At Western University (Canada), I used a climatic wind tunnel built for birds to mimic non-stop migratory flights in a captive environment. I also took advantage of an automated radio telemetry array - the Motus Wildlife Tracking - to track large-scale migratory movements. I used two species of American migratory songbirds, the Blackpoll Warbler and the Yellow-rumped Warbler (Setophaga coronata coronata). Below, I present the work performed and results achieved for each of three main research objectives.
1. Study of the effects of endurance flight on circulating ghrelin and contents of ghrelin in the stomach
In a laboratory experiment, I flew birds in the wind tunnel for different durations (0.5 to 6 hours) and measured circulating levels of ghrelin at the end of each test. To measure the effects of endurance exercise on ghrelin regardless of the effects of fasting, I then used the same birds to perform a fasting non-exercising test for the same duration as they previously flew. I collected stomach tissue and measured ghrelin contents in a subset of birds. Data analysis is in progress.
2. Study of how ghrelin regulates fuel metabolism during flights
In a laboratory experiment, I injected birds with ghrelin, flew them for different durations (0.5 to 4 hour) in the wind tunnel and measured circulating levels of a number of key metabolites to determine what nutrients the bird was using to fuel its flight. I measured triglycerides, as an indicator of fat accumulation, and β-hydroxybutyrate, fatty acids and glycerol as indicators of fat mobilization. I also measured uric acid (product of protein metabolism), and glucose. Laboratory metabolite analysis is completed. Data analysis is in progress.
3. Study of how ghrelin affects migratory behavior
In a field experiment, I caught migrating birds at a spring stopover site and radio-tracked their movements following ghrelin administration and release. I measured the effects of ghrelin manipulation on stopover duration, departure decisions and post-departure migratory behavior. Results of this study show that on the day of release birds treated with ghrelin advanced departure from the field site – the Old Cut Research station (Ontario, Canada), indicating that ghrelin affects departure decisions. Ghrelin manipulation did not affect stopover duration, departure time of the day, flight trajectories or overall post-departure migratory behaviour. This confirmed that our approach to ghrelin administration (single acute peripheral injection) does not produce long-term effects. The link between circulating ghrelin and decision-making in free-living birds suggests an important role of peripheral metabolic hormones in the control of bird migration and charts new horizons in the study of migration physiology.
In a laboratory experiment, I injected birds with ghrelin and used video cameras and infrared lights to monitor their behavior in cage for 3 days. I measured the effects of ghrelin manipulation on diurnal and nocturnal locomotor activity and feeding behaviour. I repeated this experiment during migratory and non-migratory seasons to investigate potential seasonal differences in ghrelin’s functions. Furthermore, I conducted a laboratory experiment to test the duration of ghrelin increase in blood upon experimental ghrelin administration. Data analysis is in progress.
The first scientific manuscript generated by this project, entitled “Experimental ghrelin administration affects migratory behaviour in a songbird” is currently under review in the journal Hormones and Behavior. Despite difficulties in disseminating research due to the outbreak of the COVID-19 pandemic, I worked to promote my work through oral presentations and fruitful discussions with peers, collaborators, students and the public. I presented my research at the event “Women in Ornithology” organized by CISO (Centro Italiano Studi Ornitologici) as part of the initiatives celebrating The International Day of Women and Girls in Science promoted by the United Nations. This event, which targeted the general audience and researchers, was broadcasted live from the CISO Facebook page. My presentation is available to everyone at
https://ciso-coi.it/en/attivita/le-donne-nellornitologia/(si apre in una nuova finestra). I will also present the results generated by this project at three scientific conferences: the joint virtual meeting of the American Ornithological Society (AOS) and the Society of Canadian Ornithologists (SCO-SOC) in 2021, the International Symposium on Avian Endocrinology, Edinburgh, Scotland UK (ISAE) in 2022 and the Congress of the European Ornithologists’ Union, University of Giessen, Germany (EOU) in 2022.
