Justification of Red List Category
This species's population was believed to be declining very rapidly as a result of habitat alteration within its small range, and it is therefore listed as Endangered. Despite more recent evidence which indicated that the population may be stable, the species's tight climatic limitation places it under threat from climate change.
Based on nest-counts, and remotely-sensed habitat availability, Donald et al. (2012) estimate a global population of at least 9,000 breeding pairs, however, some areas assessed as suitable do not contain any birds, so this may be an overestimate (A. Bladon in litt. 2016). As active nests typically have several nest-helpers there may be a significant additional non-breeding population. It is placed here in the band 10,000-19,999 mature individuals.
Encounter rates in the Yavello Wildlife Sanctuary declined by 80% between 1989 and 2003 (Borghesio and Giannetti 2005), which covers a large part of the species's range, and declines are presumed to be continuing, owing to on-going habitat conversion and degradation. The overall rate of decline is estimated to be very rapid. More recent studies suggest that the species's population in fact may be stable (P. Donald in litt. 2012), however a rapid ongoing decline is retained here until this can be confirmed; and the species is suspected to be vulnerable to climate change (Bladon et al. in prep.).
Zavattariornis stresemanni is confined to the area around Yabello, Arero, and Mega, in southern Ethiopia. Part of the species's range, incorporates the former Yabello Wildlife Sanctuary, which has recently been upgraded to the Yabello National Park (Borghesio and Giannetti 2005, EWCA 2016). It has a highly restricted distribution, occurring only patchily within an area that extends just 160 km from north to south and less than 100 km from east to west (Donald et al. 2012). The species’s area of occupancy appears to be defined by a unique climate pocket that is cooler, dryer and more seasonal than the surrounding area (Donald et al. 2012). Within this limited climate window it favours a park-like landscape of grazed pasturelands interspersed with taller vegetation (Gedeon 2006). Models predict an area of just 6,000 km2 to be climatically optimal, of which perhaps 4,500 km2 has suitable vegetation (Donald et al. 2012). There is no historical data on the population size or distribution of the species but brief surveys in 1989 suggested densities had remained constant through the 1980s. Surveys in 1996 found the species to be common within its restricted range (EWNHS 1996). However, 80% declines in encounter rates on roadside counts in the Yabello Wildlife Sanctuary between 1989 and 2003, suggested that the population was decreasing very rapidly (Borghesio and Giannetti 2005), although doubt has been expressed about the severity of these apparent declines (Mellanby et al. 2008, Donald et al. 2012) and local people report that the population has remained stable (P. Donald in litt. 2012).
It is found in open, semi-arid areas of short-grass savanna with scattered Acacia bushes at c.1,700 m (EWNHS 1996), and is common in the vicinity of human settlements (P. Robertson in litt. 1998, Gedeon 2006). It feeds mostly on arthropods (Gedeon 2006, Donald et al. 2012) and, outside the breeding season, is gregarious (EWNHS 1996). It mainly feeds by extracting pupae and larvae from soil or from under cattle dung; however it also feeds on flying insects such as Lepidoptera, and may search for larvae in rotten branches and pick parasites from cattle (Gedeon 2006). It also has a wide range of display, contact and alarm calls (Bladon et al. 2016). The species exhibits a range of complex behaviours, including play, allopreening, allofeeding, cooperative nesting and sentinel duty (Gedeon 2006). Breeding takes place between March and June in response to the main rainy season, but has also been recorded in October/November during the smaller rains, although the consistency of the latter season is not known (Bladon et al. 2016). The species breeds cooperatively with at least one, but possibly up to four, extra-pair individuals, which each may help more than one nesting pair (Gedeon 2006). The normal nest-site is in the top of an Acacia bush (2.5-15 m high; mean 8.9m), but nests have recently been recorded on two man-made structures; a telegraph pole and an electricity pylon - at c.25m, the highest recorded nest (Bladon et al. 2016). The nest is a robust structure of Acacia twigs lines with dung, which creates a thermally stable environment (Töpfer and Gedeon 2012). Clutch-size is up to six. Breeding pairs range for about 2 ha during nest building (Gedeon 2006), and even post-fledging groups remain relatively site-faithful (Bladon et al. 2016).
