14-10-2015 VALENCIA BIOPARC - YELLOW BILLED STORK (Mycteria ibis)

The yellow-billed stork (Mycteria ibis), sometimes also called the wood stork or wood ibis, is a large African wading stork species in the family Ciconiidae. It is widespread in regions south of the Sahara and also occurs in Madagascar.

his medium-sized stork stands 90–105 cm (35–41 in) tall. Its body is white with a short black tail that is glossed green and purple when freshly moulted. The bill is deep yellow, slightly decurved at the end and with a rounder cross-section than in other stork species outside the Mycteria. Feathers extend onto the head and neck just behind the eyes, with the face and forehead being covered by deep red skin. Both sexes are similar in appearance, but the male is larger and has a slightly longer heavier bill. Males and females weigh approximately 2.3 kg (5.1 lb) and 1.9 kg (4.2 lb) respectively.

Colouration becomes more vivid during the breeding season. In the breeding season, the plumage is coloured pink on the upperwings and back; the ordinarily brown legs also turn bright pink; the bill becomes a deeper yellow and the face becomes a deeper red.

Juveniles are greyish-brown with a dull, partially bare orange face and a dull yellowish bill. The legs and feet are brown and feathers are blackish-brown all over. At fledging, salmon-pink colouration in the underwings begins to develop and after about one year, the plumage is greyish-white. Flight feathers on the tail and wing also become black. Later, the pink colouration typical of adult plumage appears.

These storks walk with a high-stepped stalking gait on the ground of shallow water. Their approximate walking rate has been recorded as 70 steps per minute. They fly with alternating flaps and glides, with the speed of their flaps averaging 177–205 beats per minute. They usually flap only for short journeys and often fly in a soaring and gliding motion over several kilometres for locomotion between breeding colonies or roosts and feeding sites. By soaring on thermals and gliding by turns, they can cover large distances without wasting much energy. On descending from high altitudes, this stork has been observed to dive deeply at high speeds and flip over and over from side to side, hence showing impressive aerobatics. It even appears to enjoy these aerial stunts.

This species is generally non-vocal, but will utter hissing falsetto screams during social displays in the breeding season. These storks also engage in bill clattering and an audible “woofing” wing beat at breeding colonies Nestlings make a loud continual monotonous braying call to beg parental adults for food.