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Strandberg, Roine

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Strandberg
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Roine
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    Data from: Intra-African movements of the African Cuckoo Cuculus gularis as revealed by satellite telemetry
    (2017-12-20) Iwajomo, Soladoye B.; Willemoes, Mikkel; Ottosson, Ulf; Strandberg, Roine; Thorup, Kasper
    Despite many bird species migrating regularly within the African continent, in response to rainfall and breeding opportunities, documented evidence of the spatiotemporal patterns of such movements is scarce. We use satellite telemetry to document the year round movement of an intra-African migrant breeding in the savannah zone of sub-Saharan Africa, the African Cuckoo. After breeding in central Nigeria, the birds migrated to more forested sites in the Adamawa region of Cameroon (n=2) and western Central African Republic (n=1). Departure from the breeding ground coincided with deteriorating environmental conditions whereas arrival at the non-breeding sites matched period of increasing vegetation greenness. Migratory movements generally occurred during dark hours. In total, an average distance of 748 km in 66 days was covered during the post-breeding migration and 744 km in 27 days during return journey with considerable individual variation and with more stopover sites used during post-breeding migration. The diversity of migration routes followed suggests a relatively variable or flexible initial migration strategy, high individual route consistency as well as high fidelity for non-breeding grounds.
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    Data from: Remarkably similar migration patterns between different red-backed shrike populations suggest that migration rather than breeding area phenology determines the annual cycle
    (2020-10-03) Pedersen, Lykke; Onrubia, Alejandro; Vardanis, Yannis; Barboutis, Christos; Waasdorp, Stef; van Helvert, Monique; Geertsma, Marten; Ekberg, Per; Willemoes, Mikkel; Strandberg, Roine; Matsyna, Ekaterina; Matsyna, Alexander; Klaassen, Raymond H.G.; Alerstam, Thomas; Thorup, Kasper; Tøttrup, Anders P.
    The regular fluctuation of resources across the Globe guides movements of migratory animals. To ensure sufficient reproductive output and maintain viable population sizes, migratory animals should match arrival at breeding areas with local peaks in resource availability. It is generally assumed that breeding phenology dictates the timing of the annual cycle, but this is poorly studied. Here, we use light‐level geolocator tracking data to compare the annual spatiotemporal migration patterns of a long‐distance migratory songbird, the red‐backed shrike, Lanius collurio, breeding at widely different latitudes within Europe. We find that populations use remarkably similar migration routes and are highly synchronized in time. Additional tracks from populations breeding at the edges of the European range support these similar migration patterns. When comparing timing of breeding and vegetation phenology, as a measure of resource availability across populations, we find that arrival and timing of breeding corresponds to the peak in vegetation greenness at northern latitudes. At lower latitudes birds arrive simultaneously with the more northerly breeding populations, but after the local greenness peak, suggesting that breeding area phenology does not determine the migratory schedule. Rather, timing of migration in red‐backed shrikes may be constrained by events in other parts of the annual cycle.
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    Data from: Sex-specific difference in migration schedule as a precursor of protandry in a long-distance migratory bird
    (2019-08-07) Pedersen, Lykke; Nina Munkholt, Jakobsen; Strandberg, Roine; Thorup, Kasper; Tøttrup, Anders P.
    NOTE: An updated and larger version of this dataset is available. See https://doi.org/10.5441/001/1.4bt7365c. ABSTRACT: Protandry, the earlier arrival of males at the breeding grounds relative to females, is common in migratory birds. However, due to difficulties in following individual birds on migration, we still lack knowledge about the spatiotemporal origin of protandry during the annual cycle, impeding our understanding of the proximate drivers of this phenomenon. Here, we use full annual cycle tracking data of red-backed shrikes Lanius collurio to investigate the occurrence of sex-related differences in migratory pattern, which could be viewed as precursors (proximate causes) to protandry. We find protandry with males arriving an estimated 8.3 days (SE = 4.1) earlier at the breeding area than females. Furthermore, we find that, averaged across all departure and arrival events throughout the annual cycle, males migrate an estimated 5.3 days earlier than females during spring compared to 0.01 days in autumn. Event-wise estimates suggest that a divergence between male and female migratory schedules is initiated at departure from the main non-breeding area, thousands of kilometres from, and several months prior to arrival at the breeding area. Duration of migration, flight speed during migration and spatial locations of stationary sites were similar between sexes. Our results reveal that protandry might arise from sex-differential migratory schedules emerging at the departure from the main non-breeding area in southern Africa and retained throughout spring migration, supporting the view that sex-differential selection pressure operates during spring migration rather than autumn migration.