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  • 1.
    Alerstam, Thomas
    et al.
    Lund University.
    Bäckman, Johan
    Lund University.
    Johanna, Grönroos
    Kristianstad University, Faculty of Natural Science, Research environment Man & Biosphere Health (MABH). Kristianstad University, Faculty of Natural Science, Avdelningen för miljö- och biovetenskap.
    Olofsson, Patrik
    Heberg, Sweden.
    Strandberg, Roine
    Lund University.
    Hypotheses and tracking results about the longest migration: the case of the arctic tern2019In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758Article in journal (Refereed)
    Abstract [en]

    The arctic tern Sterna paradisaea completes the longest known annual return migration on Earth, traveling between breeding sites in the northern arctic and temperate regions and survival/molt areas in the Antarctic pack‐ice zone. Salomonsen (1967, Biologiske Meddelelser, Copenhagen Danske Videnskabernes Selskab24, 1) put forward a hypothetical comprehensive interpretation of this global migration pattern, suggesting food distribution, wind patterns, sea ice distribution, and molt habits as key ecological and evolutionary determinants. We used light‐level geolocators to record 12 annual journeys by eight individuals of arctic terns breeding in the Baltic Sea. Migration cycles were evaluated in light of Salomonsen's hypotheses and compared with results from geolocator studies of arctic tern populations from Greenland, Netherlands, and Alaska. The Baltic terns completed a 50,000 km annual migration circuit, exploiting ocean regions of high productivity in the North Atlantic, Benguela Current, and the Indian Ocean between southern Africa and Australia (sometimes including the Tasman Sea). They arrived about 1 November in the Antarctic zone at far easterly longitudes (in one case even at the Ross Sea) subsequently moving westward across 120–220 degrees of longitude toward the Weddell Sea region. They departed from here in mid‐March on a fast spring migration up the Atlantic Ocean. The geolocator data revealed unexpected segregation in time and space between tern populations in the same flyway. Terns from the Baltic and Netherlands traveled earlier and to significantly more easterly longitudes in the Indian Ocean and Antarctic zone than terns from Greenland. We suggest an adaptive explanation for this pattern. The global migration system of the arctic tern offers an extraordinary possibility to understand adaptive values and constraints in complex pelagic life cycles, as determined by environmental conditions (marine productivity, wind patterns, low‐pressure trajectories, pack‐ice distribution), inherent factors (flight performance, molt, flocking), and effects of predation/piracy and competition.

  • 2.
    Grönroos, Johanna
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Strandberg, Roine
    Lunds universitet.
    Olofsson, Patrik
    Alerstam, Thomas
    Lunds universitet.
    Klaassen, Raymond
    Skånska tärnors flyttning - ett forskningsprojekt2016In: Anser, ISSN 0347-9595, no 1, p. 20-26Article in journal (Other (popular science, discussion, etc.))
  • 3.
    Johanna, Grönroos
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Alerstam, Thomas
    Lunds universitet.
    Green, Martin
    Lunds universitet.
    Orientation of shorebirds in relation to wind: both drift and compensation in the same region2013In: Journal of Ornithology, ISSN 2193-7192, E-ISSN 2193-7206, Vol. 154, p. 385-392Article in journal (Refereed)
    Abstract [en]

    Migratorymovements in air or water are strongly affected by wind and ocean currents and an animal which does not compensate for lateral flow will be drifted from its intended direction of movement. We investigated whether arctic shorebirds during autumn migration in the region of South Sweden and the southern Baltic Sea compensate for wind drift or allow themselves to be drifted when approaching a known goal area under different circumstances (over sea, over land, at low and high altitude) using two different approaches, visual telescope observations and tracking radar. The shorebirds showed clearly different responses to crosswinds along this short section (\200 km) of the migratory journey, from almost full drift when departing over the sea, followed by partial drift and almost full compensation at higher altitudes over land during later stages. Our study demonstrates that shorebirds are also remarkably variable in their response to crosswinds during short sections of their migratory journey. The recorded initial drift close to departure is probably not adaptive but rather a result of constraints in the capacity of the birds to compensate in some situations, e.g. in low-altitude climbing flight over the sea. We found no difference in orientation response to wind between adult and juvenile birds. This study indicates, in addition to adaptive orientation responses to wind, the importance of the nonadaptive wind drift that contributes to increasing the variability of drift/compensation behaviour between places that are separated by only short distances, depending on the local topographic and environmental conditions.

