SPECIES

Saddle-billed Stork Ephippiorhynchus senegalensis Scientific name definitions

Jonah Gula
Version: 2.0 — Published June 25, 2021

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Identification

The characteristic black and white contrasting plumage and tricolored bill of adults make this species easily distinguishable from other storks or sympatric large waterbirds. In flight, the large size and the black wing bands are diagnostic . The plumage of both sexes is similar, but females are shorter, weigh less, and have yellow irises while those of males are brown (1, 2).

Similar Species

Adults are unmistakable among the African storks in flight and on the ground due to their size and striking coloration. In flight, the smaller Yellow-billed Stork (Mycteria ibis) has entirely black flight feathers and white upper and underwing coverts while the Saddle-billed Stork has white flight feathers and black upper and underwing coverts. Immatures are much larger than Abdim's Stork (Ciconia abdimii) and 'African' Woolly-necked Stork (Ciconia episcopus miscroscelis), which do not have white on the underwing as immature Saddle-billed Storks do from a young age. Whereas immature Saddle-billed Storks have gray heads and necks, adults of the Woolly-necked Stork have a dark contrasting forehead with a white neck and adult Abdim's Storks have a fully black head and neck and blue and red face. First-year Saddle-billed Storks do, however, show similarity to immature Yellow-billed Storks with gray plumage and a gray bill without a shield, but are larger.

Plumages

A description of plumage development in immature storks, particularly the onset of coloration and number of molts, is lacking.

Natal Down

Newly-hatched chicks are downy and white.

Immature

As a chick grows in the nest it develops a light gray head, neck, and back, and the underside remains white. The wing scapulars become black as in adults within the first month in the nest (3). By the time of fledging, a chick has a dark gray head, neck, and back, which are still relatively downy, and black-tipped, and white flight feathers have begun to grow. More precise information on timing of this coloration change is needed, however. More specifically, information is needed about plumage development leading up to the onset of adult coloration in the wild, as this has varied in captivity. This would be especially relevant for aging immatures in the field.

Adult

Adults have a black head, neck, upper wing coverts, tail, and upper and underwing coverts which form a longitudinal band. The flight feathers and marginal and primary coverts are white, as are the back and underside. The black feathers, especially of the head and neck, have a purple to green iridescence in certain lighting conditions. Iridescence in head and neck plumage is more pronounced during breeding, which is the only distinguishable characteristic between non-breeding and breeding plumage (4).

Molts

Pre-basic molt patterns are completely undescribed. Indeed, it is not known how many molts occur before reaching definitive basic–or even at what age this occurs.

Bare Parts

Bill

The bill is characteristically colorful and also identical in both sexes. In adults, the distal half is red, the middle third is black, and the basal fifth is a red fleshy lappet extending to the eye. The tomia (cutting edges of each mandibles) are as sharp as knives (JG), which probably helps with grasping slippery prey like fish. A yellow fleshy lappet covers the culmen; this is the namesake "saddle." The purpose of the "saddle" is not known, but it is possible it plays a role in thermoregulation given the increasing knowledge of bill morphology and its relation to heat dissipation in warm environments (5, 6, 7). Each individual stork has a unique pattern at the distal edge of the black portion of the bill, which allows individuals to be uniquely identified in mark-resight research (8, 9).

At hatching, the dorsal base of the bill is flattened where the "saddle" will grow. As immature birds grow, their dark gray bills grow longer and the base of the "saddle" becomes more pronounced. Still, the bill is shorter than adults at the time of fledging. Two males at the Forth Worth Zoo began developing yellow on the "saddle" and red at the base of the bill at just 7 months old (S. Collinsworth, personal communication). At 28 months old, siblings at the Sedgewick County Zoo had not developed at the same rate: the male had reached essentially full adult plumage and bill color while the female still retained juvenile plumage, and the red of the distal half of the bill was still developing (S. Newland, personal communication). Keepers at the Maryland Zoo observed a female reach full adult plumage and coloration at approximately 3 years old (J. Kottyan, personal communication), and a male at the Baton Rouge Zoo did so at approximately 2 years old (L. Schoen, personal communication).

Iris and Facial Skin

Eye-color varies by sex: males have a dark brown iris, while females have a yellow iris. In addition, there is usually bare skin around the eye that is red in color.

Bare Skin on Head and Chest

Below the base of the bill is a pair of yellow, sometimes red, wattles that can be found in both sexes but is usually more pronounced in males (JG). It is also possible these serve some thermoregulatory function as they can shrink into the bill in cold temperatures (JG). In addition, the chest has a bare patch of red skin that sometimes protrudes from the white feathers , possibly because it fills with air when excited (10).

Tarsi and Toes

The long legs are gray to black with pink to red tibia-tarsal joints and toes . On young still in the nest, the tibio-tarsal joints are whitish.

Measurements

Linear Measurements

The Saddle-billed Stork is one of the tallest storks at 1.5 m in height (10).

Wingspan

About 2.5 m (4).

Bill

In adults, approximately 30–33 cm in length (11, 4). At three weeks old, bill is still relatively short at 9.8 cm in length (12).

Legs

The entirety of the legs of the type specimen described by Shaw (11) measured 75 cm.

Mass

Ranges between 5–7 kg (13).

Recommended Citation

Gula, J. (2021). Saddle-billed Stork (Ephippiorhynchus senegalensis), version 2.0. In Birds of the World (S. M. Billerman and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.sabsto1.02