Analysis of satellite imagery between 1986 and 2002 indicates that there was been an increase in vegetation density in Yabello Wildlife Sanctuary through bush encroachment, probably as a result of increased grazing pressure from livestock, the enforcement of fire suppression in the sanctuary and the disappearance of wild herbivores (Borghesio and Giannetti 2005). As the species prefers more open habitat, this is likely to be a cause of population declines. Political and administrative intervention has encouraged more maize cultivation in the species's range, in an effort to develop a monetary economy and promote self-sufficiency and the constitution of food stocks in an area that was dominated by nomadic pastoralism 10-20 years ago (Gedeon 2006). Expanding cultivation is thought to have caused population decreases near Mega (Borghesio and Giannetti 2005), and is driving the large-scale clearance of Acacia stands near Derido and Yabello (Gedeon 2006). The partial clearance of dense Acacia scrub to allow grass-growth for cattle does not appear to have affected the species and may even benefit it (P. Robertson in litt. 1998). However, some research indicates that tall Acacia bushes, in which this species nests, are being cleared intensively (for both firewood and grazing land), and this may now be having a negative impact on the species (A. Shimelis in litt. 1999). Acacia stands in areas surrounding villages tend to occupy land that is particularly suitable for cultivation, and with a rapid increase in the human population, the continued loss of the species's habitat is predicted (Gedeon 2006). Over recent years Yabello has become an administrative centre for the Borana Zone, with a continually expanding residential area, signifying human population growth and land use changes in an important area for the species (Gedeon 2006). Construction of larger roads through the region since 2012 have undoubtedly damaged the habitat in their immediate vicinity, but the extent of their impact is unknown. Protection of a larger area within the species's range under the new Yabello National Park should be of benefit to the species, but this needs to be supported by habitat management and protection in order to be effective (A. Bladon in litt. 2016), and must not exclude low intensity cattle grazing which generates the open habitat preferred by this species (Donald et al. 2012). However, given the species’ specialised climatic requirements, the greatest threat to its long-term survival is likely to be climate change (Donald et al. 2012, Bladon et al. in prep.).
Conservation Actions Underway
A detailed study of the species's distribution, ecology and likely responses to climate change is currently being compiled (Bladon et al. in prep.), and in 2012 a detailed study of its likely responses to climate change will commence. Yabello Wildlife Sanctuary, which was designated in 1985, has recently been replaced by Yabello National Park, the boundary of which has yet to be finalised (EWCA 2016). Current management plans for the new National Park aim to promote sustainable resource management across the wider landscape and strict formal protection at key sites (Donald et al. 2012). A species management plan is in the process of being written as part of a wider project on southern Ethiopian endemic birds.
30 cm. Small, starling-like crow. Pale grey head and body. Black wings and tail. Bare, blue skin around eye. Sexes similar, juvenile slightly more dingy. Similar spp. Non-breeding Wattled Starling Creatophora cinerea is much smaller, with pale rump. Voice Harsh, rasping calls and chattering. Hints Occurs in groups of 4-10, often in association with White-crowned Starling Spreo albicapillus. Common in Acacia savanna north, south and east of Yabello town, southern Ethiopia.
Text account compilers
Ekstrom, J., Harding, M., Shutes, S., Starkey, M., Taylor, J., Allinson, T, Symes, A. & Westrip, J.
Borghesio, L., Robertson, P., Shimelis, A., Wondafrash, M., Donald, P. & Bladon, A.
BirdLife International (2020) Species factsheet: Zavattariornis stresemanni. Downloaded from http://www.birdlife.org on 14/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/08/2020.