DOING THE IMPOSSIBLE - adaptive behaviour in migratory birds to overcome physiological and environmental constraints

Project Information

MigPerform

Grant agreement ID: 101078349

DOI

10.3030/101078349

EC signature date 12 December 2022

Start date 1 September 2023

End date 31 August 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 499 921,00

EU contribution

€ 1 499 921,00

Coordinated by

LUNDS UNIVERSITET
Sweden

Periodic Reporting for period 1 - MigPerform (DOING THE IMPOSSIBLE - adaptive behaviour in migratory birds to overcome physiological and environmental constraints)

Reporting period: 2023-09-01 to 2026-02-28

Summary of the context and overall objectives of the project

Advances in tracking technology during the last decade have shown that migratory birds have the capacity to fly longer and faster than we previously thought was possible. Yet, we do not know how birds perform these seemingly impossible travels as it previously only was possible to record spatiotemporal patterns. A new tracking technology now allow us to record key aspects of migratory behaviour and physiology of birds throughout their migration. With this new technology, we learn not only where birds go, but also how they get there. This gives us the possibility to in detail study complete journeys and strategies, allowing us to change our understanding of how birds succeed with their seemingly impossible migratory journeys.

The overall aim of this project is to reveal constraints and the behavioural and physiological adaptations that has evolved to overcome them, thus making the extreme performances of migratory birds possible. This goal will be met by using novel tracking devices, multisensor data loggers, that in addition to spatiotemporal patterns also record behaviour, including flight altitudes, temperature and detailed timing of flights and stopovers during the entire migration cycle. The few multisensor tracking studies carried out to date have provided hints of stunning new insights, and seriously challenged previously assumed limits on peak flight altitudes, in-flight changes of altitudes, and duration of individual flights. In particular, the PI has together with colleagues previously discovered a totally unexpected altitudinal behaviour: some bird species change their flight altitude between night and day, and fly at extremely high altitudes during the day (up to 6000-8000 m). But what makes a migratory bird fly as high as Mount Everest, even when there are no mountains to cross?

By a multisensor data logging programme, combined with wind tunnel experiments and field studies, the proposed project will change our understanding of the possibilities and limitations of bird migration. This will be done by disentangling the causes and consequences of bird’s altitudinal behaviour, the flexibility, timing and duration of migratory flights, and the costs and consequences of these behaviours.
This is first and foremost a leading-edge project in basic research. Yet, migration is an important part of the life cycle of many organisms, not least birds, and for humans one of the most fascinating events in nature. Today, many long-distance migratory birds are declining and a better understanding of animal migration in general is necessary to predict how global change may affect migratory species.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In order to understand how birds use adaptive behaviours to overcome physiological and environmental constraints during migration, we first need to disentangle how birds perform their migration. This is done by tracking the behaviour of birds throughout the full annual cycle using different types of tracking devices. Hence, an extensive tracking programme has been initiated. For most species/studies data collection is still ongoing, but some first findings are already published.

As a first step to disentangle how constrained birds are in their migratory flight plan (flight hours, timing and duration of flights) we tracked the behaviour of the red-backed shrikes throughout the full annual cycle. It has been known for decades that migratory songbirds have an internal genetic program that controls the timing and extent of migratory flight activity. However, in this study annual activity patterns unexpectedly revealed that the nocturnal migratory flights of the shrikes were organized in a highly structured way with flights aggregated into segments, showing low variability and thus high consistency between individuals. Potentially, this would mean that the internal/genetic program for control of bird migration is much more dynamic and complex than hereto assumed.
To further understand how migratory birds divide their flights between nocturnal and diurnal flights we tracked the behaviour of snow buntings and showed that for their longer migratory flights they predominantly use nocturnal flights, but they use daytime movements for more nomadic movements. In addition to this we could show that this species that breeds in polar day conditions keep their 24-h diel rhythm throughout the breeding period.

A series of experimental projects in the AFAR wind tunnel facilities at Western University, Ontario, Canada have been initiated to further reveal the cause of high altitudinal flights during daytime, and the first preliminary results are expected winter 2026.

To further underline the knowledge gaps related to altitudinal use of aerial species, the PI has written a review paper together with colleagues from Sweden, the U.S. and the Netherlands. In this review, environmental conditions and biological interactions influencing where animals occur in the airspace throughout their life cycles were identified and an ecological framework to advance understanding of how the airspace shape aerial habitat niches was outlined.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

One of the main objectives in this action is to understand why migratory birds increase several kilometres in altitude when prolonging nocturnal flights into daytime. Three main hypotheses have been suggested to explain this, avoidance of diurnal predators, increased visual range and that birds climb to these high and very cold altitudes to counteract heating from solar radiation during daytime. By revealing the cause of the behaviour, I anticipate that we will not only understand why birds fly as high as our highest mountains even though there are no mountain to pass but also gain understanding on how birds manage to use sustained flapping flight over longer periods. If thermoregulation plays out as a key factor for flight performance in birds, our knowledge about adaptations and constraints to bird migration will completely change. Additionally, this behaviour might explain the puzzling fact that vast majority of migrants predominantly fly during the night even though they otherwise only are strictly diurnal.