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Radjah Shelduck (Rajah rajah) Fact Sheet: Summary

Radjah Shelduck (Radjah radjah) Fact Sheet

Two Radjah Shelducks standing in ankle deep water

Radjah Shelduck (Radjah radjah)

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Taxonomy Physical Characteristics

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Anseriformes — ducks, geese, swans, screamers, waterfowl

Family: Anatidae — ducks, geese, swans

Genus: Radjah

Species: Radjah radjah — Radjah Shelduck

Subspecies: R. r. radjah — Moluccas Islands, New Guinea, Indonesia, and nearby islands
Subspecies: R. r. rufitergum — northern and eastern tropical Australia

590-1130 g (1.3-2.49 lb)

Head-body Length
485-610 mm (19.0-24 in)

Wing Length
246-298 mm (9.68-11.7 in)

Wing Span
900-1000 mm (30-40 in)

Head, neck, and underbody white; sometimes rust-stained. Breast band narrow and reddish-brown. Upperwing dark (reddish-brown in R. r. rufitergum; more black in R. r. radjah). Wing patch iridescent green. Sexes similar.

Distribution & Status Behavior & Ecology

Northern and north-eastern Australia, New Guinea, Indonesia, and adjacent islands

Many coastal habitats. Marshes, mangroves, tidal mudflats. Freshwater lagoons only used during dry season. Common near shallow water of river margins, creeks, floodplains, and lagoons.

IUCN Status
Least Concern (2016 assessment)

CITES Appendix
Not listed

Other Designations
Protected in Australia

Populations in the Wild
R. r. radjah: about 10,000-100,000 individuals
R. r. rufitergum: tentatively estimated at 150,000 individuals

Runs quickly. Slow but agile flier. Swims well but infrequently.

Activity Cycle
Roost during the day (nonbreeding season). Leave roost in late afternoon or at dusk. Feed in the early morning, evening, and at night.

Social Groups
Typically found in pairs or small family groups. Strong pair bonds. May gather in flocks of 20-60 individuals (maximum flock size not known).

Limited study. Appears to vary with geography. Molluscs, worms, insects, algae, and possibly seeds.

Reports of crocodiles and dingoes.
Not reported, but also very likely: foxes and feral cats.

Reproduction & Development Species Highlights

Sexual Maturity
Likely similar to other shelducks—about 2 years of age. Needs confirmation.

Breeding Season
Dependent on seasonal rainfall. Typically, February to July. Coincides with end of wet season/early dry season, when more food available.

Mating System
Thought to be monogamous. Probably form life-long pair bonds.

Clutch Size
About 9 eggs, on average. Precise range unclear; likely 5-12 eggs.

Incubation Period
About 30 days

Typical Life Expectancy
Not reported

Feature Facts

  • Large duck with a distinctive white head, narrow chestnut breast band, and a pale cream iris
  • Scientific name Radjah radjah comes from Hindi, meaning “king” or “ruler”
  • Rarely on water; prefers wading and shallow edges of marshes
  • Maneuverable flier—flies low through trees rather than over canopy
  • Runs swiftly
  • Usually found in pairs or small family groups
  • Often described as “pugnacious”
  • Very vocal, especially when roosting
  • Feeds almost entirely on land and in very shallow water (about 1-2 inches deep)
  • Breeding pair aggressively defends a breeding territory

About This Fact Sheet

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© 2019 San Diego Zoo Wildlife Alliance


How to cite: Radjah Shelduck (Radjah radjah) Fact Sheet. c2019. San Diego (CA): San Diego Zoo Wildlife Alliance; [accessed YYYY Mmm dd]. radjah-shelduck.
(note: replace YYYY Mmm dd with date accessed, e.g., 2018 Dec 31)


Disclaimer: Although San Diego Zoo Wildlife Alliance makes every attempt to provide accurate information, some of the facts provided may become outdated or replaced by new research findings. Questions and comments may be addressed to


Many thanks to Dr. John McEvoy for providing expert content review of this fact sheet.

Dr. McEvoy, postdoctoral fellow at the Smithsonian Conservation Biology Institute’s Conservation Ecology Center, conducts research on the behavioral ecology of animals. In particular, his work focuses on using knowledge of animal movements to inform the conservation of wide-ranging and nomadic species.

His Ph.D. research at Deakin University (Australia) investigated the spatial ecology of nomadic waterfowl in inland Australia. Some of Dr. McEvoy’s recent postdoctoral work includes the monitoring of water bird populations at continental scales and using new conservation technologies to improve approaches to counting waterfowl.

In addition to studying water birds, Dr. McEvoy also collaborates with many research groups and NGOs around the world on taxa as diverse as parrots, foxes, waterfowl, fish and elephants.

To learn more about Dr. McEvoy, view his research website and SCBI profile.

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