Overview

Distribution

Range Description

This species inhabits an extremely small area on Montserrat (to UK) in the Lesser Antilles. By the early 1990s, it occurred throughout the three main forested hill ranges on the island (the Centre, Soufrire and South Soufrire hills), but volcanic activity in 1995-1997 entirely destroyed two-thirds of remaining habitat (G. Hilton in litt. 2000, 2003). Initially, only the Centre Hills (c. 14 km2) population was thought to have survived the pyroclastic flows (although even this area was heavily ashed) (P. Atkinson in litt. 1998, 1999, Arendt et al. 1999), but a remnant population was later discovered in a 1-2 km2 forest patch in the South Soufrire Hills, just one km from the summit of the volcano (Bowden et al. 2001). In December 1997, the estimated population was c. 4,000 birds (Arendt et al. 1999), but intensive monitoring between 1997-2003 indicated that the Centre Hills population declined by 40-50%, despite reduced volcanic activity (G. Hilton in litt. 2000, 2003, Hilton et al. 2003). In 2001, 2003 and 2006, further major volcanic eruptions caused heavy ash falls on large areas of the Centre Hills, destroying several nests and curtailing breeding (G. Hilton in litt. 2000, 2003,Anon.2006). The rapid declines noted between 1997-2003 may now have ceased, but population levels remain at less than 50% of those of 1997, with a total population estimated at just 307-690 birds (212-1,131, 95% CI) in 2012, c.80% in the Centre Hills and 20% in the South Soufrire Hills (Oppel et al. 2014a).
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Icterus oberi is endemic to the island of Montserrat and is the island's national bird. A small protectorate of the United Kingdom, Montserrat is only 102 km2 in area. These birds are commonly known as Montserrat orioles. A combination of catastrophic volcanic activity that started in 1995 and has continued to the present, and frequent hurricanes have decimated the birds’ population. The species is in danger of extinction.

Biogeographic Regions: neotropical (Native )

Other Geographic Terms: island endemic

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Range

Montane forests of Montserrat (Lesser Antilles).
  • Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2014. The eBird/Clements checklist of birds of the world: Version 6.9. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/

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Physical Description

Morphology

Montserrat orioles are the only sexually dimorphic, sedentary, tropical orioles. In males, the tail and wings are entirely black, as well as the breast. The belly, rump, and the lower back are yellowish-tawny. Females are yellowish olive from the face down the belly to the rump. Their wings are a darker olive brown, and their tails are olive. Immature males closely resemble mature females, yet they have darker backs, and may have a few black throat feathers. Juveniles also resemble mature females, but they have a yellow wash about their rumps, underparts, and crowns, greenish-yellow faces, and olive flanks.

Range wingspan: 88 to 98.5 mm.

Average wingspan: 92.6 mm.

Other Physical Features: endothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful

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Type Information

Cotype for Icterus oberi Lawrence
Catalog Number: USNM 81067
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Male; Immature
Preparation: Skin: Whole
Collector(s): F. Ober
Locality: Montserrat, North America
  • Cotype: Lawrence. December 30, 1880. Proc. U.S. Nat. Mus. 3: 351.
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Cotype for Icterus oberi Lawrence
Catalog Number: USNM 81068
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Female; Adult
Preparation: Skin: Whole
Collector(s): F. Ober
Locality: Montserrat, North America
  • Cotype: Lawrence. December 30, 1880. Proc. U.S. Nat. Mus. 3: 351.
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Cotype for Icterus oberi Lawrence
Catalog Number: USNM 81066
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Male; Adult
Preparation: Skin: Whole
Collector(s): F. Ober
Locality: Montserrat, North America
  • Cotype: Lawrence. December 30, 1880. Proc. U.S. Nat. Mus. 3: 351.
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© Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds

Source: National Museum of Natural History Collections

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Cotype for Icterus oberi Lawrence
Catalog Number: USNM 81066
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Male; Adult
Preparation: Skin: Whole
Collector(s): F. Ober
Locality: Montserrat, North America
  • Cotype: Lawrence. December 30, 1880. Proc. U.S. Nat. Mus. 3: 351.
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© Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds

Source: National Museum of Natural History Collections

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Cotype for Icterus oberi Lawrence
Catalog Number: USNM 81067
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Male; Immature
Preparation: Skin: Whole
Collector(s): F. Ober
Locality: Montserrat, North America
  • Cotype: Lawrence. December 30, 1880. Proc. U.S. Nat. Mus. 3: 351.
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© Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds

Source: National Museum of Natural History Collections

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Cotype for Icterus oberi Lawrence
Catalog Number: USNM 81068
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Female; Adult
Preparation: Skin: Whole
Collector(s): F. Ober
Locality: Montserrat, North America
  • Cotype: Lawrence. December 30, 1880. Proc. U.S. Nat. Mus. 3: 351.
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© Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds

Source: National Museum of Natural History Collections

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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
It occurs in most forest types between c. 150-900 m, but reaches highest densities in wetter, higher altitude forests, and is absent from areas of very dry forest (Jaramillo and Burke 1999, G. Hilton in litt. 2000, 2003). It is found in all successional stages, and sometimes at the edges of cultivated areas and banana plantations but appears to be an obligate forest species (G. Hilton in litt. 2000, 2003). Nesting occurs in March-August, but the exact timing probably depends on the rainy season (P. Atkinson in litt. 1998, 1999, Jaramillo and Burke 1999). Pre-breeding season rainfall increases food availability which leads to improved body condition of females and increased fecundity (Oppel et al. 2013). Nests are mainly suspended from the leaves of Heliconia caribbaea, although banana and other broad-leaved trees are also used (G. Hilton in litt. 2000, 2003). Its clutch-size is typically two or three. Unsuccessful pairs may attempt up to five clutches; successful pairs can very rarely rear three broods per year (G. Hilton in litt. 2000, 2003). It forages at all levels, but particularly in the understorey, feeding mainly on insects, but occasionally also on fruit and possibly nectar (G. Hilton in litt. 2000, 2003).

