The slender-billed oriole (Oriolus tenuirostris) belongs to the family of figbirds and orioles, the Oriolidae.
The slender-billed oriole species is distributed in India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Vietnam and China. These oriole species were formerly considered conspecific with Oriolus chinensis. These orioles are polytypic species.
Appearance, physical description and identification
The slender-billed oriole (Oriolus tenuirostris) is a medium-sized oriole, measuring 20 to 25 cm in length and weighing 70 to 90 grams.The adult slender-billed oriole has bright golden-yellow head, upperparts and underparts. The wings have black patches. There is a broad blackish band from the lores, passing through the eyes to meet at the nape.
The uppertail is blackish with yellow edges. The undertail is golden yellow. The juveniles have dull yellow plumage. In juveniles, the eye band is diffuse and the underparts have dark streaks.
The bill is slender, long and pinkish. The irises are reddish. The legs and feet are gray. The call of these slender-billed oriole species is a loud fluty whistling "wheeow" sound.
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| Birds of India - Image of Slender-billed oriole - Oriolus tenuirostris by Peter Gronemann |
Origin, geographical range and distribution
These slender-billed oriole species are distributed in India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Vietnam and China. Vagrant birds have been observed in Sri Lanka.In India, these slender-billed oriole species are distributed in the states of northern West Bengal, Sikkim, Assam, Meghalaya, Arunachal Pradesh, Nagaland, Manipur, Tripura and Mizoram.
The slender-billed oriole nominate subspecies O. t. tenuirostris is distributed in Nepal, Bhutan, northeast India, Myanmar, Thailand, Laos, Vietnam and China. The subspecies O. t. invisus is distributed in southern Vietnam.
The Important Bird and Biodiversity Areas (IBA) of the slender-billed oriole species in Nepal are Dang Deukhuri foothill forests and west Rapti wetlands. The IBA in Laos is Phou Loeuy.
Ecosystem and habitat
These slender-billed oriole species have moderate forest dependence. They normally occur in altitudes from 0 to 2000 meters. The artificial ecosystems and habitats of these species include heavily degraded forests.The natural ecosystems and habitats of these slender-billed oriole species include tropical and subtropical moist lowland forests, evergreen forests, tropical and subtropical moist montane forests and dry deciduous forests.
Diet and feeding behavior
The diet of these slender-billed oriole species consists mainly of fruits. Wild fruits, berries and figs are their primary food. They are arboreal and known to feed on nectar from the flowers of the Salmalia sp. and Erythrina sp.Reproduction and breeding habits
The breeding season of these slender-billed oriole species is from April to June in much of their range. These oriole species are monogamous and territorial.The slender-billed oriole nesting sites include fork and branches of trees. The nest is a deep-cup built with grass stems, leaves, roots and plant fibers. The clutch contains two or three eggs. Both the parents incubate the eggs.
Migration and movement patterns
These slender-billed oriole species are partially migratory birds. The breeding populations in northeast Myanmar and the adjoining southern China (Yunnan) are migratory.They move to northeast India, Nepal, Bhutan, Bangladesh and southern Myanmar and northwest Thailand for wintering. Much of the oriole populations in Myanmar, Laos and Vietnam are resident.
Post breeding, the juveniles of the resident slender-billed orioles may disperse and establish in new locations within the range. Within their range they may make local movements for feeding and breeding.
Slender-billed oriole - Quick Facts
- Scientific name: Oriolus tenuirostris
- Species author: Blyth, 1846
- Synonyms/Protonym: Oriolus tenuirostris Blyth, 1846
- Family: Oriolidae › Passeriformes › Aves › Chordata › Animalia
- Vernacular names: English: Slender-billed oriole, Chinese: 细嘴黄鹂, French: Loriot à bec effilé, German: Dünnschnabelpirol, Spanish: Oropéndola picofina, Russian: Тонкоклювая иволга, Japanese: ミナミコウライウグイス
- Other names: Slender-billed Oriole
- Distribution: India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Vietnam, China
- Diet and feeding habits: fruits, berries, figs, nutmegs
- IUCN status listing: Least Concern (LC)
Conservation and survival
The global population size of the slender-billed oriole (Oriolus tenuirostris) has not been quantified. The overall population trend of the species is not known.In most of its range, this oriole species is reported as scarce to locally fairly common (Grimmett et al. 1998). The generation length is 3.7 years. Its distribution size is about 1,600,000 sq.km.
Habitat alteration, fragmentation and destruction, deforestation, human intrusions and disturbance and capture for pet-trade are the main threats that are endangering the survival of these oriole species.
IUCN and CITES status
The slender-billed oriole (Oriolus tenuirostris) does not approach the thresholds for being Vulnerable, either under the range size criterion, or under the population trend criterion or under the population size criterion.The IUCN (International Union for Conservation of Nature) has categorized and evaluated the oriole species and has listed it as of "Least Concern".
The CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) status is ‘Not Evaluated’ for the slender-billed oriole (Oriolus tenuirostris).
| Taxonomy and scientific classification of Oriolus tenuirostris | |
|---|---|
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Oriolidae |
| Subfamily: | - |
| Genus: | Oriolus |
| Species: | O. tenuirostris |
| Binomial name: | Oriolus tenuirostris |
| IUCN status listing: |
 Least Concern |
The two recognized subspecies of the slender-billed oriole (Oriolus tenuirostris) are:
O. t. tenuirostris Blyth, 1846 and
O. t. invisus Riley, 1940.
Image source: https://www.flickr.com/photos/39463459@N08/6935459331/ (cropped)
Image author: Peter Gronemann | License: CC BY 2.0 as on 5/11/18
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