Weather radar is a practical but underused tool to help predict landbird migration, according to new studies that used Doppler weather surveillance to monitor how weather and geography affect landbird migration patterns along the north and south shores of the St. Lawrence estuary.

Researchers studied a fall migration season and found that the St. Lawrence estuary acts as a geographical cue and barrier for some landbirds, which helps shape migration patterns down the continent. In general, they found that extensive and strong winds and/or rain dramatically reduced the probability of a strong migration event. In addition, landbirds on opposite sides of the estuary displayed different migration behaviour in wind and precipitation events.

Landbirds on the north coast were more likely to correct their flight paths after being displaced by wind. This compensation ensured that higher concentrations of landbirds were following the same southwest migration pathway on the north coastline. It appears that these efforts were intended to avoid crossing over the estuary which, although relatively narrow, may represent an unwanted detour requiring energy expenditure to return to the migration route.

On the south coast, landbirds had more scattered flight directions and were more likely to drift due to winds. This may explain why wind was more likely to suppress strong migration activity on the north coast, compared to the south.

Scientists say this data can help predict the intensity of landbird migration and assist decisions in a variety of contexts such as environmental assessments (i.e., wind-power developments), human safety (i.e., reduce likelihood of bird and aircraft collisions), and bird conservation (i.e., reduce building collisions, one of the leading causes of migratory bird deaths, and locate and protect important migration stopover areas).

Publications:

Gagnon, F., J. Ibarzabal, J.-P.L. Savard, P. Vaillancourt, M. Bélisle and C.M. Francis. 2011. Weather effects on nocturnal migration of passerines on opposite shores of the St. Lawrence estuary. The Auk 128(1):99-112.

Gagnon, F., J. Ibarzabal, J.-P.L. Savard, M. Bélisle and P. Vaillancourt. 2011. Autumnal patterns of nocturnal passerine migration in the St. Lawrence estuary region, Quebec, Canada: a weather radar study. Canadian Journal of Zoology 89:31-46.

Contact: Dr. Jean-Pierre Savard, 418-648-3500