The green ibis (Mesembrinibis cayennensis), also known as the Cayenne ibis, is a wading bird in the ibis family Threskiornithidae. It is the only member of the genus Mesembrinibis.
This is a resident breeder from Honduras through Nicaragua, Costa Rica and western Panama, and South America to northern Argentina. It undertakes some local seasonal movements in the dry season.
The green ibis was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it in the genus Tantalus and coined the binomial name Tantalus cayennensis.[2] Gmelin based his description on the "Cayenne ibis" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds .[3] Latham had based his own description on the "Le Courlis des Bois " and the "Courly vert, de Cayenne" that the French polymath, the Comte de Buffon had included in his Histoire Naturelle des Oiseaux.[4][5] The green ibis is now the only species placed in the genus Mesembrinibis that was introduced in 1930 by James Lee Peters.[6][7] The genus name Mesembrinibis is a combination of the Greek word mesēmbrinos, meaning "southern" (from mesēmbria, meaning "south") and ibis. The specific epithet cayennensis means "of Cayenne or French Guiana".[8] The species is monotypic: no subspecies are recognised.[7] The species is also sometimes known as Cayenne ibis.[9]
DNA–DNA hybridization studies show that the species falls squarely into the New World ibis clade, with its closest relatives being the sharp-tailed ibis, the American white ibis and the buff-necked ibis.[10]
The green ibis is a medium-sized ibis, with short legs and a long, slender, decurved bill.[11][12] It measures 45–60 cm (18–24 in) in length and ranges from 700 to 890 g (1.5 to 2.0 lb) in mass.[13] The sexes, which are identical in plumage, overlap somewhat in measurements, though the largest birds are male.[13] Breeding adults have glossy greenish-black bodies, pale green legs and bill, and grey bare facial skin patches. Juveniles are much duller, but can be distinguished from the similar glossy ibisby their bulkier shape, shorter legs and broader wings. This species, like other ibises, flies with neck outstretched. Its flight is heavy, with fewer glides and jerkier wingbeats than its relatives.
It has a hollow, hooting, accelerating call,[14] most often heard at dawn and dusk.[15] Transcribed as kro kro or koro koro, the call is described as "mellow".[15]