Pearly-eyed Thrasher
Encyclopedia
The Pearly-eyed Thrasher (Margarops fuscatus) is a bird found in Puerto Rico
and the Virgin Islands
, the Bahamas and Antilles
. Its genus
, Margarops, is considered monotypic
today; formerly the Scaly-breasted Thrasher
was placed here too. The present species, however, is now known to be closer to the Cinclocerthia tremblers (Hunt et al. 2001, Barber et al. 2004).
It prefers to live in bushes and trees in mountain forests and coffee plantations. The Pearly-eyed Thrasher is described as an aggressive, opportunistic omnivore that feeds primarily on large insects, but also feeds on fruits and berries, and will occasionally eat lizards, frogs, small crabs and other bird’s eggs and nestlings. It grows to 28 to 30 cm (11 to 11.8 inches) in length.
This species nests in cavities. In Puerto Rico
, it is known to compete with the critically endangered Puerto Rican Amazon for nesting sites and may even destroy the eggs of this species.
While this is not a migratory
bird, considerable gene flow
between populations appears to have taken place at least until fairly recently in its evolution
ary history. Still, two subspecies
can be identified: Margarops fuscatus fuscatus which is found between the Greater Antilles
and Antigua and Barbuda
, M. f. densirostris, occurring from Montserrat
and Guadeloupe
southwards. When exactly the Pearly-eyed Thrasher lineage diverged from its relatives cannot be said with reasonable certainty at the moment, as no fossil
s are known and the standard molecular clock
model cannot be applied to the Mimidae as mutation
rates seem to have varied over time.(Hunt et al. 2003)
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Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
and the Virgin Islands
Virgin Islands
The Virgin Islands are the western island group of the Leeward Islands, which are the northern part of the Lesser Antilles, which form the border between the Caribbean Sea and the Atlantic Ocean...
, the Bahamas and Antilles
Antilles
The Antilles islands form the greater part of the West Indies in the Caribbean Sea. The Antilles are divided into two major groups: the "Greater Antilles" to the north and west, including the larger islands of Cuba, Jamaica, Hispaniola , and Puerto Rico; and the smaller "Lesser Antilles" on the...
. Its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, Margarops, is considered monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
today; formerly the Scaly-breasted Thrasher
Scaly-breasted Thrasher
The Scaly-breasted Thrasher is a species of bird in the Mimidae family found in the Caribbean Lesser Antilles. It was formerly united with the Pearly-eyed Thrasher in Margarops but now is again placed in the monotypic genus Allenia.It is found in Antigua and Barbuda, Barbados, Dominica, Grenada,...
was placed here too. The present species, however, is now known to be closer to the Cinclocerthia tremblers (Hunt et al. 2001, Barber et al. 2004).
It prefers to live in bushes and trees in mountain forests and coffee plantations. The Pearly-eyed Thrasher is described as an aggressive, opportunistic omnivore that feeds primarily on large insects, but also feeds on fruits and berries, and will occasionally eat lizards, frogs, small crabs and other bird’s eggs and nestlings. It grows to 28 to 30 cm (11 to 11.8 inches) in length.
This species nests in cavities. In Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
, it is known to compete with the critically endangered Puerto Rican Amazon for nesting sites and may even destroy the eggs of this species.
While this is not a migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
bird, considerable gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
between populations appears to have taken place at least until fairly recently in its evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary history. Still, two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
can be identified: Margarops fuscatus fuscatus which is found between the Greater Antilles
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
and Antigua and Barbuda
Antigua and Barbuda
Antigua and Barbuda is a twin-island nation lying between the Caribbean Sea and the Atlantic Ocean. It consists of two major inhabited islands, Antigua and Barbuda, and a number of smaller islands...
, M. f. densirostris, occurring from Montserrat
Montserrat
Montserrat is a British overseas territory located in the Leeward Islands, part of the chain of islands called the Lesser Antilles in the West Indies. This island measures approximately long and wide, giving of coastline...
and Guadeloupe
Guadeloupe
Guadeloupe is an archipelago located in the Leeward Islands, in the Lesser Antilles, with a land area of 1,628 square kilometres and a population of 400,000. It is the first overseas region of France, consisting of a single overseas department. As with the other overseas departments, Guadeloupe...
southwards. When exactly the Pearly-eyed Thrasher lineage diverged from its relatives cannot be said with reasonable certainty at the moment, as no fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s are known and the standard molecular clock
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...
model cannot be applied to the Mimidae as mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
rates seem to have varied over time.(Hunt et al. 2003)
Books
- Raffaele, H. A., 1989. A Guide to the Birds of Puerto Rico and the Virgin Islands (revised) , Princeton University Press, Princeton, NJ. p. 31, 151.
- Oberle, M. W., 2000. Puerto Rico’s Birds in Photographs (second edition) , Editorial Humanitas, San Juan, PR. p. 104-105.
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External links
- El Yunque National Forest: Wildlife Facts - January 2005 - Pearly-eyed Thrasher
See also
- Fauna of Puerto RicoFauna of Puerto RicoThe fauna of Puerto Rico is similar to other island archipelago faunas, with high endemism, and low, skewed taxonomic diversity. Bats are the only extant native terrestrial mammals in Puerto Rico. All other terrestrial mammals in the area were introduced by humans, and include species such as cats,...
- List of endemic fauna of Puerto Rico
- List of Puerto Rican birds
- List of Vieques birds