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Bateleur (Terathopius ecaudatus) Fact Sheet: Physical Characteristics

Terathopius ecaudatus, Bateleur

Physical Characteristics

Body measurements

Attribute Measurement
Head-body length 550-700 mm (21.7-27.6 in)
Tail length 100-120 mm (3.9-4.7 in)
Wing span 1680-1900 mm (66.1-74.8 in)
Hind claw 28.2-37.9 mm (1.1-1.5 in)
Inner claw 29.2-33.7 mm (1.1-1.3 in)
Body weight 1.8-3.0 kg (4.0-6.6 lb)

 

Measurements from Ferguson-Lees and Christie (2001); Smeenk (1974).

General Appearance

Body shape (from Ferguson-Lees and Christie 2001 unless otherwise noted)

  • A medium-sized snake-eagle
  • Tail
    • Very short (Moreau 1945)
    • Feathers completely concealed by the folded wings when perched (Johnston 1902)
    • Legs and feet stick out beyond the tail when in flight; adults only (Brown and Cade 1972; Smeenk 1974)
  • Wings
    • General shape
      • Long, bow-shaped
      • Pinched at bases
      • Broad across the secondaries
      • Tips relatively narrow, pointed, and upturned
    • Primary feathers
      • Long and pointed (from Moreau 1945)
    • Secondary feathers
      • Numerous; c. 25 secondary feathers
        • More than most other birds of prey
  • Legs
    • Bright red (Moreau 1945)

Facial characteristics (from Ferguson-Lees and Christie 2001 unless otherwise noted)

  • Head
    • Large cowl of feathers
  • Bill
    • Tricolored appearance, in adults
      • Tip black with yellow center
      • Bright red skin exposed at base of bill (Moreau 1945)
    • Juvenile bill primarily pale gray-blue
  • Eyes
    • Brown in all ages

Adult plumage

  • White, chestnut, gray, and black
  • Body color
    • Two color phases with varying colors on the back (from Moreau 1945 unless otherwise noted)
      • Back chestnut or creamy white
        • Chestnut coloration more common; c. 7% of adults with cream-colored backs (Kemp et al. 2013)
        • Cream color morph possibly more common in drier regions (Kemp et a. 2013)
  • Wings
    • Ventral view (from Kemp et al. 2013)
      • Mostly white from below
      • Black trailing edge
  • Dorsal view
    • Appearance of males and female dissimilar
      • Refer to descriptions of sexual dimorphism below

Juvenile plumage (from Brown and Cade 1972 unless otherwise noted)

  • Body
    • Light, straw brown
    • Gray-brown on the back
    • Feathers soft and dull in texture
  • Wings
    • More rounded than in adults
    • Entire wing dark from below
  • Tail
    • Longer than in adults
      • In flight, the tip projects beyond the feet
        • Extending c. 55 mm (c. 2.2 in) beyond the feet
    • Rounded
      • Becoming more squared-off with age
  • Facial skin and legs
    • Blue-green (Kemp et al. 2013)
    • Turning orange before assuming scarlet color of the adult (Kemp et al. 2013)
  • Molt
    • Timing of molts variable
    • First molt occurring after 1 year of age
    • Tail feathers becoming shorter with each consecutive molt

Sexual Dimorphism

Dimorphic in appearance (from Kemp et al. 2013 unless otherwise noted)

  • Wings of sexes dissimilar in adults
    • Sexes separable when perched or in flight
      • Sexes become easily apparent at c. 4-5 years of age (Brown and Cade 1972)
    • Dorsal view
      • Female with grayish-white secondary feathers
        • Wing appears banded, black feathers separate the grayish-white secondaries from similarly colored feathers at the shoulder
          • Primaries black
      • Male with mostly black secondary feathers
        • Grayish-white feathers confined to the shoulder area
    • Ventral view
      • Black band on the trailing edge of wing broader and more irregular in males when viewed from below (Brown 1955; Brown and Cade 1972)
  • Female c. 6% larger than male (Ferguson-Lees and Christie 2001)

Other Physical and Physiological Characteristics

Chromosome number

  • 33 pairs of chromosomes (2n=66) (Bed’Hom et al. 1998)

 Features of age and sex classes (from Brown and Cade 1972)

Age/sex classTail lengthTail shapeUnderwingBody color
Juvenile (>1 yr) Extends beyond feet Rounded Light brown Light brown
Immature (c. 1-3 yr) Extends to feet Rounded Light brown Light brown
Subadult (c. 4-5 yr) Extends to feet Slightly rounded Brown Dark brown
Pre-adult (c. 1-3 yr) Ends in advance of feet More square Mottled dark brown and white Dark brown; chestnut
Adult male (c. 1-3 yr) Ends in advance of feet Sharply square White with a broad, black trailing edge Black, white, and chestnut
Adult female (c. 1-3 yr) Ends in advance of feet Sharply square White with a narrow, black trailing edge Black, white, and chestnut

Color Changes With Age

Juvenile and adult bateleur

Plumages of a juvenile (left) and an adult (right) Bateleur.

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

Page Citations

Bed’Hom et al. (1998)
Brown (1955)
Brown and Cade (1972)
Ferguson-Lees and Christie (2001)
Johnston (1902)
Kemp et al. (2013)
Moreau (1945)
Smeenk (1974)

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