Distribution, abundance and habitat preferences of White-tailed Swallow Hirundo megaensis and Ethiopian Bush-crow Zavattariornis stresemanni, two southern Ethiopian endemics

Abstract

SummaryThe Yabelo-Mega region of southern Ethiopia's Borana region holds two threatened endemic and restricted-range species, the White-tailed Swallow Hirundo megaensis ('Vulnerable') and Ethiopian Bush-crow Zavattariornis stresemanni ('Endangered'). Concern about these species' conservation status has recently increased owing to rapid alterations to their thornbush savanna habitat. This six-week field study aimed to identify the specific habitat requirements of each species, with a view to understanding how they are likely to be affected by these changes, and to provide baseline quantitative abundance data using simple and repeatable methods. White-tailed Swallows were recorded on an overall 4.7% of transects and point counts, and in all habitats (including villages and farmland) except broadleaved Combretum-Terminalia woodland. Line transects indicated that swallows avoided dense scrub and tree cover, but this was not detected during point counts. Bush-crows were recorded on an overall 16.6% of transects and point counts, and like swallows showed a strong preference for thornbush (Acacia and Commiphora) over broadleaved woodland, avoided dense scrub cover, and were particularly frequent in the vicinity of villages. During point-counts, bush-crows were more frequently encountered inside the nominally protected Yabelo Sanctuary, whereas the reverse was true for White-tailed Swallows. Recent concern about dramatic declines in bush-crow numbers revealed by roadside counts may have been exacerbated by habitat alteration along roads alone, but the species remains under threat from habitat transformation through agricultural expansion, tree felling and bush encroachment.

Rangeland degradation is poised to cause Africa's first recorded avian extinction

“…From a conservation perspective, rangeland degradation is an insidious and relatively unspectacular form of anthropogenic habitat transformation that has received relatively little attention. This study demonstrates that it may soon cause Africa's first modern bird extinction, while elsewhere in southern Ethiopia bush encroachment has recently been identified as a threat to the endemic Ethiopian bush-crow (Borghesio & Giannetti, 2005) and perhaps whitetailed swallow (Mellanby et al, 2008). Thus a problem whose social dimensions have preoccupied numerous agroscientists and development agencies may also have ramifications for unique wildlife assemblages.…”

Climatic change and extinction risk of two globally threatened Ethiopian endemic bird species

“…We collated all available geo-referenced records of White-tailed Swallows and their nests, collected by various observers between 2005 and 2011 [ 30 , 36 , 37 ], including sightings made during fieldwork on the bush-crow [ 29 ]. Nests are usually built in the traditional huts occupied by local people and take the form of mud cups typical of the genus Hirundo , but in the absence of adult birds can be distinguished from sympatric hut-nesting swallows by their simple grass lining and unmarked white eggs [ 37 ].…”

“…The apparent range limitation by maximum temperature may be linked to the effects of ambient temperature on thermoregulatory and foraging behaviour [ 12 ]. The small, non-migratory White-tailed Swallow has a global distribution very similar to that of the bush-crow [ 30 , 31 ]. Several authors have noted its peculiarly restricted distribution [ 32 – 34 ], which Collar and Stuart [ 35 ] suggested might be linked to the 1,500 m altitudinal contour [ 35 ].…”

Behavioural thermoregulation and climatic range restriction in the globally threatened Ethiopian Bush‐crow Zavattariornis stresemanni

“…We collated geo‐referenced sightings of Bush‐crows made by various observers between 2005 and 2011 (Gedeon , Mellanby et al . , Donald et al . ) and added our own recent observations of all three species (2012–2015) to produce a dataset of known presences.…”