Hewson, Chris

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  • Data package
    Data from: Loop-migration and non-breeding locations of British breeding Wood Warblers Phylloscopus sibilatrix
    (2022-11-22) Burgess, Malcolm D.; Castello, Joan; Davis, Tony; Hewson, Chris
    Capsule: British breeding Wood Warblers Phylloscopus sibilatrix show a clockwise loop migration incorporating stops in southern Europe, the Sahel, and the humid forest zone of West Africa. Aims: To determine autumn and spring migration routes, the location and duration of stopover sites on migration, and the location of non-breeding areas of British breeding Wood Warblers. Methods: In 2016 and 2018 we deployed geolocators to male Wood Warblers on Dartmoor, Devon, and in the New Forest, Hampshire. We retrieved four geolocators from returning birds in 2017, 2019, and 2020. Results: Male Wood Warblers departed breeding sites in late July and stopped for most of August in central southern Europe, crossed the Sahara by a non-stop night and day flight immediately followed by a short stop, and then migrated west to a longer stopover in the Sahel. Final non-breeding destinations were in an area of West Africa covering Guinea, Sierra Leone, and Liberia. Two were tracked on spring migration, again crossing the Sahara via a non-stop flight before migrating through Western Europe to complete a clockwise loop migration back to Britain. Conclusion: All tracked Wood Warblers used stopovers for at least three weeks in three distinct regions, in central southern Europe, in the Sahel, and in the humid zone of West Africa. Although the limitations of geolocation prevent matching locations with habitat, these regions are broadly characterized by distinct forest or woodland habitat types, which differ from breeding habitat. All four tracks showed similar patterns in route, stopover behaviour, and timings, suggesting they may be representative of males in these breeding populations, and potentially of other British and western European Wood Warbler populations.
  • Data package
    Data from: A pan-European, multi-population assessment of migratory connectivity in a near-threatened migrant bird
    (2015-07-22) Finch, Tom; Saunders, Philip; Catry, Inês; Mardega, Ieva; Mayet, Patrick; Račinskis, Edmunds; Sackl, Peter; Schwartz, Timothée; Tiefenbach, Michael; Hewson, Chris; Franco, Aldina; Butler, Simon James
    Aim: The extent to which individuals from different breeding populations mix throughout the non-breeding season (i.e. ‘migratory connectivity’) has important consequences for population dynamics and conservation. Given recent declines of long-distance migrant birds, multi-population tracking studies are crucial in order to assess the strength of migratory connectivity and to identify key sites en route. Here, we present the first large-scale analysis of migration patterns and migratory connectivity in the globally near-threatened European roller Coracias garrulus. Location: Breeding area: Europe; passage area: Mediterranean, sub-Saharan Africa, Arabian Peninsula; wintering area: southern Africa Methods: We synthesise new geolocator data with existing geolocator, satellite tag and ring recovery data from eight countries across Europe. We describe routes and stopover sites, analyse the spatial pattern of winter sites with respect to breeding origin, and quantify the strength of connectivity between breeding and winter sites. Results: We demonstrate the importance of the northern savannah zone as a stopover region and reveal the easterly spring loop (via Arabia) and leap-frog migration of rollers from eastern populations. Whilst there was some overlap between individuals from different populations over winter, their distribution was non-random, with positive correlations between breeding and autumn/winter longitude as well as between pairwise distance matrices of breeding and winter sites. Connectivity was stronger for eastern populations than western ones. Main conclusions: The moderate levels of connectivity detected here may increase the resilience of breeding populations to localised habitat loss on the winter quarters. We also highlight passage regions crucial for the successful conservation of Roller populations, including the Sahel/Sudan savannah for all populations, and the Horn of Africa/Arabian Peninsula for north-eastern rollers.