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

Introduction

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.

Project Aim

The overall aim of this project is to reveal constraints and the behavioural and physiological adaptations that have evolved to overcome them, thus making the extreme performances of migratory birds possible.

Methodology

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
• 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.

Unexpected Discoveries

In particular, I have together with colleagues 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?

Proposed Changes to Understanding

By launching an extensive 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:

1. Disentangling the causes and consequences of birds’ altitudinal behaviour
2. Investigating the flexibility, timing, and duration of migratory flights (if birds only use diurnal or nocturnal flights, if they prolong flights to last both day and night, or even fly nonstop between wintering and breeding grounds)
3. Analyzing the costs and consequences of these seemingly extreme behaviours.