The restricted range of the Ethiopian Bush-crow Zavattariornis stresemanni is a consequence of high reliance on modified habitats within narrow climatic limits

摘要: We attempt to describe and explain the pecu- liarly restricted distribution of globally threatened Ethiopian Bush-crow Zavattariornis stresemanni .A t a regional scale, models containing only correlates land cover suggested far wider suitable habitat in north-east Africa than area actually occupied. However, including climate variables pre- dicted known almost perfectly, sug- gested that species' occupancy is delimited by pocket cooler, dryer more seasonal surrounding areas. The predicted probability occurrence was low outside narrow range mean annual temperatures 17.5-20C. Within be climatically most suitable, records Bush-crows were concentrated 1-km cells marginally but significantly lower normalised difference vegetation index (NDVI), indicating preference for areas photosynthetic activity. At finer spatial scale within 10-km 2 intensive study site core range, nests located 30-m higher NDVI always close NDVI. These comprise open grassland, which standardised observations indi- vidual birds showed main foraging habitat. taller also necessary nesting roosting; average height from ground nearly 5 m. Therefore, appears defined primarily unique it shows park-like habitats grassland interspersed with vegetation, largely result clearance people their associated grazers. diet appeared unspecialised wide feeding methods observed. Models estimate optimal climatic around 6,000 km , perhaps 4,500 has cover. tentatively global population at least 9,000 breeding pairs, potentially larger additional non-breeding birds, particularly nest-helpers. Several predict increases both tempera- ture precipitation southern highlands Ethiopia. suggests change may therefore pose serious threat its long-term survival.