Melissa Bowlin and Martin Wikelski investigated how much energy Swainson’s thrushes (see picture on left) are using at different wind velocities by having the bird fly in a wind chamber (see picture to the right). Below, Melissa describes their main results:

In an article recently published in the scientific journal PLoS ONE, Martin Wikelski and I showed that small migratory birds use more energy when storms are developing and when winds are high than when it is clear and calm. Since global climate change may affect the frequency and severity of storms and winds, climate change could have large impacts on the amount of energy these birds have to use during flight. Most small birds barely carry enough fat to fuel their flights over ecological barriers such as the Gulf of Mexico and the Mediterranean Sea. If climate change increases the number of times that birds encounter bad weather while flying over these barriers, more birds will run out of energy and die while making these crossings.

While this would be disastrous for those individuals, the species themselves would almost certainly persist—individuals could pack on more fat before leaving (although we showed that carrying more weight can increase the cost of flight), or the species may evolve energy-saving features such as pointed wings (which we showed decrease the cost of flight). Still, many researchers think that the population sizes of some migratory bird species are determined by how many individuals survive during migration, so a change in the numbers of birds that die during migration may have unforeseen consequences.

Melissa Bowlin, postdoc at the University of Montana, Missoula, Montana, USA

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