Abstract
Nectar exploitation by European birds mainly refers to passerines feeding on exotic plants, although some recent studies described nectar-feeding by trans-Saharan passerines on local plants. We examined which birds and plants are involved in nectar consumption and investigated the consequences of nectar use on plasma blood glucose concentrations during spring migration at a stopover site in the central Mediterranean. We recorded 12 opportunistic nectar-feeding species, with Sylvia warblers in particular showing a marked nectarivory, and 6 plants used by birds, no one of which shows typical “bird flowers” features. Moreover, we demonstrated that nectar uptake led to an increase in plasma glucose concentrations and that nectar was drunk not only by birds in poor physical condition. The nectar consumption is fully in accordance with time-minimising migration models, allowing birds to obtain water and energy at stopover sites in a short time: nectar is easy to find and quick to digest.
Zusammenfassung
Nektarkonsum durch europäische Singvögel wurde bisher vornehmlich an exotischen Pflanzen beobachtet. Jüngere Studien beschreiben aber auch Nektarkonsum durch trans-Sahar Zugvögel an einheimischen Pflanzen. In dieser Studie untersuchten wir während des Frühlingszuges an einem Rastplatz im zentralen Mittelmeerraum, welche Vogelarten welche Pflanzen für den Nektarkonsum nutzen, und welche Auswirkungen die Nektaraufnahme auf die Plasmakonzentration der Glukose hat. 12 Arten, insbesondere Grasmücken, tranken Nektar an insgesamt sechs Pflanzenarten, von denen keine die typischen Merkmale der Ornithophilie zeigte. Die Nektaraufnahme führte zu einem Anstieg der Plasmaglukosekonzentration und wurde vor allem von Vögeln in schlechter körperlicher Verfassung genutzt. Nektar ist eine Energiequelle mit vielen Vorteilen: sie ist schnell zu finden, rasch aufzunehmen und leicht zu verdauen. Dieser Vorteil, Wasser und Energie in kurzer Zeit aufzunehmen, reduziert die Zeit, die Zugvögel an einem Rastplatz verbringen müssen und unterstützt das Zeit-Minimierungsmodell.
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Acknowledgments
We are extremely grateful to Andrea Ferri and all other ringers who participated in the field activities at Ventotene ringing station. We thank Carlo Catoni and Diego Rubolini for important and useful suggestions and Simona Imperio for her enthusiastic and constructive discussions during the preparation of the manuscript. We also thank Fabrizio Bartolucci and Laura Cornara for the identification of Brassica montana and Anna McCann for the first proofreading. Result from Progetto Piccole Isole (ISPRA) paper no. 45.
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Communicated by C. G. Guglielmo.
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Cecere, J.G., Spina, F., Jenni-Eiermann, S. et al. Nectar: an energy drink used by European songbirds during spring migration. J Ornithol 152, 923–931 (2011). https://doi.org/10.1007/s10336-011-0675-4
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DOI: https://doi.org/10.1007/s10336-011-0675-4