Systems
  • Terrestrial
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Montserrat orioles are found in the humid mountain forests of their small eastern Caribbean island home. These unique birds seem to prefer areas of dense vegetation, at high altitudes, where the air is cooler.

Range elevation: 230 to 800 m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest ; mountains

  • Raffaele, H., J. Wiley, O. Garrido, A. Keith, J. Raffaele. 1998. A Guide to the Birds of the West Indies. Princeton, New Jersey: Princeton University Press.
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Trophic Strategy

Montserrat orioles are thought to be almost entirely insectivorous in the wild, foraging for insects on the undersides of leaves. Frugivorous feeding has not been well documented in the wild, but a captive population at the Jersey Zoo is fed papaya and mango. Montserrat orioles have not been observed eating nectar.

Animal Foods: insects; terrestrial non-insect arthropods

Plant Foods: fruit

Primary Diet: carnivore (Insectivore )

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Associations

As the ecosystem of Montserrat has been perturbed so much through human deforestation and volcanic activity, and because there are so few Montserrat orioles left, it is hard to evaluate their ecosystem roles. However, as they do prey on insects, they may have a role in controlling insect populations. Volcanic ash-falls have negatively impacted insect populations, and subsequently decreased the amount of food available to Montserrat orioles. The degree to which they eat fruit in the wild is not well understood, but it is unlikely that they are instrumental in seed dispersal or pollination. Populations of introduced rats frequently prey on the nests of I. oberi, resulting in a high percentage of nest failure.

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Researchers from the Royal Society for the Protection of Birds studied predation of Montserrat oriole nests through the use of infrared micro-cameras. Very high rates of predation by rats were observed; it was thought that most nesting failures were a result of rat predation.

Known Predators:

  • house rats (Rattus rattus)
  • Norway rats (Rattus norvegicus)

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Life History and Behavior

Behavior

Montserrat orioles call only in the breeding season, during which they call infrequently. The call is composed of single notes, sung at intervals of 2.5 to 3 seconds, comparable to the tempo red-eyed vireo vocalizations. The notes are generally only one or two short syllables or low gurgles. Siegel (1983) described the call as a sharp "chic" or sharper "chuck," while Raffaele et al. (1998) describe as a "series of loud whistles and a harsh, scolding chuur call."

Communication Channels: visual ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

  • Siegel, A. 1983. The Birds of Montserrat. Montserrat, West Indies: Montserrat National Trust.
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Life Expectancy

There is no published data available on the lifespan of Montserrat orioles. However, with a captive breeding program underway at the Jersey Zoo, lifespan data may be forthcoming.

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Reproduction

Montserrat orioles breed seasonally. Males sing, however infrequently, to attract females. Females build hanging nests from vegetative matter, without the help of males. Montserrat orioles are monogamous.

Mating System: monogamous ; cooperative breeder

Montserrat orioles nest yearly, from June to August. Their long, hanging nests are built from vegetation. Like many other species in the genus Icterus, nests are pendulous baskets.

Breeding interval: Montserrat orioles breed once yearly.

Breeding season: Breeding occurs from June to August.

Range eggs per season: 2 to 4.

Range time to hatching: 12 to 14 days.

Range fledging age: 13 to 14 days.

Average fledging age: 13 days.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

Eggs are incubated only by the female, yet both parents feed and care for their young. Females incubate the eggs for about two weeks until the young hatch. The young remain in the nest for another two weeks, until they fledge. Parents can be observed with their fledgling young, continuing to feed them for varying lengths of time.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

  • 2001. "Montserrat Oriole" (On-line). Jersey Zoo. Accessed November 08, 2006 at http://www.jerseyzoo.co.uk/.
  • Jaramillo, A., P. Burke. 1999. New World Blackbirds: The Icterids. Princeton, New Jersey: Princeton University Press.
  • Raffaele, H., J. Wiley, O. Garrido, A. Keith, J. Raffaele. 1998. A Guide to the Birds of the West Indies. Princeton, New Jersey: Princeton University Press.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Icterus oberi

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
CR
Critically Endangered

Red List Criteria
B1ab(i,ii,iii,iv)

Version
3.1

Year Assessed
2015

Assessor/s
BirdLife International

Reviewer/s
Symes, A.

Contributor/s
Atkinson, P. & Hilton, G.

Justification
This species has always had an extremely small range, but recent volcanic eruptions have caused an extremely rapid population decline and extirpated it from all but two disjunct areas. Deposits of volcanic ash have seriously damaged the habitat of the remaining population, and further deposits or an increased frequency of hurricanes could have devastating effects. Although the trend may have since stabilised, the future of this species in the wild remains uncertain, and it consequently qualifies as Critically Endangered. Confirmation of population size and trend may lead to its downlisting in future.


History
  • 2013
    Critically Endangered (CR)
  • 2012
    Critically Endangered (CR)
  • Critically Endangered (CR)
  • Critically Endangered (CR)
  • Critically Endangered (CR)
  • Critically Endangered (CR)
  • Critically Endangered (CR)
  • Lower Risk/near threatened (LR/nt)
  • Threatened (T)