Identifying migration routes and non-breeding staging sites of adult males of the globally threatened Aquatic WarblerAcrocephalus paludicola

Abstract

SummaryBirds that are long-distance migrants partition their annual cycle among a number of locations over a large spatial range. The conservation of these species is particularly complex because it requires attention to a number of different and distant habitats based on knowledge of migratory phenology, routes and staging areas. In the case of the globally threatened Aquatic Warbler Acrocephalus paludicola, a habitat specialist that breeds in Europe and spends the boreal winter in sub-Saharan Africa, non-breeding staging areas were widely unknown until recently. We applied light-level geolocators to adult male Aquatic Warblers at breeding sites in Belarus and Ukraine. Data from eight retrieved geolocators confirmed a south-west and then westward migration route through Europe via the northern Mediterranean with staging sites on the Iberian Peninsula and occasionally France and north-west Africa. In sub-Saharan Africa, final staging areas were in Mali, either in the Inner Niger Delta or at (presumably) small water bodies in the desert, with one bird most likely staying in the north of Ivory Coast south of the previously assumed range. The birds probably stayed in the final staging areas for most of the non-breeding season, but the logger on only one bird provided data throughout the entire migration cycle. Pre-nuptial migration of the latter was by a more easterly route than the southward migration. Our study suggests that conservation strategies for Aquatic Warbler north of the Sahara should include consideration of unknown staging sites in the northern Mediterranean as well as on the Iberian Peninsula and in north-west Africa. South of the Sahara, our study demonstrates the importance of the Sahel for the conservation of the Aquatic Warbler, including both the major floodplains of the Niger River and small Sahelian wetlands that are under pressure from human development.

Broad‐scale patterns of the Afro‐Palaearctic landbird migration

“…In some species, extension of their breeding ranges while maintaining the genetically imprinted direction of migration and non‐breeding areas has led to more complex migratory networks with longer migration distances, hence higher costs of migration. For example, the aquatic warbler, Acrocephalus paludicola , has gone extinct in Western Europe, and the entire world population is now breeding in eastern Europe but maintaining the historical migration route for the species along the Western flyway to their non‐breeding areas in West Africa (Salewski et al, ). Likewise, the breeding range of the pied flycatcher, Ficedula hypoleuca , extends to 93° E, and virtually the entire Palaearctic population migrates through the Iberian Peninsula along the Western flyway (Lundberg & Alatalo, ).…”

Weak migratory connectivity, loop migration and multiple non‐breeding site use in British breeding Whinchats Saxicola rubetra

“…Coordinates for non‐breeding locations were then estimated using the ‘siteEstimate’ function in GeoLight (Hiemer et al 2018, Salewski et al 2019). This method of geolocation estimates one location and its precision for each stationary period, rather than location estimates for each twilight time or pair of twilights.…”

The conservation of Afro‐Palaearctic migrants: What we are learning and what we need to know?

“…Tracking studies provide information on migration routes and strategies, and the location of wintering and stopover sites. This is fundamental information for conservation, helping to identify potential threats and drivers of decline (Rodriguez-Ruiz et al 2019, Burgess et al 2020, key sites to protect (Horns et al 2016, Buechley et al 2018, Salewski et al 2019also, Tonra et al 2019), or to target detailed ecological studies. Almost half of these studies (101) were judged to have contributed significant information for conservation.…”

“…Trierweiler et al 2014, Sara et al 2019), stopovers (e.g. van der Winden et al 2014, Salewski et al 2019) and non-breeding areas (e.g. , Finch et al 2015, Ouwehand et al 2016.…”