On migration, most passerine birds stop over along the way to rest and refuel. A network of hormones signals metabolic fuel availability to the brain in vertebrates, including the recently discovered gut-hormone ghrelin. Here, we show that ghrelin participates in the control of migratory behaviour during spring migration in a wild migratory passerine. We administered ghrelin to yellow-rumped warblers (Setophaga coronata coronata) caught during stopover and automatically radio-tracked their movements following release. Ghrelin rapidly induced birds to move away from the release site, indicating that the ghrelin system acts centrally to mediate stopover departure. The effects of the hormone treatment declined within hours following release and did not affect the overall rate of migration. These results provide experimental evidence for a pivotal role of ghrelin in the modulation of stopover decisions during migration, and offers insights into the regulatory functions of metabolic hormones in the dialogue between gut and brain in birds.

The study was a collaboration with Christopher G. Guglielmo, Scott A. MacDougall-Shackleton, and Yolanda E. Morbey of the Advanced Facility for Avian Research, University of Western Ontario, Canada, and Hiroyuki Kaiya of the National Cerebral and Cardiovascular Center Research Institute, Japan.

Funding was provided by the Marie Skłodowska-Curie Individual Global Fellowship 798739 GHRELMIGRA to Sara Lupi

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