Montserrat Oriole (Icterus oberi)

Other local names: Various authors have reported that it has the local name of Tannia Bird. However, this is a mistake; in fact the Tannia Bird is the Forest Thrush Cichlerminia lherminieri whose far-carrying song was thought to indicate the correct time to harvest Tannia. Along with some other West Indian oriole species, it has been called Banana Bird for many years, but the name is not in common use now.

The Montserrat Oriole has a curious relationship with the people of its island home. It is the national bird, and a ubiquitous symbol, seen all over the island in arts, crafts and advertising. It is a source of pride and great interest. Yet most Montserratians confess to never having seen one in the wild. Having evolved as Montserrat’s only endemic bird species some two million years ago, it has shown a remarkable longevity. Its ability to withstand the various assaults of volcanic eruptions and hurricanes (not to mention the odd ice age) is undoubtedly one of the reasons for its popularity: it symbolises the resilience that the people of Montserrat have demonstrated in abundance in recent years.

• The volcanic eruption destroyed the Soufrière Hills population and most of the South Soufrière Hills population. The remaining sites – both Important Bird Areas – are approximately 1,100 ha in the Centre Hills, and a remnant patch of about 200 ha in the South Soufrière Hills. The global population is estimated at a few hundred pairs, with a small captive population in the UK.
• The Montserrat Oriole is strictly a forest species, unlike its sister species in Martinique and St Lucia and the Greater Antillean Oriole, all of which will occur outside true forest in areas that have plenty of trees, such as gardens, orchards and timber plantations. It is extremely rare in dry forest and below 150 m asl, and is found mainly in mesic and wet forest, reaching peak abundance at about 500 m asl; however it is found in elfin forest right at the summit of Katy Hill – the highest point in the Centre Hills at 750 m asl. There was apparently a good population in the cloud forests of the Soufrière Hills (up to 900 m asl) prior to the eruption. Within its mesic and wet forest habitat, the oriole does not appear to be a specialist on any particular habitat features.

Interesting Facts

• In common with other members of its genus, the Montserrat Oriole expertly weaves a basket nest which is suspended beneath a leaf of a broad leaved plant. More unusually, the Centre Hills population of orioles uses almost exclusively the leaves of Heliconia caribbaea as a nest plant. Appropriately enough, this is the national plant of Montserrat. This preference is a distinct oddity. It is unusual for a bird to be so specialised on one plant species, and the orioles take it even further, as they avoid both young and old leaves, selecting those that are of intermediate age. Yet those birds that do select the leaves of other plants seem to be just as successful in nesting. The use of Heliconia leaves is convenient for researchers, making nests rather easy to find, but perhaps an imperfect strategy for the birds. Heliconia leaves are vulnerable to falling over in droughts and under ashfall.
• A large colour-ringed population is now established in the Centre Hills, which has given many important insights into the ecology of the species. Initial attempts to colour-ring birds were stymied when it was discovered that they are very capable of removing plastic colour-rings, causing considerable confusion to the fieldworkers. Anodised coloured aluminium rings are now used. With their high rates of nest failure, multiple nesting is absolutely critical to oriole population biology, and colour-ringing allows researchers to follow pairs’ activities right through the breeding season.

