Fascinating Snow Geese

Snow Geese are endlessly fascinating. At high tide they move en masse to the fields adjacent to the St. Lawrence. Numbers swell as small groups of two or three glide overhead. Suddenly, they burst into the air, swirling in unison only to land in the next open area. When you watch long enough you begin to sense this explosive moment. I think a critical mass is reached and the geese erupt to release the pressure. I'd like to hear other explanations of this behaviour please.

I love spring time when each tree shows it individual shade of greenery. On April 12, during our last visit, grays and brown dominated a cool landscape.

Canon 7D, 70-200 f/4L lens adjusted to 110 mm, f/7.1, 1/2000s, ISO 400, focus set on Auto-Servo (continuous focus for following moving objects)

Park rangers estimated 42000 snow geese present on May 11. Below, you can see some of them feeding offshore along the tidal flats.