Overview

Distribution

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 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, Soufrière and South Soufrière 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 Soufrière Hills, just 1 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 Soufrière Hills (Oppel et al. 2013).
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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 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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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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Ecology

Habitat

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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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). 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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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:

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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

Since 2000, I. oberi has been listed by the IUCN as a critically endangered species. The IUCN outlines several reasons for decline of Montserrat orioles, including habitat destruction due to agriculture, invasive alien predators, drought, flooding, and the island's infamous volcanic eruptions.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: critically endangered

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IUCN Red List Assessment


Red List Category
CR
Critically Endangered

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

Version
3.1

Year Assessed
2013

Assessor/s
BirdLife International

Reviewer/s
Butchart, S.

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
  • 2012
    Critically Endangered
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Population

Population
In 2012 the total population was estimated at 307-690 birds (212-1,131, 95% CI), depending on whether the sampling area around each point count was assumed to encompass 100 m or 150 m (Oppel et al. 2013). The upper estimate comprises 546 (382–897) individuals in the Centre Hills, and 143 (94–234) individuals in the South Soufriere Hills (using a 100 m radius around points); and the lower is based on estimates of 243 (170–399) individuals in the Centre Hills, and 64 (42–104) individuals in the South Soufriere Hills (using a 150 m radius around points; Oppel et al. 2013). This very roughly equates to 200-460 mature individuals. Previous population estimates were of 460-590 pairs (260-1,190, 95% CI) or 920-1,180 mature individuals, and 5,200 individuals (based on 2004 survey data; Hilton 2008).

Population Trend
Stable
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Threats

Major Threats
Volcanic eruptions in 1995-1997 all but extirpated the species from the Soufrière and South Soufrière hills. Although volcanic activity was reduced in 1998-2000, the population continued to decline (G. Hilton in litt. 2000, 2003, Hilton et al. 2003). Potential causes are low insect availability (Marske et al. 2007) and/or chronic ill-health of birds resulting from ash fall on remaining forest, and other unknown and indirect knock-on effects of volcanic activity (G. Hilton in litt. 2000, 2003). Research into reproductive success, using nest cameras, has also revealed high rates of nest predation by rats and native Pearly-eyed Thrashers Margarops fuscatus, both of which occur at high but fluctuating densities (G. Hilton in litt. 2000, 2003, Bowden et al. 2001). Studies between 1998-2005 found nest success of 29% (n = 275 nests), and 87% of nest failures were due to predation by either introduced rats or Pearly-eyed Thrashers (Allcorn et al. 2012). In 2001 and 2003, drought appeared to cause reduced laying frequency and clutch-size, and this may be an increasing problem now that that species is confined to lower, drier areas (G. Hilton in litt. 2000, 2003). Conversely, excessive rainfall can also have a negative impact. A feral pig population is spreading fast and could cause serious damage to the forest habitat if not eradicated. Despite being previously proposed as a threat, there is no nest parasitism by Shiny Cowbird because this species does not currently occur on Montserrat (P. Atkinson in litt. 1998, 1999), contra Raffaele et al. (1998). Having a montane distribution that is close to the maximum altitude within its range, this species is also potentially susceptible to climate change (BirdLife International unpublished data).


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Management

Conservation Actions

Conservation Actions

Conservation Actions Underway
There is a comprehensive programme to monitor the population and breeding success (Gibbons et al. 1998, G. Hilton in litt. 2000, 2003), and in 2001 a new research programme into the causes of the continuing decline was begun (Cotinga 17 2002: 7). During 2003, preliminary tests of management interventions were made, aimed at boosting reproductive success (G. Hilton in litt. 2000, 2003). In June 1999, eight birds were taken to Jersey Zoo to enable the development of husbandry techniques; initial attempts at captive breeding proved successful (G. Hilton in litt. 2000, 2003, Owen 2000) and captive birds are now also present at several other locations in the UK, but there are currently no plans to augment the wild population with birds from captive stock (G. Hilton in litt. 2007, 2008). The Centre Hills has been designated a protected area and development is not permitted within its marked boundaries (P. Atkinson in litt. 1998, 1999). A Species Action Plan was published in 2005. Experimental rat control in the Centre Hills commenced in 2006 and work to compare nest success in an area with experimental rat control with nest success in adjacent areas with high rat density was scheduled for 2008 (G. Hilton in litt. 2007, 2008). A pig eradication programme is also planned for the island.

Conservation Actions Proposed
Continue the existing programme and research into the causes of the decline. Develop potential management interventions to boost reproductive success (G. Hilton in litt. 2000, 2003). Continue the close monitoring of the population (G. Hilton in litt. 2000, 2003, Oppel et al. 2013) and development of breeding programmes. Investigate the reasons for the high densities of nest predators in the Centre Hills (G. Hilton in litt. 2000, 2003), and focus on enhancing nesting success via rat control (Allcorn et al. 2012).
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Relevance to Humans and Ecosystems

Benefits

Negative economic impacts on humans are highly unlikely, due to their small population numbers.

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These birds provide a novel opportunity for the study of the evolution of sexual dimorphism. While their rareness makes them an exotic species for observation, most of their habitat is within restricted zones on Montserrat, making casual birding quite difficult.

Positive Impacts: ecotourism ; research and education

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Wikipedia

Montserrat oriole

The Montserrat oriole (Icterus oberi) is a medium-sized black-and-yellow icterid (the same family as many blackbirds, meadowlarks, cowbirds, grackles, and others, including the New World orioles).

It inhabits the Centre Hills and South Soufriere Hills Important Bird Areas on the island of Montserrat in the Lesser Antilles of the West Indies, and is the national bird of this British territory. It is threatened by habitat loss, and has been classified by BirdLife International as Critically Endangered, with a current estimated population of between 200 and 800. Much of its habitat was destroyed by deforestation, Hurricane Hugo and the volcanic activity between 1995 and 1997.

Female at Frankfurt Zoo, Germany

The oriole once was found in three main areas: the bamboo forest east of Galways Soufrière, the leeward slopes of the Chances Peak mountain and the Centre Hills (especially the Runaway Ghaut area).

The diet of the bird consists mainly of insects and fruits. The birds usually lay two spotted eggs. All models indicate that they begin breeding at one year old. Most of them were almost wiped out during the volcano eruptions and only about 200 of them are still surviving.

The binomial name of this bird commemorates the American naturalist Frederick Albion Ober.

References[edit]

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