Rediscovery of the Black-fronted Francolin in Southern Ethiopia

In May 2012 and in May 2013 we searched for the Black-fronted Francolin Pternistis (castaneicollis) atrifrons in the Mega area in southern Ethiopia. Since most of the scarcely published records date back about seven decades, our objectives were (1) to confirm its presence at the type locality, (2) to explore other potentially suitable areas, (3) to collect information on morphology and field characteristics, behaviour

and habitat, (4) to conclude on its taxonomic position, and (5) to make a preliminary assessment of threats to the birds and their habitat. We recorded at least 12 different Black-fronted Francolin individuals on five sites around the town of Mega (04°03′28″ N 38°19′16″ E). The birds inhabited semi-open woodland between 1,480 and 2,223 m asl, where the original juniper forest has almost vanished because of heavy utilisation pressure, primarily by the expansion of agriculture, grazing and harvesting of firewood and timber. A typical external feature of the males is a clearly visible bald yellow patch behind the eye. While no other P. castaneicollis subspecies seems to have this spot, other francolin species have. Additionally, our molecular and bioacoustic data support the separate taxonomic status of atrifrons. Taking together all characters, assigning species status for the Black-fronted Francolin is justified. Based on our survey, we estimate the current population to be very small, rendering the Black-fronted Francolin the most endangered galliform bird of Africa. Also, we assume its range to be much smaller and more fragmented than previously thought, making the local populations crucially endangered.

Download the full article VERTEBRATE ZOOLOGY 64(2) 261-271

Climate and the restricted range of the Ethiopian Bush-crow

Distribution of the 4,455 1-km cells predicted to contain suitable land cover (dark blue) within 

the envelope of 6.001 1-km cells with optimal climate suitalility (light and dark blue) in southern Ethiopia. 

In a study, published in 2012 in the Journal of Ornithology*, we attempt to describe and explain the peculiarly restricted distribution of the globally threatened Ethiopian Bush-crow Zavattariornis stresemanni. At a regional scale, models containing only correlates of land cover suggested a far wider distribution of suitable habitat in north-east Africa than the area actually occupied. However, models including only climate variables predicted the known distribution almost perfectly, and suggested that the species’ area of occupancy is delimited by a pocket of climate that is cooler, dryer and more seasonal than surrounding areas. The predicted probability of occurrence was low outside a narrow range of mean annual temperatures of 17.5–20°C. Within the area predicted to be climatically most suitable, records of Bush-crows were concentrated in 1-km cells of marginally but significantly lower normalised difference vegetation index (NDVI), indicating a preference for areas of lower photosynthetic activity.  At a finer spatial scale within a 10-km2 intensive study site in the core of the species’ range, nests were located in 30-m cells of higher NDVI but always close to areas of lower NDVI. These areas of lower NDVI comprise open grassland, which standardised observations of individual birds showed to be the main foraging habitat. However, taller vegetation is also necessary for nesting and roosting; the average height of nests from the ground was nearly 5 m. Therefore, the species’ range appears to be defined primarily by a unique climate pocket within which it shows a preference for park-like habitats of grassland interspersed with taller vegetation, largely the result of clearance of vegetation by people and their associated grazers. The diet appeared unspecialised and a wide range of feeding methods was observed. Models estimate the species’ optimal climatic range to cover around 6,000 km2, of which perhaps 4,500 km2 has suitable land cover. We tentatively estimate the global population to be at least 9,000 breeding pairs, with a potentially larger additional population of non-breeding birds, particularly nest-helpers. Several climate models predict increases in both temperature and  precipitation in the southern highlands of Ethiopia. The species’ narrow climatic range suggests that global climate change may therefore pose a serious threat to its long-term survival.

* Donald, P. F., Gedeon, K., Collar N. J., Spottiswoode, C. N., Wondafrash, M. & Buchanan, G. M. 2012: The restricted range of the Ethiopian Bush-crow Zavattariornis stresemanni is a consequence of high reliance on modified habitats within narrow climatic limits. Journal of Ornithology 153: 1031-1044.

