Selon des recherches les outardes sont très sensible aux changements climatiques, 2 jours avant la tempête elles ressentent les variation barométrique et leur comportement changent. Voici un texte en anglais:
Reaction to Weather; Barometer, Wind, Precipitation, Temperature
Weather affects geese in a number of different ways. Dr. Cooper says that because geese have numerous air sacks in their body they have the ability to detect subtle barometric pressure changes. When fall storms approach geese stop feeding and begin to flock as much as two days before the storm. Heavy precipitation and strong winds may make it difficult for geese to fly. In extreme rain, snow or wind-chill geese may fly out only once late in the morning or not fly at all. If the temperature or wind-chill is below 10 degrees Giant Canadas often remain on the roost. If they fly in this weather they may actually lose more calories than they gain in feeding. They often feed heavily before or during the first few hours of a storm and when the weather lets up. Dr. Cooper's studies show that Giants can go 30 days without feeding and never leave the roost.
Migration
Geese begin to migrate in the fall when cold weather, strong winds and snow signal the onset of winter. They migrate only as far as they have to in order to find open water, available food, and temperature suitable to their body size. Because of their large body size Giant Canadas can withstand colder temperatures than their smaller relatives. They may not fly any farther south than the northern tier of the United States.
Donc elles se sont rassemblés avant le mauvais temps et sont partis avant que le mauvais temps arrive.
Nico
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