Olive ibis
| Olive ibis | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Pelecaniformes (see below.) |
| Family: | Threskiornithidae |
| Subfamily: | Threskiornithinae |
| Genus: | Bostrychia |
| Species: | B. olivacea |
| Binomial name | |
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Bostrychia olivacea (Du Bus, 1838) |
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| Current extant resident distribution according to the IUCN (2012). | |
The olive ibis is a species of ibis native to dense tropical forests in central Africa.
Historically, the olive ibis was included in various genera such as Geronticus, Comatibis and Harpiprion before finally being classified among the Bostryhia. It is also related to the Madagascar crested ibis Lophotibis cristata and Geronticus ibises.
Four subspecies of this ibis are currently recognised: Bostrychia olivacea olivacea, B. o. cupreipennis, B. o. akleyorum and B. o. rothschildi. The dwarf olive ibis Bostrychia bocagei of Sao Tome was also formerly considered to be a subspecies of the olive ibis, but is now classified as a separate species due to its considerably smaller body size and different morphology
The various subspecies inhabit different regions of Africa and despite differences in size and colouration; they are still regarded as belonging to the same species. These individual subspecies probably formed by geographic isolation through expansive grasslands or seas that separate each subspecies’ forest habitat, hence preventing passage of individuals between the subpopulations. This probably also led to the formation of the dwarf olive ibis species of Sao Tome.
This relatively small ibis measures 65–75 cm in length, depending on subspecies. Recorded wing lengths in the various subspecies are 330-334mm in olivacea, 309-355mm in cupreipennis, 343-372mm in akeleyorum, and 328mm and 313mm in males and females respectively of rothschildi. The culmen in olivacea measures 95-96mm. Single male specimens of the subspecies akeleyorum, cupreipennis and rothschildi have reported culmen lengths of 108mm, 85mm and 95mm respectively; with the corresponding lengths on females being 102mm, 94mm and 90mm respectively.
Cupreipennis and rothschildi are apparently roughly equal in size, olivcea is slightly larger, and akleyorum is the largest of all subspecies and also has the longest bill. The number of available specimens of this species is however considered too small to confirm whether this pattern of size variation among the subspecies holds generally.
The adult plumage is largely dusky brown with green and bronze iridescent tinges. The head and neck are also brown, and pale stripes extend underneath the eye. The face around the orbital and loral regions is bluish black and the bill is coral red. The tail coverts and tail are dark blue. The back and rump are dusky greenish bronze. The secondary flight feathers and wing coverts stand out from the plumage through their pinkish green tinge. The colour of the legs and feet has been described as dull dark red, yellowish green or pinkish brown. The differing descriptions of soft part colourations probably refer to individuals in different stages of breeding.
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Wikipedia