11-12-13 Bird Field Note

11-12-13 Bird Field Note

November 12, 2013

Eric Rasmussen and Kate Stone describe a rebuilt bald eagle nest, and the final stretch of fall raptor migration counts.

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Bird Field Note Kate Stone, Eric Rasmussen

The loss of cottonwood leaves reveals major additions to the artificial Bald Eagle nesting platform near the Guest House (left). After damage in a May wind storm, the old nest tree lost its high, large branches that could support a new nest (right). In Montana, we know of only two other instances when Bald Eagles used an artificial platform. A pair of eagles used a platform at Lee Metcalf National Wildlife Refuge for several years, but the nest tree blew over in 2012. A Bald Eagle usurped an Osprey platform in the Big Hole Valley in 2010.

Raptor numbers dwindled to 21 as we entered the final stretch of fall migration. Mostly cloudy skies persisted all week, accompanied by valley rain and snow. Eagles, red-tailed and rough-legged hawks continued their late season migration. Last year these raptors came through in large numbers near the end of our count, which ended on November 12th. If the current numbers hold steady we will stick to this scheduled end date to ensure that we don’t miss any late migrants.

Dark rough-legged hawks (top) have a dark body and wing linings, compared to the distinct belly band and carpal patches on the wing of a light morph (bottom).

A northern harrier exhibits the classic ‘T’ shape with long, slender wings and tail.

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