Dollarbird (Eurystomus orientalis) – A Comprehensive Study

Taxonomy & Classification

• Scientific Name: Eurystomus orientalis
• Common Name: Dollarbird
• Family: Coraciidae (Roller family)
• Order: Coraciiformes
• Genus: Eurystomus
• Species: orientalis

The Dollarbird is a unique member of the roller family, distinct from the Indian Roller (Coracias benghalensis) due to its darker plumage and striking white wing patches. It gets its name from the silvery-white spots on its wings, which resemble silver “dollars” and become highly visible during flight.

 

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Morphological Features

Size & Dimensions

• Length: 27–30 cm (10.5–12 inches)
• Wingspan: 65–75 cm
• Weight: 130–160 grams

Coloration & Plumage

• Head & Neck: Deep bluish-green, giving a dark appearance in poor light.
• Upperparts: Dark greenish-blue with a glossy sheen.
• Underparts: Bluish-green to teal, slightly paler on the belly.
• Wings: Dark with conspicuous pale blue-white circular patches (the “dollars”).
• Tail: Short, broad, and dark blue with a slightly lighter tip.
• Eyes: Bright reddish-orange, adding a piercing look.
• Beak: Short, stout, and bright orange-red.
• Legs & Feet: Reddish-orange, well adapted for gripping perches.

Distinctive Features

• “Dollar” wing patches that shine in flight, making the bird easy to identify.
• Short, thick, and powerful beak, suited for catching insects in midair.
• Unlike other rollers, it prefers high perches rather than ground-based hunting.
• Flies in short bursts, often returning to the same perch.

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Habitat & Distribution

General Habitat

The Dollarbird is found in tropical and subtropical regions, preferring:

• Dense woodlands and forest edges
• Mangrove forests and coastal regions
• Riverbanks and floodplain forests
• Hilly regions with tall trees
• Open forests with scattered trees

Global Distribution

This species has a wide range across Asia and Australia, including:

• Indian Subcontinent: India (Northeastern states, Sundarban region, Andaman & Nicobar Islands), Bangladesh, Sri Lanka.
• Southeast Asia: Myanmar, Thailand, Malaysia, Indonesia, Philippines, Vietnam, Cambodia, Laos.
• East Asia: Southern China, Taiwan, Japan (migratory populations).
• Australasia: Papua New Guinea, Northern Australia.

Presence in Sundarban

The Sundarban mangrove ecosystem provides a suitable, though not very common, habitat for the Dollarbird.

• Found in tall mangrove trees along riverbanks and estuarine edges.
• Prefers open patches near water bodies, where it can catch insects in flight.
• Unlike the Indian Roller, it is more arboreal, staying high in tree canopies.
• Seasonal presence, with populations increasing during September to March due to winter migrations.

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Diet & Feeding Behavior

The Dollarbird is a carnivorous bird, specializing in aerial insect hunting. Its diet includes:

• Flying insects (beetles, moths, grasshoppers)
• Dragonflies and damselflies
• Termites and flying ants (especially during swarming seasons)
• Small reptiles (occasionally hunts lizards or skinks)
• Small birds and nestlings (rare, but sometimes observed)

Hunting Techniques

• Hunts from high perches, swooping down to snatch flying insects.
• Uses strong, hooked beak to crush hard-bodied insects.
• Performs aerial acrobatics, twisting and turning mid-air to chase prey.
• Unlike bee-eaters, it does not hover; instead, it returns to its perch after catching prey.

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Breeding & Nesting

• Breeding Season: April to August, peaking before monsoons.
• Nesting Sites: Prefers tree cavities, especially old woodpecker holes.
• Nesting Style: Uses natural hollows rather than excavating new ones.
• Eggs: Typically 3–4 white eggs per clutch.
• Incubation Period: Around 18–22 days.
• Parental Care: Both parents incubate eggs and feed chicks, ensuring high survival rates.

Nesting in Sundarban

• Found in tall, mature mangrove trees, often selecting hollow trunks.
• Nests are protected from tidal disturbances, unlike birds nesting in low areas.
• Due to limited large trees in dense mangrove zones, breeding is more common in buffer areas.

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Vocalization & Communication

• Call: A harsh, croaking “kak-kak-kak” or “rak-rak” sound, often repeated.
• Purpose: Used for territorial calls, alarm signals, and mate attraction.
• Calls are more frequent at dawn and dusk, when hunting activity is highest.

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Conservation Status & Threats

IUCN Status: Least Concern (LC)

The Dollarbird has a stable global population, but it faces localized threats:

• Habitat destruction due to deforestation and urbanization.
• Loss of nesting sites, as old tree cavities are removed for logging.
• Decline in insect populations due to pesticide use.
• Disturbance from tourism and human activity in breeding areas.

Conservation Efforts in Sundarban

• Sundarban Biosphere Reserve and National Park provide protected areas for breeding.
• Forest conservation programs help preserve large trees needed for nesting.
• Eco-tourism awareness ensures minimal human interference in nesting sites.

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Ecological Role in Sundarban

• Controls flying insect populations, preventing outbreaks of harmful species.
• Acts as an indicator species, reflecting the health of forested wetland ecosystems.
• Provides prey for larger raptors, such as hawks and falcons.
• Competes with other cavity-nesting birds like barbets and woodpeckers, helping regulate species balance.

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Conclusion

The Dollarbird (Eurystomus orientalis) is a striking, agile, and ecologically significant bird found in Sundarban and across tropical Asia. Its distinctive wing markings, aerial hunting skills, and preference for high perches set it apart from other rollers. Though not as common as the Indian Roller, it plays a vital role in maintaining insect population control and biodiversity balance.

With Sundarban’s conservation efforts, habitat preservation, and eco-tourism guidelines, the Dollarbird will continue to thrive, adding to the rich avian diversity of one of the world’s most unique ecosystems.