Threats

• Montserrat Oriole is Critically Endangered, making it, with Semper’s Warbler, the most endangered breeding bird in the Lesser Antilles
• The eruption of the Soufrière Hills volcano from 1996 to present has destroyed about 60% of the former range of the oriole, including its main hotspots. Heavy and repeated ashfalls in the main surviving forest patch in the Centre Hills cause substantial, though temporary, reductions in the abundance of insect food, and bring down active nests. As we write, the volcano is as active now as at any time since 1996, and the prognosis for the future is uncertain. Nevertheless, to a large extent the volcano has now done its damage: the Centre Hills population and the remnant South Soufrière population can probably survive the current level of activity: only a truly catastrophic eruption could make things much worse.
• Having been reduced to a few hundred pairs in two small patches, however, the species is very vulnerable to other threats. Research in the Centre Hills in recent years shows that two factors are of particular concern. Firstly, there is a very high rate of nest predation by two opportunist predators – black rats and pearly-eyed thrashers Margarops fuscata. Both are extremely abundant in the area, and can destroy over three quarters of oriole nests in bad years. Secondly, seasonal rainfall seems to have an important effect on the oriole population. When the dry season is dry, breeding success is low. When the wet season is wet, adult survival is low. A run of dry season droughts would cause major problems. A looming threat is the feral pig population, which is spreading fast in Montserrat. In the long-run the pigs could severely damage the forest itself.

Conservation Measures

The Montserrat Oriole is in the fortunate position of being valued very highly by the people of Montserrat: in short, they will not let it disappear. Important steps to improved management of the Centre Hills are being made, with a Darwin Initiative project to create a Protected Area and a Management Plan. This will create the conditions for habitat protection and management that will benefit the species. Much information has already been gathered through the Oriole Emergency Conservation Programme, and the Montserrat Biodiversity Assessment, and more research is under way into the wider impacts of rats on the Centre Hills. A pig eradication programme is being developed. Despite the multitude of serious threats, and its Critically Endangered status, the prospects for the species are improving.

Where to Find More Information?  

Websites of partner organisations:

• Darwin Centre Hills Project
• Royal Society for the Protection of Birds (leading research on the species)
• Durrell Wildlife Conservation Trust (managing the captive population)
• BirdLife International (species profile and Red List information)

Scientific papers and reports:

Dalsgaard, B, Hilton, GM, Gray, GAL, Aymer, L, Boatswain, J, Daley, J, Fenton, C, Martin, J, Martin, L, Murrain, P, Arendt, WJ, Gibbons, DW & Olesen, JM (2007). Impacts of a volcanic eruption on the forest bird community of Montserrat, Lesser Antilles. Ibis. doi: 10.1111/j.1474-919x.2006.00631.x.

Hilton, G.M., P.W. Atkinson, G.A.L. Gray, W.J. Arendt, & D.W. Gibbons (2003). Rapid decline of the volcanically threatened Montserrat Oriole. Biological Conservation 111; 79-89.

Arendt, W. J., Gibbons, D. W., Gray, G. A. L., 1999. Status of the volcanically threatened Montserrat Oriole Icterus oberi and other forest birds in Montserrat, West Indies. Bird Conservation International 9, 351-372.

Hilton, GM, Gray, GAL, Fergus, E, Sanders, SM, Gibbons, DW, Bloxam, Q, Clubbe, C and Ivie, M (eds) (2005). Species Action Plan for the Montserrat Oriole Icterus oberi. Department of Agriculture, Montserrat. ISBN 1 90193071

Montserrat Oriole Bird of the Month contributed by Geoff Hilton

Bird of the Month - March 2007 - Grenada Dove

Bird of the Month - January 2007 - Bicknell's Thrush

Bird of the Month - December 2006 - Rose-throated Parrot

Bird of the Month - November 2006 - Purple-Throated Carib

Bird of the Month - October 2006 - Palmchat

Bird of the Month - September 2006 - Elfin-woods Warbler

Bird of the Month - August 2006 - Red-billed Streamertail

Bird of the Month - July 2006 - Cahow or Bermuda Petrel

Bird of the Month - June 2006 - West Indian Whistling-Duck

Range and Habitat Needs

• In recent decades, the species has been confined to hill forests in the Centre Hills, Soufrière Hills and South Soufrière Hills of Montserrat. Before the eruption of the Soufrière Hills volcano in 1996, the species probably had a range of about 30 km2 (the island of Montserrat is 109 km2). There are historical reports that it once also occurred in the Silver Hills in the north of the island, but this site is now heavily degraded dry forest and scrub, unsuitable for orioles.