Ghrelin affects stopover decisions and food intake in a long-distance migrant.
Billions of birds migrate long distances to either reach breeding areas or to spend the winter at more benign places. On migration, most passerines frequently stop over to rest and replenish their fuel reserves. To date, we know little regarding how they decide that they are ready to continue their journey. What physiological signals tell a bird's brain that its fuel reserves are sufficient to resume migration? A network of hormones regulates food intake and body mass in vertebrates, including the recently discovered peptide hormone, ghrelin. Here, we show that ghrelin reflects body condition and influences migratory behavior of wild birds. We measured ghrelin levels of wild garden warblers (Sylvia borin) captured at a stopover site. Further, we manipulated blood concentrations of ghrelin to test its effects on food intake and migratory restlessness. We found that acylated ghrelin concentrations of garden warblers with larger fat scores were higher than those of birds without fat stores. Further, injections of unacylated ghrelin decreased food intake and increased migratory restlessness. These results represent experimental evidence that appetite-regulating hormones control migratory behavior. Our study lays a milestone in migration physiology because it provides the missing link between ecologically dependent factors such as condition and timing of migration. In addition, it offers insights in the regulation of the hormonal system controlling food intake and energy stores in vertebrates, whose disruption causes eating disorders and obesity.
Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, D-82319 Seewiesen, Germany.
Wolfgang
0000-0002-7553-5910
W
Goymann
Department of Life Sciences and Biotechnology, University of Ferrara, 44100 Ferrara, Italy.|Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, 1160 Vienna, Austria.
Sara
S
Lupi
Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
Hiroyuki
H
Kaiya
Swedish University of Agricultural Sciences, Department of Aquatic Resources, Marine Research Institute, 45330 Lysekil, Sweden.
Massimiliano
M
Cardinale
Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, 1160 Vienna, Austria; leofusani@gmail.com.|Department of Cognitive Biology, University of Vienna, 1090 Vienna, Austria.
Leonida
0000-0001-8900-796X
L
Fusani
D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001069:Appetite Regulation / Q000502:physiology*; D001823:Body Composition; D005247:Feeding Behavior / Q000502:physiology*; D054439:Ghrelin / Q000502:physiology*; D012621:Seasons; D020308:Songbirds / Q000502:physiology*
D054439:Ghrelin
bird migration; food intake; ghrelin; migratory restlessness; stopover