Socorro mockingbird

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Socorro mockingbird

Critically Endangered  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Mimidae
Genus: Mimus
Species:
M. graysoni
Binomial name
Mimus graysoni
(Lawrence, 1871)
Synonyms

Mimodes graysoni Ridgway, 1882

The Socorro mockingbird (Mimus graysoni) is an

Andrew Jackson Grayson
.

Mimus graysoni shows its close relationship to the northern and tropical mockingbirds rather subtly. It is a much stouter bird, resembling some thrashers in habitus. It also has a distinct juvenile plumage, more rufous above and has a heavy pattern, especially below. This uncannily resembles, e.g., the gray thrasher (Toxostoma cinereum) from Baja California,[2] but is apparently a case of convergent evolution.[3]

Systematics and taxonomy

This is a rather distinct

sequences.[3]

Rather, the present species is closely related to the

ecological change from its ancestors; therefore its distinctiveness is not informative except supporting the theory that it is one of the older Socorro endemics.[2]

Thus, and because the adaptation to the peculiar conditions on Socorro may even have accelerated not only

taxa
are very close relatives.

Ecology and status

The Socorro mockingbird today lives mainly in unmodified low

humid forest in the uplands and were busy singing and defending territories.[2] Today, they mainly remain in Ficus cotinifolia stands when visiting the lower elevations.[1] The breeding season is extended, with nests in attendance between November and July, with the peak laying occurring in March and April.[1] Three eggs are laid, which take no more 15 days to hatch.[1]

The birds are generally reluctant to fly and as late as the mid-20th century were still fatally unwary; if pressed they will rather hop away than fly and if they take wing, it is usually for a few meters only.

predators, but red-tailed hawks and great frigatebirds
that not infrequently prey on mockingbird-sized birds.

This species feeds on small

social hierarchy between birds and rarely are more than two or three actively feeding; the less dominant birds hang around nearby, waiting for their turn.[2]

The call is two medium followed by one lower whistle. Less often, a full song is given, consisting of a variable warbling tune, repeated several times as in many

Socorro towhee and Socorro wren would seem to possess songs that might serve as models for the mockingbirds, and except the parula these are not often found in the mockingbird's core habitat.[2]

Status and conservation

This species numbers fewer than 400 individuals altogether and is considered

habitat loss caused by feral sheep and the locust Schistocerca piceifrons, and predation by feral cats which became established after 1953, probably in the early 1970s. It is not believed that the northern mockingbird which has colonized Socorro in the late 20th century is limiting the recovery of its relative; the two Mimus do not occupy the same habitat and even if they did, the native bird is larger and more powerful and would probably simply outcompete its mainland relative in native vegetation at least. The extermination of the sheep is underway in the hope of restoring the island ecosystem.[1]

On one hand, it seems that the Socorro mockingbird is a prolific species and would be able to increase in numbers quickly if habitat improves. On the other hand, its terrestrial habits make it vulnerable to cat predation and this may limit its recovery even if sheep are contained; it is not known for example in how far foraging in the lowlands – now cat-ridden – was important for robust breeding success. In addition, it can be expected that predation on this species by both the native red-tailed hawk as well as the feral cats has increased since the Socorro dove – formerly a preferred prey item – has become extinct in the wild. Cerro Evermann, Socorro's main volcano, is still active and erupts on a limited scale every few decades;[5] as the mockingbirds seem to depend on upland forest habitat, a major eruption could place the species in jeopardy (see also San Benedicto rock wren). This threat is not considered significant compared to the problem of introduced species however.[1]

Notes

  1. Engelmann's Prickly Pear
    (Opuntia engelmannii): Brattstrom & Howell (1956)

References

  1. ^
    doi:10.2305/IUCN.UK.2020-3.RLTS.T22711084A179825007.en
    . Retrieved 12 November 2021.
  2. ^
    JSTOR 1364977
    .
  3. ^
    doi:10.1111/j.0908-8857.2004.03233.x. Archived from the original
    (PDF) on 2008-09-07.
  4. S2CID 51797284
    .
  5. ^ Global Volcanism Program (2007): Socorro. Version of 2007-JUN-10.

External links

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