as grasshoppers and crickets. Fruits and berries are also taken from low vegetation, and on occasion it can be seen darting amongst the marine iguanas, picking off their ticks (2) (5). Unlike the other mockingbird species, the San Cristobal mockingbird is not known to breed cooperatively (2) (3) (5). Instead the relatively large, three to five hectare territories are normally occupied by just a single pair, sometimes accompanied by another adult. Breeding takes place from January to April, with each breeding pair building a bulky twig nest, high up in the crotch of a tree, out of reach of introduced predators (3) (5). Incubation of the two to five eggs is left to the female, but both parents share feeding duties (5).
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Description

One of the first animals Darwin encountered when he arrived in the Galapagos in 1835 was the San Cristobal mockingbird (3) (4). His subsequent discovery of two more species of mockingbird, each occupying a different island and differing subtly in appearance, provided tinder for the incendiary theory of Natural Selection (3). The San Cristobal mockingbird has a somewhat streaked, greyish-brown crown and upperparts, and an almost white throat, chest and belly. Prominent black lores mark the base of its relatively short downwards curving bill and black ear patches are conspicuous below its amber to reddish-brown eyes. The loud and melodious, territorial song of this species is typical of all the Galapagos mockingbirds (2) (5).
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Distribution

Range Description

Mimus melanotis is endemic to the island of San Cristóbal in the central Galápagos islands, Ecuador (Sibley and Monroe 1990). Its population has recently been estimated at c.8,000 individuals, on the basis that it occupies c.25% of the 552 km2 area of the island, with occupied areas holding approximately 0.6 birds/ha (R. Curry in litt. 2005).

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Range

San Cristóbal I. (Galapagos Islands).

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Range

Endemic to San Cristobal Island in the central Galapagos (2) (6).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
It occupies a wide range of habitats from lowlands up to the island summit at 715 m, including arid open lowland scrub, mangroves, scrubby woodland with scattered trees (Bursera spp.) and arborescent cacti (Opuntia spp.), low woodlands of introduced guava (Psidium guajava) and taller patches of forest. It tends to avoid dense lowland forest, taller, wetter woodland, grassland and urban areas (Cody 2005). The species forages on the ground for arthropods, also taking fruit and berries and occasionally picking ticks (Acarina) off marine iguanas (Amblyrhynchus spp.). It breeds in January to April, apparently not cooperatively, in contrast to other Nesomimus spp. (Cody 2005).


Systems
  • Terrestrial
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The San Cristobal mockingbird is found in a wide range of habitats all over the island, from mangroves and arid lowland scrub, to taller forest patches and stands of arborescent cacti. However, it does tend to avoid dense lowland forest, wet woodland, grassland and built up areas (2) (5).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1ab(ii,iii,v)

Version
3.1

Year Assessed
2013

Assessor/s
BirdLife International

Reviewer/s
Butchart, S.

Contributor/s
Curry, R., Tye, A., Vargas, H. & Wiedenfeld, D.

Justification
This species is classified as Endangered because it is likely to be declining within its very small range on a single island, as a result of habitat degradation and the impact of alien invasive species.


History
  • 2012
    Endangered
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Status

Classified as Endangered (EN) on the IUCN Red List (1).
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Population

Population
R. Curry (in litt. 2005) estimated that this species occupies c.25% of the 552 km2 area of San Cristobal, i.e. 138 km2. The density of birds in occupied habitat is 0.6 birds / ha, giving a total population size estimate of 8,280 birds, perhaps best rounded to c.8,000 individuals. This roughly equates to c.5,300 mature individuals. However, the population may be significantly smaller than this (D. Wiedenfeld in litt. 2012).

Population Trend
Decreasing
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Threats

Major Threats
Several threats are suspected to be causing population decline, including introduced species (diseases, parasites and predators), habitat degradation, and human disturbance (Vargas 1996, Wiedenfeld and Jiménez 2008, R. Curry in litt. 2005, H. Vargas in litt. 2005, A. Tye in litt. 2005, D. Wiedenfeld in litt. 2005). The presence of the Dipterid nestling parasite Philornis downsi is likely a significant threat (Wiedenfeld et al. 2007). A number of disease vectors have been introduced, including Culex quinquefasciatus (vector of avian malaria) and Simulium bipunctatus (Peck et al. 1998, Vargas and Bensted-Smith 2000, Whiteman et al. 2005), and chickens in the growing number of chicken farms have brought in new diseases and may act as intermediary hosts (Gottdenker et al. 2005). The incidence of parasites and diseases could be more important in the future with the increase in frequency and intensity of El Niño events and the more humid conditions in the islands (H. Vargas in litt. 2005, Wiedenfeld et al. 2007). Habitat loss and degradation is caused by invasive introduced plants (P. guajava, Eugenia jambos, Rubus niveus) (Vargas 1996), overgrazing by goats, and increased human settlement. Black rats and feral cats have been introduced and are thought to be responsible for high nest predation rates (Curry 1989). The relative importance and impacts of these different threats are not yet known.

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The global population of the San Cristobal mockingbird, restricted to a single island, is believed to be declining as a consequence of human activities (2) (6). The introduction of invasive plants and animals, and an increase in the size of the human population, has contributed to the loss and degradation of large areas of habitat on San Cristobal. Furthermore, feral rats and cats are thought likely to be responsible for high rates of predation on mockingbird nests, and there is a growing threat of avian parasites and diseases spreading to mockingbirds from local chicken farms (2).
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Management

Conservation Actions

Conservation Actions
Conservation Actions Underway
The Galápagos National Park was gazetted in 1959, and includes almost all the land area of the islands. In 1979, the islands were declared a World Heritage Site (Jackson 1985).

Conservation Actions Proposed
Monitor population to determine trends. Research relative importance of different threats in order to identify effective conservation actions. Research into methods of control or eradication of the parasite Philornis downsi (D. Wiedenfeld in litt. 2012). Avoid further introduction of alien species. Establish a captive breeding population for future reintroductions and population supplementation.

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Conservation

For their unique biological diversity and significance, the Galapagos Islands are designated both a National Park and a World Heritage Site (2). As a consequence, conservation of the islands' native fauna and flora is a high priority. Currently the San Cristobal mockingbird is monitored on an annual basis to assess the health and status of the population (6). This is to be supported in the future by further research to identify which factors are of greatest threat to the species so that appropriate conservation action can be taken (2).
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Wikipedia

San Cristobal mockingbird

The San Cristóbal mockingbird or Chatham mockingbird (Mimus melanotis) is a species of bird in the Mimidae family. It is endemic to San Cristóbal Island in the Galápagos Islands of Ecuador.

Its natural habitats are subtropical or tropical dry forests, subtropical or tropical mangrove forests, subtropical or tropical dry shrubland, and subtropical or tropical moist shrubland.

Behavior[edit]

Although this species does not have white wing patches, it does a "wing flash" movement similar to that done by Mimus mockingbirds that do have such patches. It runs a short distance, briefly opens its wings to two-thirds of full extension, then extends them fully to a position just above horizontal.[2]

See also[edit]

References[edit]

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