Unravelling migration connectivity reveals unsustainable hunting of the declining ortolan bunting

Abstract

In France, illegal hunting of the endangered ortolan bunting Emberiza hortulana has been defended for the sake of tradition and gastronomy. Hunters argued that ortolan buntings trapped in southwest France originate from large and stable populations across the whole of Europe. Yet, the European Commission referred France to the Court of Justice of the European Union (EU) in December 2016 for infringements to legislation (IP/16/4213). To better assess the impact of hunting in France, we combined Pan-European data from archival light loggers, stable isotopes, and genetics to determine the migration strategy of the species across continents. Ortolan buntings migrating through France come from northern and western populations, which are small, fragmented and declining. Population viability modeling further revealed that harvesting in southwest France is far from sustainable and increases extinction risk. These results provide the sufficient scientific evidence for justifying the ban on ortolan harvesting in France.

Desert crossing strategies of migrant songbirds vary between and within species

“…For all species and individuals with coordinates estimated even during equinox periods, previous and subsequent stationary areas, as determined from light intensity data 13 , were always north and south of a desert (Fig. 7), the Sahara for individuals using the western and central flyways (ten species), or the Arabian desert for ortolan buntings using the eastern flyway 14 . Table S1 reports the first and last dates with FLP for each species and season (with individual details in Table S2).

Figure 7Stationary sites of individual birds (median ±25th/75th or 20th/80th percentiles of location estimates) just prior and after the occurrence of the full light pattern(s) detected during autumn ( a – d ) and spring ( e – h ) migration; red = ortolan bunting ( a , e ); light blue = spotted flycatcher, dark blue = Mediterranean flycatcher (b,f); light green = willow warbler, dark green = wood warbler ( c , g ); orange = Eurasian reed warbler, dark red = rufous-tailed scrub-robin ( d , h ).

…”

Population‐specific migratory strategies of Twite Linaria flavirostris in Western Europe

“…, Jiguet et al . ). Non‐breeding movements in migratory birds are thought to be flexible in response to habitat and resource availability, and therefore result in differing strategies between populations.…”

“…The strength of migratory connectivity varies between species (Finch et al 2017) and, although within-species disparities in migration strategy, or migratory divides, are less well understood, they are probably common (van Bemmelen et al 2019, Jiguet et al 2019. Non-breeding movements in migratory birds are thought to be flexible in response to habitat and resource availability, and therefore result in differing strategies between populations.…”

“…Variation in migratory connectivity has potentially important consequences for population plasticity to environmental change (Cresswell ), particularly in fragmented populations which may respond asynchronously to habitat loss, climatic change (Esler ) or persecution (Jiguet et al . ).…”

“…Strong or high connectivity describes a situation of different populations maintaining separate nonbreeding sites through the annual cycle, whereas weak or low connectivity occurs when different breeding populations use similar non-breeding sites for some part of the annual cycle (Cohen et al 2017). Variation in migratory connectivity has potentially important consequences for population plasticity to environmental change (Cresswell 2014), particularly in fragmented populations which may respond asynchronously to habitat loss, climatic change (Esler 2000) or persecution (Jiguet et al 2019).…”