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Discovery of the Eagle Migration

Out of the blue

On March 20 1992, Peter Sherrington and Des Allen were conducting a general bird survey in the Kananaskis Valley near Mount Lorette. Late in the morning Peter observed an adult Golden Eagle soaring high above the valley to the east of Mount Lorette. A short time after they saw two adults soaring over the mountain. These two birds were quickly joined by a third. All three moved off to the northwest, to be replaced a few minutes later by more birds moving from the southeast. By the end of the day Peter and Des had counted over 100 Golden Eagles migrating to the northwest. Two days later Peter led a group of amateur naturalists to the area to look for eagles and they were rewarded by seeing nearly 250 Golden Eagles flying from southeast to northwest in a single afternoon.

Until this time it was generally accepted that only relatively low numbers of Golden Eagles migrated, mainly through the Rocky Mountain Foothills, that most of the birds were immature and that they were not moving long distances. This model was now about to change.

The following fall observers spent 33 days studying the migration and recorded 2,672 raptors of which 2,043 were Golden Eagles. In the spring of 1993, 49 days of observation yielded 4,140 Golden Eagles, and the following fall yielded an astonishing 4,499 birds. By this time groups of observers had begun to find other sites at which eagles could be seen between the Crowsnest Pass and Jasper. In the fall of 1994 two groups counting at the Hay Meadow and Barrier Lake sites established that over 6,000 Golden Eagles passed south through the Front Ranges of the Alberta Rocky Mountains.

By the end of the fall 2003 migration, observers at the main Hay Meadow site (including one fall migration count conducted at Plateau Mountain 100 km to the southeast) had spent 1,775 site-days (17,208 hours) counting 96,974 migrant raptors of 18 species. Of this total 80,814 were Golden and 6,765 Bald Eagles.


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