Regional and seasonal flight speeds of soaring migrants and the role of weather conditions at hourly and daily scales

By W. Vansteelant, Willem Bouten, R. Klaassen, B. Koks, A. Schlaich, J. V. Diermen, E. V. van Loon, J. Shamoun‐Baranes. 2015

119 citations recorded by the source corpus.

Given that soaring birds travel faster with supportive winds or in good thermal soaring conditions, we expect weather conditions en route of migration to explain commonly observed regional and seasonal patterns in the performance of soaring migrants. We used GPS-loggers to track 13 honey buzzards and four Montagu's harriers for two to six migrations each. We determined how tailwinds, crosswinds, boundary layer height (a proxy for thermal convection) and precipitation affected hourly speeds, daily distances and daily mean speeds with linear regression models. Honey buzzards mostly travel by soaring while Montagu's harriers supplement soaring with flapping. Therefore, we expect that performance of harriers will be less affected by weather than for buzzards. Weather conditions explained between 30 and 50% of variation in migration performance of both species. Tailwind had the largest effect on hourly speeds, daily mean speeds and daily travel distances. Honey buzzards travelled significantly faster and farther, and Montagu's harriers non-significantly faster, under better convective conditions. Honey buzzards travelled at slower speeds and shorter distances in crosswinds, whereas harriers maintained high speeds in crosswinds. Weather conditions varied between regions and seasons, and this variation accounted for nearly all regional and seasonal variation in flight performance. Hourly performance was higher than predicted at times when we suspect birds had switched to intermittent or continuous flapping flight, for example during sea-crossings. The daily travel distance of Montagu's harriers was determined to a significant extent by their daily travel time, which differed between regions, possibly also due to weather conditions. We conclude with the implications of our work for studies on migration phenology and we suggest an important role for high-resolution telemetry in understanding migratory behavior across entire migratory journeys.

Subfields: Ecology, Ecology, Evolution, Behavior and Systematics

View Paper: https://www.semanticscholar.org/paper/9fd14ce6c18fd3db6292c30bb9fbb5ddc449b7c6

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In Ecology

1. Stoyan Nikolov
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3. Martin Wikelski
4. Victoria Saravia
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6. E. Kret
7. B. Nolet
8. S. Oppel

In Ecology, Evolution, Behavior and Systematics

1. Martin Wikelski
2. S. Cooke
3. Frederic Bartumeus
4. A. Moles

Citations in the corpus

• Towards a new understanding of migration timing: slower spring than autumn migration in geese reflects different decision rules for stopover use and departure (2016, background): “GLMM test results indicate a significant difference of height above ground, but not ground speed between the seasons. et al. 2012, Vansteelant et al. 2015), indicating that environmental factors are perhaps in general more likely the drivers of migration timing strategies.”
• High juvenile mortality during migration in a declining population of a long-distance migratory raptor (2015, background): “…of autumn migration, their travel speed, measurements of body size taken at the time birds were tagged, or environmental variables that are known to affect the initiation of migration and migration route of soaring raptors (Shamoun-Baranes et al. 2006, Dodge et al. 2014, Vansteelant et al. 2015).”