Geolocator tracking of Great Reed-Warblers (Acrocephalus arundinaceus) identifies key regions for migratory wetland specialists in the Middle East and sub-Saharan East Africa

Abstract

Wetland-dependent migratory songbirds represent one of the most vulnerable groups of birds on the planet, with .67% of wetland-obligate species threatened with extinction. One of the major hurdles for conservation efforts is determining the migration routes, stopover sites, and wintering sites of these species. We describe an annual migration cycle revealed by geolocator tracking of Great Reed-Warblers (Acrocephalus arundinaceus) breeding in the Aras River wetlands of eastern Turkey. Because of its relatively large size and breeding ground fidelity, the Great Reed-Warbler is an excellent candidate for geolocator studies and can serve as an indicator species for other wetland songbirds, many of which are particularly threatened in the Middle East. All birds made use of at least 2 wintering grounds in South Sudan, on the Indian Ocean coast and on the western shores of Lake Malawi, as well as several important stopover sites. We also identified a counterclockwise migration path into and out of Africa. Throughout the year, these birds encountered 277 Important Bird Areas, .40% of which had little or no protection. Many species of wetland songbird, particularly threatened species, may be too rare or too small to be the focus of similar studies. Our results not only allow for comparisons with other Great Reed-Warbler populations, but also reveal previously unknown stopover and wintering locations to target conservation efforts that will help wetland-dependent bird species in the Middle East and East Africa.

Autumn migration strategy of juvenile great reed warblersAcrocephalus arundinaceuson the eastern European flyway: a spatiotemporal pattern of accumulation and utilisation of energy stores

“…However, there were suggestions of autumnal long, non-refuelling flights of great reed warblers from southern Europe to their wintering grounds, based on the high numbers of birds recorded in France and Italy and their low numbers in northern Africa (Cramp & Brooks 1992;Kennerley & Pearson 2010). These long flights were confirmed recently by geolocator studies (Lemke et al 2013;Horns et al 2016;Koleček et al 2016;Hasselquist et al 2017). If so, this species may adopt the "sedge warbler-like" strategy with a few stopovers only and long non-refuelling flights across large ecological barriers (Bibby & Green 1981;Schaub & Jenni 2000a, 2000b.…”

“…The fattest birds, i.e., those with FS = 7, may potentially have been able to cover the distance of 3882 km from Bulgaria, thus reaching the Sahel zone in one non-refuelling flight bout, but they represented a very small fraction of the birds (1.2% of all birds caught at this ringing station). Individuals caught and tagged in Turkey covered the whole distance to the Sahel zone without stopping en route (Horns et al 2016;Koleček et al 2016). Our results also show that great reed warblers had sufficient energy stores to cross the Sahara in one flight from the northern Mediterranean region (single individuals even from the Balkans) without stopping at the northern African coasts to refuel.…”

“…Most studies on this species have focused on phenology of migration, fat reserves or body mass at single stopover sites (Bibby & Green 1983;Akriotis 1998;Ilieva & Zehtindjiev 2005;Zehtindjiev et al 2010;Fransson et al 2017), or on the dates of arrival to and departure from the wintering grounds (Hedenström et al 1993). Recently, new findings on the spatiotemporal migratory patterns of the great reed warbler were revealed by geolocator tracking (Lemke et al 2013;Horns et al 2016;Koleček et al 2016;Hasselquist et al 2017;Liechti et al 2018). They showed migration routes between the breeding and wintering grounds, stopover sites, and stopover duration based on a limited number of adult individuals.…”

Identifying critical migratory bottlenecks and high‐use areas for an endangered migratory soaring bird across three continents

“…If species concentrate within small geographic areas during migration, impacts at these sites could have population-level effects (Runge et al 2014). A key issue for the conservation of migratory birds, then, is the identification of important habitat throughout the annual cycle, including where individuals spend a lot of time (hereafter 'high-use areas') and/or concentrate during migration (hereafter 'bottlenecks') due to geographical, meteorological, or other factors (Limiñana et al 2012, Runge et al 2014, Horns et al 2016. The increasing availability and miniaturization of remote-tracking technologies is facilitating a boom in the study of the full annual cycles of migratory birds, which allows the identification of such critical habitat (Bridge et al 2011, Vickery et al 2014).…”

Endangered Basra Reed-warbler (<i>Acrocephalus</i> <i>griseldis</i>) recorded for the first time in Turkey (Aves: Acrocephalidae)

“…Three global migratory flyways converge on eastern Turkey (Birdlife International, 2018) and about 210 bird species migrate along the Aras River, including 90 species that breed in the area (Türkoğlu and Şekercioğlu, 2017;eBird, 2018). In particular, the reed beds support a healthy breeding population of A. arundinaceus (Horns et al, 2016), a species that cooccurs with A. griseldis in both habitat and range (Dyrcz, 2018a(Dyrcz, , 2018b. The Aras River Station provides critical data on the occurrence, abundance, phenology, and migration strategies of migratory birds in this understudied region (Horns et al, 2016).…”