Construction and thermal insulation of Ethiopian Bush-crow nests

The main function of bird nests is to provide shelter for eggs and nestlings in order to support optimal offspring development. While this basic condition applies to all nests, an enormous constructional variety in nests has evolved. Regarding its thermal properties, the avian nest construction generally represents a compromise between heat conservation,heat dissipation, and protection from external heat.

The Ethiopian Bush-crow is an endemic Ethiopian bird species which has a very small and climatically distinct range that is cooler, dryer and more seasonal than the surrounding areas. Bush-crows build large domed nests made of thorny twigs with comparatively thick walls and a soil-lined bottom. In a preliminary study* we studied the thermal properties of a bush-crow nest with the aid of IR thermography. Our results show that there was no heat emission in the early morning and that nest surface temperatures clearly corresponded to the temperature changes during the day. Therefore we hypothesise that the nest construction provides substantial thermal insulation during the night time and presumably also delays temperature increase in the internal nesting chamber during the day time. We suggest that the bush-crow’s specific nest construction may have contributed to its persistence in the climatically unique south Ethiopian conditions.

* Töpfer, T. & K. Gedeon 2012: The construction and thermal insulation of Ethiopian Bush-crow (Zavattariornis stresemanni) nests: a prelimary study. Avian Biology Research 5 (4): 198-202.

Thermographic image of a bush-crow nest just before sunrise (a) and at noon (b).

Why share Ethiopian Bush-crow and White-tailed Swallow an identical range in spite of a very different history of colonization?

Distribution map of the three Hirundo species

There are two endemic bird species in southern Ethiopia which live in almost an identical range: Ethiopian Bush-crow and White-tailed Swallow. But apparently their respective ancestors come from very different parts of the world. The closet relatives of Zavattariornis - ground jays of the Genus Podoces - live in Central Asia, whereas the relatives of Hirundo megaensis are all from Africa. Dor et al (2010) describe the relationship of the swallows as follow:

"...the ‘Pearl-breasted Swallow’ clade, is comprised of the Pearl-breasted (Hirundo dimidiata), White-tailed (H. megaensis) and Pied-winged swallows (H. leucosoma). ... Phylogenetic relationships of the White-tailed Swallow, a species endemic to a small region in southern Ethiopia, have not been previously examined, but based on plumage traits it was expected to be close to the Pearl-breasted Swallow  (Sibley and Monroe, 1990; Turner and Rose, 1989), and our analysis confirmed this affinity. Indeed, the genetic divergence between H. megaensis and H. dimidiata (0.7%) is by far the smallest existing among species in the genus (otherwise, range = 2.0–11.6%) and is equivalent to the divergence among populations of the polytypic H. rustica (range 0.25–1.6%). H. megaensis and H. dimidiata inhabit similar habitats, but are separated by a range disjunction of about 1,500 km..."

It remains one interesting question: Why share Zavattariornis stresemanni and Hirundo megaensis a nearly identical tiny range in spite of a very different history of colonization?

Avifauna of Ethiopia: Some risk aspects

Threatened animal species in Africa (WCM/IUCN 1998) 

Many of the endemic species in the Horn of Africa live in very narrowly defined areas. 30 of 67 species in the Endemic Breeding Bird table inhabit areas of less than 20,000 square km, eight of them even in areas of 200 square km or less. Therefore, the risk potential of these species must be assessed as high. Regional and even local changes in land use or climate conditions can have serious consequences for the development and survival of small populations.

According to IUCN, 17 of the 67 endemic bird species are considered as "endangered", three of them as "critical endangered": Ochre-brested Francolin (Francolinus ochropectus), Archers's Lark (Heteromirafra archeri) and Liben Lark (Heteromirafra sidamoensis). The latter exists only in an approximately 30-acre area in southern Ethiopia. The total population size is estimated to be less than 250 individuals (Donald et al. 2010). If no protection measures are implemented in the near future, we will probably witness its extinction. Encouraging are recent observations from May 2011, after which the species occurs in another small area in north eastern Ethiopia (Nigel Collar, oral information). Genetic studies should also clarify whether H. archeri and H. sidamoensis are actually different taxa.

Looking at the birds of the African continent as a whole, the avifauna of Eastern Africa (including Horn of Africa and offshore islands) is particularly at risk. Back in the nineteen nineties, 107 bird species in that area were threatened according to IUCN criteria (critical endangered, endagered or vulnerable ). That's more than 50% of then 207 threatened bird species in Africa (WCM / IUCN 1998).

