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  • 1. Felton, Adam
    et al.
    Lindbladh, Matts
    Elmberg, Johan
    Felton, Annika M.
    Andersson, Erik
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Sekercioglu, Cagan H.
    Collingham, Yvonne
    Huntley, Brian
    Projecting impacts of anthropogenic climatic change on the bird communities of southern Swedish spruce monocultures: will the species poor get poorer?2014In: Ornis Fennica, ISSN 0030-5685, Vol. 91, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The potential impact of climatic change on bird species' distributions in Europe was recently modeled for several scenarios of projected late 21st century climate. The results indicate mean range shifts of hundreds of kilometres north for many of European bird species. Here we consider the implications from such distributional shifts for the bird communities of Norway spruce (Picea abies) monocultures in southern Sweden, a forest type likely to remain prevalent due to forestry, despite climate change. Our assessment led us to three key findings. First, the monocultures offer suitable habitat to only two bird species projected to extend their breeding distribution northwards into southern Sweden this century. Second, species richness was projected to decline overall, which would accentuate the depauperate nature of these stands. Third, all conifer-associated arboreal granivores and three of four conifer-associated arboreal insectivores were projected not to occur, reducing both the functional richness and functional redundancy. We discuss caveats related to our approach, including the potential for bioclimatic projections - used in this study - to be hampered by the artificial retention of dominant vegetation. We also discuss the implications of our results for avian biodiversity in what is today the most prevalent forest type in southern Sweden and in many other regions of Europe.

  • 2.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Gustin, Marco
    LIPU.
    Sorace, Alberto
    Instituto Superiore di Sanità.
    Compensatory bodily changes during moult in tree sparrows, Passer montanus, in Italy2004In: Ornis Fennica, ISSN 0030-5685, Vol. 81, no 2, p. 75-83Article in journal (Refereed)
    Abstract [en]

    To cope with fluctuating environments animals have evolved reversible phenotypic flexibility.Some birds demonstrate this phenomenon by changing mass and flight muscle according to changes in wing loading. During moult, birds suffer from reduced wing area because feathers are shed and replaced, resulting in a wing loading increase. Moult is rather well studied in birds, but the perspective of phenotypic flexibility has been neglected. Therefore,we tested predictions generated from experimental studies by collecting information about bodymass, flightmuscle size and fat stores from an Italian population of Tree Sparrows (Passer montanus) to investigate if they compensate physiologically for the wing area reductions they suffer from during moult. Our results did not corroborate predictions based on experimental studies; that is, the Tree Sparrows did not reduce body mass and increase in flight muscle size as a response to wing area reductions during midmoult. Instead, body mass increased throughout moult, flight muscle size did not change, and fat stores decreased asmoult progressed. To further investigate compensatory changes, we analysed bodily differences in midmoult between birds differing in moult gap size. Again, contrary to predictions from experimental studies, birds having larger moult gaps were found to have higher body mass. These birds were also found to keep the ratio between flight muscle size and body mass constant over the day whereas birds with small moult gaps reduced this ratio over the day. Birds with large moult gaps ere also found to store less fat than birdswith small gaps. Physiological constraints may help to explain these results and underlying reasons for the observed variation in bodily regulation in birds are discussed.

  • 3.
    Lind, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jöngren, Fredrik
    Stockholm University, Faculty of Science, Department of Zoology.
    Nilsson, Jenny
    Stockholm University, Faculty of Science, Department of Zoology.
    Schönberg Alm, David
    Stockholm University, Faculty of Science, Department of Zoology.
    Strandmark, Alma
    Stockholm University, Faculty of Science, Department of Zoology.
    Information, predation risk and foraging decisions during mobbing in great tits, Parus major2005In: Ornis Fennica, ISSN 0030-5685, Vol. 82, p. 89-96Article in journal (Refereed)
    Abstract [en]

    Tomaximise survival during foraging animalsmust decide when and for how long foraging should be interrupted in order to avoid predators. Previous experiments have shown that birds that hear other individuals’alarm calls resume feeding later than those that see a flying predator.However, the responses of prey animals to enemies are highly context-dependent. We therefore investigated how birds respond to a threat less serious than a flying hawk depending on different amount of information about the predator. We used Great Tits dyadswhere one individual saw a perchedmodel predator (sender), whereas the other individual could only hear the conspecific’s mobbing calls (receiver). The sender responded appropriately as shown by comparing their responses to how they responded to a control.We also found that while senders were exposed to the predator, receivers became more wary and reduced their activity level. However, despite the receivers having less information about predation risk they still did not prolong the time they took to resume foraging. Hence, once the mobbing ceased (and consequently the transmission of information about the predator stopped) therewas no effect of only having second-hand information. This also shows that receiver’s rely upon the sender’smobbing calls suggesting that mobbing calls may act as honest signals of the prevailing predation risk. In conclusion, our results support the view that responses of prey to predators are highly context-dependent and that birds’ anti-predator responses are a result of an interaction between the amount of information and the level of the threat.

  • 4.
    Lomas Vega, Marta
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Copenhagen, Denmark.
    Thorup, Kasper
    Local weather, food resources and breeding stage influence Thrush Nightingale movement2018In: Ornis Fennica, ISSN 0030-5685, Vol. 95, no 4, p. 151-159Article in journal (Refereed)
    Abstract [en]

    Insectivorous migrants breeding at northern latitudes often time the breeding period with the seasonal peak of food resources. Whether this general pattern transfers to movement behaviour during the breeding season requires detailed study from a local perspective. We investigated fine-scale environmental correlates of movements by six actively-breeding adult Thrush Nightingales (Luscinia luscinia) at a breeding site in Denmark, using radio tracking and multiple regression models. Overall, the chick-rearing period coincided with the peak of vegetation greenness at the site. Adults flew further from nesting areas during stable weather and as vegetation greenness decreased. Adults were more active at higher environmental temperatures and when fledglings were older but still dependent on adults. These changes in local movements likely reflect adjustments to chick developmental needs and to specific local environmental conditions, including resource availability.

  • 5.
    Nyström, Jesper
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Ekenstedt, Johan
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Thulin, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Golden Eagles on the Swedish mountain tundra - diet and breeding success in relation to prey fluctuations2006In: Ornis Fennica, ISSN 0030-5685, Vol. 83, no 4, p. 145-152Article in journal (Refereed)
    Abstract [en]

    We studied the diet and the relationship between prey density fluctuations and breeding success of a Golden Eagle (Aquila chrysaetos) population on the mountain tundra region of northern Sweden. We used a new PCR based method to analyse the DNA in bone fragments from Golden Eagle prey remains. This allowed us to accurately identify the Ptarmigan species that the bone fragments originated from, and hence, establish the proportions of Ptarmigan species in the eagle's diet. We could conclude that Ptarmigan species (Lagopus spp.) are the most important prey category for this Golden Eagle population (63% of all identified prey), and that Willow Ptarmigan (L. lagopus) occurred more frequently in the diet than Rock Ptarmigan (L. mutus) did (Willow Ptarmigan 38%, Rock Ptarmigan 25%). Other important prey included reindeer (Rang fer tarandus), mountain hare (Lepus timidus) and microtine rodents. The Golden Eagles managed to maintain a relatively broad food niche, despite an environment with low prey diversity. Microtine rodents, hare and Ptarmigan populations showed similar population fluctuations in the study area. The breeding success of the Golden Eagles showed a strong relationship to the yearly density index of the most important prey category, the Ptarmigan species.

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