Habitat preferences of the Ortolan Bunting (Emberiza hortulana) in its prime wintering grounds, the cereal‐dominated Ethiopian Highlands

Jérémy Gremion,Raphaël Arlettaz,Philippe Christe,Mihret Ewnetu,Gabriel Marcacci,Tolera Sori,Fanuel Kebede,Alain Jacot,Julien Mazenauer

doi:10.1111/ibi.12992

Abstract

Agricultural intensification and land‐use changes are major factors impacting farmland biodiversity. The Ortolan Bunting Emberiza hortulana is the long‐distance trans‐Saharan migratory passerine that has undergone the most dramatic decline among all European farmland birds. The factors responsible for this decline may originate from the breeding grounds, migration stopovers and/or overwintering quarters. Very little is known about conditions on the species' wintering grounds, but a recent study has highlighted the utmost importance of the traditionally managed agroecosystems in the Ethiopian Highlands as a key wintering area, apparently harbouring as much as 90% of the world's Ortolan Bunting population. Using radiotracking and line transect surveys, this study aimed to provide fine‐grained information about species–habitat relationships in the Ortolan Bunting overwintering quarters. Our results showed the importance, at the landscape scale, of small‐scale agriculture, notably of traditionally managed, cereal‐dominated fields interspersed with semi‐natural structures. At a foraging‐site scale, on the other hand, patches of bare ground in combination with large areas of post‐harvesting stubble represented key habitat features. Stubbles provide an essential food resource and bare ground promotes ground foraging by enhancing food accessibility. The maintenance of a traditional agricultural economy will be essential to maintain the habitat potential for the Ortolan Buntings overwintering in the Ethiopian Highlands and will be instrumental in preserving its world population from further decline.

Highlights

The increasing human population weighs on ecosystems and causes habitat loss and degradation (Cardinale et al 2012)
The Ortolan Bunting Emberiza hortulana is the only long-distance migrant among the Old World buntings (Emberizidae, Cramp & Perrins 1994) that migrates to sub-Saharan Africa and is exhibiting a strong decline, estimated at 89% between 1980 and 2014 (Keller et al 2020)
Ortolan Buntings foraged significantly more often in traditional, manually harvested, fields (0.32, CI95 = 0.19–0.47) compared with fields harvested with machines (0.06, CI95 = 0.0082–0.22; Fig. 2d)

Summary

Introduction

The increasing human population weighs on ecosystems and causes habitat loss and degradation (Cardinale et al 2012). The eastern flyway is used by birds breeding in a vast area ranging from Belarus over southern Russia, including the Balkan countries and down to Turkey until western Kazakhstan (Jiguet et al 2019). These birds represent 90% of the global Ortolan Bunting population and overwinter in the cereal-dominated highlands of Eritrea and Ethiopia (Jiguet et al 2019). In a recent study it has been demonstrated that only a few bird species benefit from those newly established open landscapes created by large-scale farming, and that avian abundance and diversity are significantly higher in traditionally managed smallscale fields (Marcacci et al 2020)

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