Avifauna of Ethiopia: Some unsolved taxonomic questions

Ethiopian Boubou (Laniarius aethiopicus)

Numerous taxonomic questions of birdlife in the Horn of Africa region will require further clarification or have been investigated only recently.

This concerns at least eight of the taxa listed in the Endemic Breeding Bird table. The Socotra Buzzard (Buteo socotraensis) is according to genetic findings closest related to Buteo bannermanni, who lives on the Cape Verde islands. Valid nomenclatural description was not done until recently (Jennings 2010, Porter and Kirwan 2010). Buteo archeri, living in Somalia, is often regarded as a subspecies of Buteo augur. Further studies to define the populations are lacking. Otus socotranus (described 1899) is seen again as a separate species after long lumped with O. senegalensis (Jennings, l.c.). The re-separation of Laniarius erlangeri (described 1905) of L. aethiopicus was only recently (Nguembock et al. 2008). In this context the Bulo Burti Boubou (L. liberatus), described in 1991 by Smith et al., was recognized as a morph and the species status withdrawn. Calandrella erlangeri (described 1905) was long regarded as subspecies of Calandrella blanfordi. Dowsett and Forbes-Watson (1993) united C. somalica, C. athensis and C. erlangeri to C. somalica. However, Clements (2000) regarded C. erlangeri again as separate species. While Redman et al. (2009) follow the suggestion, Ash and Atkins (2009) treat erlangeri again as a subspecies of C. blanfordi. A final clarification seems open. The Degodi Lark is no longer a valid species (Collar et al. 2009).

The range of the Ethiopian Bush-crow in southern Ethiopia

Ethiopian Bush-Crow (Zavattariornis stresemanni)

In July 2010 we made a survey on the endemic Ethiopian Bush-crow Zavattariornis stresemanni in southern Ethiopia (Oromia Regional State, Borana zone). Along a 2,500 km-long track about 500 GPS-based records on birds and nest sites were collected. We counted a total of 2,600 birds or nests. Previous studies on the range of the Ethiopian Bush-crow were largely limited to countings along the paved roads and on random observations. With the data now available, it is possible to estimate the range of the species more reliably. We found birds or nests in 81 grids (5x5 minutes fields). This corresponds to an area of ​​approximately 7,000 sq. km. Thus, the range of the species is larger than thought. Previous estimates were 4,600 sq. km (BirdLife International species factsheed, July 2011). The results can be found in the following maps.

Map of the track and records
Distribution map (grid map, with a grid size of 5 minutes)
Map of the main breeding areas
Density map 

We are currently working on a model that explains the limited range of the species based on data on climate and vegetation. A publication is being prepared. I am grateful to Deutsche Ornithologen-Gesellschaft (DO-G) and Gesellschaft für Tropenornithologie (GTO) for funding. 

Endemic Birds on the Horn of Africa

Ethiopia is characterized by a great topographic and landscape diversity. The height profile varies from 125 meters below sea level in the Danakil desert to the 4,533 m high summit of Ras Dejen in the Simien mountains. With an area of 1,127 million km² Ethiopia is something three times as large as Germany, with a comparable population of currently around 85 million. The peculiarity of the Ethiopian avifauna can be judged better when viewed in a somewhat wider context. As a spatial reference point should serve the "Horn of Africa", in addition to Ethiopia including its neighbors Eritrea, Djibouti and Somalia, as well as the Socotra Archipelago (short Socotra), lying off the Somali coast, but politically belonging to Yemen.

In this region more than 1,000 nesting and migratory bird species were noted. In the Endemic Breeding Birds table overall 67 species or taxonomic units are listed, which may be awarded the status of "endemic" on the Horn of Africa. Such a list is always provisional and can not offer more than a basis for discussion. This is due to the fact that a number of taxonomic and nomenclatural issues are still unclear. New findings inevitably lead to other perspectives and revised figures. Secondly, there is always a certain discretion whether to record a species with very small area units (or occasional occurrence) in neighboring countries in such a list or not. The table includes the IUCN Red List category, population size and trend for each species.