Icterus oberi (Montserrat Oriole)
Lawrence, 1880
Identification: 20–22 cm. Medium-sized, black-and-yellow icterid. Adult male, mostly black
with yellowish lower back, rump, shoulder, lower breast, belly and undertail. Female, dull
yellowish-green above and yellowish below. Immature duller. Voice Loud whistles and harsh
chuur.
Taxonomic source
AOU checklist (1998 + supplements)
Sibley and Monroe (1990, 1993)
Stotz et al. (1996)
Population trend details (Note: zeros may equate to 'unset')
Trend period: 1998 - 2008
Trend: decreasing
Data quality: medium
Data derivation: estimated (directly)
Fluctuation: unknown
Decline (10 years/3 generations past): 0 or Estimate: 50-79
Decline (10 years/3 generations future): 0 or Estimate: unknown
Decline (10 years/3 generations past+future): 0 or Estimate: unset
Trend justification: Variety of monitoring and analytical techniques indicate annual declines
of 8-52% during the period 1997-2000 (Hilton et al. 2003) following a rapid one-off
event when a volcanic eruption caused a 60% decrease in range and population in 1996.
However, recent trends suggest the 1997-2000 declines were merely a downward
fluctuation and the population is now recovering and may increase (Hilton in litt. 2007).
Range details (Note: zeros may equate to 'unset')
Year: 2000
EOO (br/res): 16
Year: 0
AOO (br/res): 0
Number of locations: 2
Locations band: unset
EOO (non-br): 0
AOO (non-br): 0
Fragmentation: severe
Data quality: good
Data quality: unset
Taxonomy:
Population and Range: Icterus oberi 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, Soufière and South Soufière hills), but volcanic activity
in 1995-1997 entirely destroyed two-thirds of remaining habitat4. Initially, only the Centre
Hills (c.14 km2) population was thought to have survived the pyroclastic flows (although even
this area was heavily ashed)1,2, 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 volcano7,8. In
December 1997, the estimated population was c.4,000 birds1, but intensive monitoring
between 1997-2001 indicated that the Centre Hills population declined by 40-50%, despite
reduced volcanic activity4,10. 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
breeding4,7,11. Recent evidence suggests that the downward fluctuation noted between 19972001 has reversed and the population is estimated at c.100-400 pairs and possibly
increasing4,10,12.
Country distribution
Montserrat (to UK)
Extinct
no
Occur status
N
Res.
yes
Br.
yes
Non-Br.
no
Passage
no
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 forest4,5. It is found in all
successional stages, and sometimes at the edges of cultivated areas and banana plantations4.
Nesting occurs in March-August, but the exact timing probably depends on the rainy
season2,5. Nests are mainly suspended from the leaves of Heliconia caribbaea, although
banana and other broad-leaved trees are also used4. Clutch size is typically two or three.
Unsuccessful pairs may attempt up to five clutches; successful pairs can rear two broods per
year4. It forages at all levels, but particularly in the understorey, feeding mainly on insects,
but occasionally also on fruit and possibly nectar4.
Altitude: 100 - 900 (Note: zeros may equate to 'unset')
Habitat
Forest
Type
Subtropical/tropical montane moist forest
Season
resident
Tolerance
medium
Importance
critical
Threats: Volcanic eruptions in 1995-1997 all but extirpated the species from the Soufière and
South Soufière hills. Although volcanic activity was reduced in 1998-2000, the population
continued to decline4,10. Potential causes are low insect availability and/or chronic ill-health of
birds resulting from ash fall on remaining forest, and other unknown and indirect knock-on
effects of volcanic activity4. 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 densities4,7,8. 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 areas4. Conversely, excessive rainfall
can also have a negative impact. There is no nest parasitism by Shiny Cowbird Molothrus
bonariensis, because this species does not currently occur on Montserrat2contra6.
Threat
changes in native species dynamics
Cause
predators
Timing
continuing
Scope
whole
Severity
very rapid
decline
very rapid
decline
very rapid
decline
Impact
high
invasive alien species (directly affecting the
species)
natural disasters
predators
continuing
whole
storms/flooding
whole
natural disasters
volcanoes
habitat loss/degradation (other)
natural disasters
unset
drought
suspended (may
return in short
term)
suspended (may
return in short
term)
continuing
continuing
whole
very rapid
decline
high
whole
whole
slow decline
fluctuations
medium
medium
high
high
Action: There is a comprehensive programme to monitor the population and breeding
success3,4, and in 2001 a new research programme into the causes of the continuing decline
was begun7. During 2003, preliminary tests of management interventions were made, aimed
at boosting reproductive success4. In June 1999, eight birds were taken to Jersey Zoo to
enable the development of husbandry techniques and initial attempts at captive breeding have
proven successful4,9. The Centre Hills has been designated a protected area and development
is not permitted within its marked boundaries2.
Targets: •Continue the existing programme and research into the causes of the decline.
•Develop potential management interventions to boost reproductive success4. •Continue the
close monitoring of the population4. •Investigate the reasons for the high densities of nest
predators in the Centre Hills4.
References: 1. Arendt et al. (1999). 2. P. Atkinson in litt. (1998, 1999). 3. Gibbons et al.
(1998). 4. G. Hilton in litt. (2000, 2003). 5. Jaramillo and Burke (1999). 6. Raffaele et al.
(1998). 7. Cotinga 17 (2002): 7. 8. Bowden et al. (2001). 9. Owen (2000). 10. Hilton et al.
(2003). 11. Anon (2006). 12. G. Hilton in litt. (2007).
Contributors
P Atkinson (unset)
Geoff Hilton (Royal Society for the Protection of Birds)
Red List evaluators
Jeremy Bird (BirdLife International)
Stuart Butchart (BirdLife International)