Experimental ghrelin administration affects migratory behaviour in a songbird

Authors: Sara Lupi, Yolanda E. Morbey, Scott A. MacDougall-Shackleton, Hiroyuki Kaiya, Leonida Fusani, and Christopher G. Guglielmo

Year: 2022

Publication: Hormones and Behavior

Publication Link: https://doi.org/10.1016/j.yhbeh.2022.105139

Keywords: Ghrelin, Bird migration, Stopover, Migratory behaviour, Radio-tracking, Yellow-rumped warbler, Locomotor activity, Hormone, Departure decision, Gut-brain

Abstract: Twice a year, billions of birds take on drastic physiological and behavioural changes to migrate between breeding
and wintering areas. On migration, most passerine birds regularly stop over along the way to rest and refuel.
Endogenous energy stores are not only the indispensable fuel to complete long distance flights, but are also
important peripheral signals that once integrated in the brain modulate crucial behavioural decisions, such as the
decision to resume migration after a stopover. 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 takes
part in the control of migratory behaviour during spring migration in a wild migratory passerine. We manipulated
blood concentrations of ghrelin of 53 yellow-rumped warblers (Setophaga coronata coronata) caught during
stopover and automatically radio-tracked their migratory behaviour following release. We found that injections
of acylated and unacylated ghrelin rapidly induced movements away from the release site, indicating that the
ghrelin system acts centrally to mediate stopover departure decisions. The effects of the hormone manipulation
declined within 8 h 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 behavioural decisions during migration.
In addition, this study offers insights into the regulatory functions of metabolic hormones in the dialogue between
gut and brain in birds.

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