  • 4.
    Johanna, Grönroos
    et al.
    Lunds universitet.
    Green, Martin
    Lunds universitet.
    Alerstam, Thomas
    Lunds universitet.
    To fly or not to fly depending on winds: shorebird migration in different seasonal wind regimes2012In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 83, no 6, p. 1449-1457Article in journal (Refereed)
    Abstract [en]

    Migratory birds are predicted to adapt their departure to wind, changing their threshold of departure and selectivity of the most favourable winds in relation to the mean, scatter and skewness of the wind regime. The optimal departure behaviour depends also on the importance of time and energy minimization during migration and on the ratio of cost of flight to cost of resting and waiting for more favourable winds. We compared departure and flight activity of shorebirds migrating in contrasting wind regimes during autumn (high probability of wind resistance) and spring (high probability of wind assistance) in southern Scandinavia, using data obtained by radiotelemetry, radar tracking and visual observations. The shorebirds changed their threshold for departure in relation to wind between the two seasons, flying almost exclusively with wind assistance in spring but regularly with wind resistance during autumn. The degree of wind selectivity in relation to the distributions of available wind effects was similar during autumn and spring indicating that reducing time and energy costs for migration was important during both seasons. These results demonstrate that migratory birds change departure behaviour in relation to the prevailing wind regime. It remains unknown whether they change behaviour not only seasonally but also in different zones along the migration route and whether they respond to differences not only in mean wind conditions but also in scatter and skewness between wind regimes. Our study indicates the possible existence of an adaptive flexibility in responses to wind regimes among migratory birds. (c) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

  • 5.
    Johanna, Grönroos
    et al.
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Gunnarsson, Gunnar
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Digitaliserade kursintroduktioner2017In: Högskolepedagogisk debatt, ISSN 2000-9216, no 2, p. 18-20Article in journal (Other (popular science, discussion, etc.))
  • 6.
    Johanna, Grönroos
    et al.
    Lunds universitet.
    Muheim, Rachel
    Lunds universitet.
    Akesson, Susanne
    Lunds universitet.
    Orientation and autumn migration routes of juvenile sharp- tailed sandpipers at a staging site in Alaska2010In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 213, no 11, p. 1829-1835Article in journal (Refereed)
    Abstract [en]

    Arctic waders are well known for their impressive long-distance migrations between their high northerly breeding grounds and wintering areas in the Southern hemisphere. Performing such long migrations requires precise orientation mechanisms. We conducted orientation cage experiments with juvenile sharp-tailed sandpipers (Calidris acuminata) to investigate what cues they rely on when departing from Alaska on their long autumn migration flights across the Pacific Ocean to Australasia, and which possible migration routes they could use. Experiments were performed under natural clear skies, total overcast conditions and in manipulated magnetic fields at a staging site in Alaska. Under clear skies the juvenile sharp-tailed sandpipers oriented towards SSE, which coincides well with reported sun compass directions from their breeding grounds in Siberia towards Alaska and could reflect their true migratory direction towards Australasia assuming that they change direction towards SW somewhere along the route. Under overcast skies the sandpipers showed a mean direction towards SW which would lead them to Australasia, if they followed a sun compass route. However, because of unfavourable weather conditions (headwinds) associated with overcast conditions, these south-westerly directions could also reflect local movements. The juvenile sharp-tailed sandpipers responded clearly to the manipulated magnetic field under overcast skies, suggesting the use of a magnetic compass for selecting their courses.

  • 7.
    Strandberg, Roine
    et al.
    Lunds universitet.
    Olofsson, Patrik
    Johanna, Grönroos
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Man & Biosphere Health (MABH).
    Alerstam, Thomas
    Lunds universitet.
    Klaassen, Raymond
    Årsrapport för tärnprojektet 20132013In: Spoven, ISSN 1103-0917, no 4, p. 39-41Article in journal (Other (popular science, discussion, etc.))
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