Date: Winter 2012-2913
It's early December in NY and today I pulled over to the side of a country rode because a cloud of Canadian geese caught my eye. There were over 300 flying in a large circle around a grove of trees, quite a distance high, in various, seemingly intentional formations. I watched them for at least 10 minutes--they must have made at least eleven revolutions. Could they have just been preparing for a long migration this late in the season? Or, could there have been something off in the magnetic field they rely on for migration?
Sandhill cranes often circle in that manner over thermals of rising warm air to gain altitude before moving on. I am not aware of Canada geese using thermals but its possible. It is very unlikely any navigation sense was awry.
Thanks for the question. I am not sure what the cause of geese's flight patterns is. I (personally) suspect that the geese were taking some sort of "rest break." Before concluding that there is something "off" regarding the magnetic field of Earth, I would check with the aviation industry and check into corrections for magnetic compasses. (Yes, the magnetic compasses in aircraft do drift during flight.)
Geese will fly high (to find the wind that is blowing in the direction they want to go) and circle until and whole crowd gathers to take off in the direction they want to go. If there was a magnetic anomaly strong enough to effect their migration, they would still be circling.
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Update: November 2011