Breeding prerequisites for Ortolan Bunting Emberiza hortulana in Swedish farmland with special focus on foraging

Jan Sondell,Magnus Persson,Carles Durà

doi:10.34080/os.v29.19554

Abstract

Ortolan Buntings Emberiza hortulana are rapidly decreasing in Sweden. Changes in agricultural practices are the main reason. Landscape simplification due to the removal of semi-natural elements leads to a lack of breeding habitats. Furthermore, due to intensive artificial fertiliser applications and advanced agricultural equipment and technology, crops grow both taller and denser than 50 years ago. In Kvismaren, south central Sweden, Ortolan Buntings have been studied since 2009. Here, we focus on one question: what defines a good foraging microhabitat? In 2017, nesting areas for five females and four males were identified and we did 271 feeding observations. Average foraging distance at different nests varied between 47 and 114 meters. About 70% of the foraging activities took place within crop fields. Ortolans utilized mainly unsown rows, later to be used by tractors for spraying etc. and patchy parts of standing crops. Invertebrates extracted from those areas looked dark, suggestive of ground-dwelling species. Our key management recommendation to create better microhabitats for feeding can be easily achieved by most farmers: to leave two unsown sowing rows (amounting to 0.38 m in width) for each tractor wheel to follow.

Highlights

Ortolan Buntings Emberiza hortulana have decreased in Western Europe for many decades (e.g. Stolt 1993, Vepsäläinen et al 2005, Menz & Arlettaz 2011, Naturvårdsverket 2017) including Sweden
In southern and central Sweden, Ortolan Buntings have decreased rapidly during the last decades (Ottosson et al 2012, Green et al 2018), and today less than 100 pairs remain in Sweden south of Limes Norrlandicus
This study indicates that Ortolan Buntings at Kvismaren mainly search for ground invertebrates on small areas or strips of bare soil in the spring-sown crop fields

Summary

Introduction

Ortolan Buntings Emberiza hortulana have decreased in Western Europe for many decades (e.g. Stolt 1993, Vepsäläinen et al 2005, Menz & Arlettaz 2011, Naturvårdsverket 2017) including Sweden (Ottvall et al.2008, Green et al 2018). Jiguet et al (2016a) reviewed population trends since the beginning of the millennium across 39 European countries, and found that while the populations were stable or fluctuating in six SONDELL ET AL. (2019) | FOR AGING REQUIREMENTS FOR ORTOL AN BUNTINGS | ORNIS SVECICA 29: 5–25 countries and increasing in two (Germany and Serbia), 14 out of 15 countries with decreasing population sizes were located in Northern Europe. Ortolan Buntings Emberiza hortulana have decreased in Western Europe for many decades (e.g. Stolt 1993, Vepsäläinen et al 2005, Menz & Arlettaz 2011, Naturvårdsverket 2017) including Sweden (Ottvall et al.2008, Green et al 2018). Because of the alarming situation BirdLife Sweden started a project in 2011, to identify reasons for the ortolan decline and to introduce potential management actions. The reasons for the rapid decline of ortolans were unclear for a long time (Menz & Arlettaz 2011). Changes in a variety of breeding habitats ( the agricultural areas; Wretenberg et al 2007), environmental toxins, poaching in France ( Jiguet et al 2016b), and generally high mortality during migration and in the wintering areas are some of the possible explanations (Vepsäläinen et al 2005, Menz & Arlettaz 2011, Naturvårdsverket 2017). In Finland, a population crash in the early 1990s was “associated with the amount of small-scale environmental heterogeneity and with agricultural practices” (Vepsäläinen et al 2005)

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