16-7-2024 ROTTERDAM ZOO, NETHERLANDS - GREAT WHITE PELICAN (Pelecanus onocrotalus)

The great white pelican is a huge bird—only the Dalmatian pelican is, on average, larger among pelicans. It measures 140 to 180 cm (55 to 71 in) in length with a 28.9 to 47.1 cm (11.4 to 18.5 in) enormous pink and yellow bill, and a dull pale-yellow gular pouch. The wingspan measures 226 to 360 cm (7 ft 5 in to 11 ft 10 in), the latter measurement being the highest among extant flying animals outside of the great albatross. The adult male measures about 175 cm (69 in) in length; it weighs from 9 to 15 kg (20 to 33 lb)  and larger races from the Palaearctic are usually around 11 kg (24 lb), with few exceeding 13 kg (29 lb). It has a bill measuring 34.7 to 47.1 cm (13.7 to 18.5 in). The female measures about 148 cm (58 in) in length, and is considerably less bulky, weighing 5.4 to 9 kg (12 to 20 lb), and has a bill that measures 28.9 to 40.0 cm (11.4 to 15.7 in) in length.[8] In Lake Edward, Uganda, the average weight of 52 males was found to 11.45 kg (25.2 lb) and in 22 females it was 7.59 kg (16.7 lb). In South Africa, the average weight of males was 9.6 kg (21 lb) and of females was 6.9 kg (15 lb). Thus the sexual dimorphism is especially pronounced in this species (perhaps the greatest known in any extant pelican), as at times the male can average more than 30% more massive than the female. The great white pelican rivals the kori bustard, which has even more pronounced sexual dimorphism, as the heaviest flying bird to reside in Africa (both averaging perhaps slightly heavier than the cape vulture and the wattled crane). 

There are a small few slightly heavier flying birds in the Eurasian portions of the range. Among standard measurements, the wing chord is 60 to 73 cm (24 to 29 in), the tail 16 to 21 cm (6.3 to 8.3 in), and the tarsus 13 to 14.9 cm (5.1 to 5.9 in) long. Standard measurements from different areas indicate that pelicans from the Western Palaearctic are somewhat larger than those from Asia and Africa.

The male has a downward bend in the neck and the female has a shorter, straighter beak. The plumage is predominantly white except on remiges, with a faint pink tinge on the neck and a yellowish base on the foreneck. The primary feathers are black, with white shafts at the bases, occasionally with paler tips and narrow fringes. The secondary feathers are also black, but with a whitish fringe. The upperwing coverts, underwing coverts, and tertials are white. The forehead is swollen and pinkish skin surrounds the bare, dark eyes having brown-red to dark brown irides It has fleshy-yellow legs and pointed forehead-feathers where meeting the culmen. In breeding season, the male has pinkish skin while the female has orangey skin on its face. The bill is mostly bluish grey, with a red tip, reddish maxilla edges, and a cream-yellow to yolk-yellow gular pouch. The white plumage becomes tinged-pink with a yellow patch on the breast, and the body is tinged yellowish-rosy. It also has a short, shaggy crest on the nape. The white covert feathers contrast with the solid black primary and secondary feathers. The legs are yellow-flesh to pinkish orange. Both male and female are similar, but the female is smaller and has brighter orange facial skin in the breeding season.

The juvenile has darker, brownish underparts that are palest at the rump, center of the belly, and uppertail coverts. The underwing coverts are mostly dull-white, but the greater coverts are dark and there is a dark brownish bar over the lesser coverts. The rear tertials upperwing coverts mostly have paler tips with a silvery-grey tinge on the greater secondary coverts and tertials. It has dark flight feathers, and brow-edged wings. The head, neck, and upperparts, including the upperwing coverts, are mostly brown—this is the darkest part of the neck. The facial skin and the bill, including its gular pouch, are greyish to dusky greyish. The forehead, rump, and abdomen are white, and its legs and feet are grey. Its blackish tail occasionally has a silvery-grey tinge. Its underparts and back are initially browner and darker than those of the Dalmatian pelican, and the underwing is strongly patterned, similar to the juvenile brown pelican.

The great white pelican is distinguished from all other pelicans by its plumage. Its face is naked and the feathering on its forehead tapers to a fine point, whereas other species are completely feathered. In flight, the white underwing with black remiges of the adult are similar only to those of the American white pelican (P. erythrorhynchos), but the latter has white inner secondary feathers. It differs from the Dalmatian pelican in its pure white – rather than greyish-white – plumage, a bare pink facial patch around the eye, and pinkish legs. The spot-billed pelican (P. philippensis) of Asia is slightly smaller than the great white pelican, with greyish tinged white plumage, and a paler, duller-colored bill. Similarly, the pink-backed pelican (P. rufescens) is smaller, with brownish-grey plumage, a light pink to off-grey bill, and a pinkish wash on the back.

The bird is mostly silent but has a variety of low-pitched lowing, grunting, and growling calls. The flight call is a deep, quiet croak., while at breeding colonies, it gives deep moooo calls.