This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be small, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Bostrychia olivacea (Sibley and Monroe 1990, 1993) has been split into B. olivacea and B. bocagei following Collar and Stuart (1985). Dwarf Olive Ibis Bostrychia bocagei of São Tomé differs from African Olive Ibis B. olivacea of West and Central Africa in size (wing of cupreipennis 309-355 mm, bill 83-94 mm, tarsus 58-70 mm, tail 125-133 mm [measurements of Príncipe race rothschildi similar]; wing of bocagei 248 mm [n=5] [i.e. 75%], bill 73 mm [82%], tarsus 52 mm [81%], tail 95 mm [74%]), bill colour (pale brown with pale red on culmen and tip vs all pale to brick red in rothschildi), and coloration of upperparts (lacking greenish and some bronze sheen of other races), plus an evident but still poorly documented difference in voice (rothschildi producing a typical "HAAN-ha HAAN-ha" at dawn and dusk, bocagei remaining mostly silent but occasionally delivering a more equally stressed "kàh-gàh kàh-gàh"). There is good precedent for allowing its specific status (i.e. Chapin 1923, Amadon 1953, de Naurois 1973).
Hancock, J. A.; Kushlan, J. A.; Kahl, M. P. 1992. Storks, ibises and spoonbills of the world. Academic Press, London.
Brown, L. H.; Urban, E. K.; Newman, K. 1982. The birds of Africa vol I. Academic Press, London.
del Hoyo, J.; Elliott, A.; Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.
Further web sources of information
Hear sounds for this species from xeno-canto, the community database of shared bird sounds from around the world.
Text account compilers
Butchart, S., Ekstrom, J., Malpas, L.
IUCN Red List evaluators
Butchart, S., Symes, A.
BirdLife International (2013) Species factsheet: Bostrychia olivacea. Downloaded from http://www.birdlife.org on 23/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/05/2013.
This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.
To provide new information to update this factsheet or to correct any errors, please email BirdLife
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|Current IUCN Red List category||Least Concern|
|Family||Threskiornithidae (Ibises and spoonbills)|
|Species name author||(Du Bus De Gisignies, 1838)|
|Population size||3000-45000 mature individuals|
|Distribution size (breeding/resident)||802,000 km2|
|Links to further information|
|- Additional Information on this species|