Sunday, August 12, 2012

Swainson's Hawk

On Saturday, 11 August 2012, Gene Bauer and I birded at Circle Lake in Rice County, Minnesota. We were delighted to find a Swainson's Hawk circling above the east shore of the lake. The raptor then flew off towards the north. I took the top photo that clearly shows the proper field marks for an adult Swainson's Hawk: dark chest, black flight feathers, and a somewhat pointed wing silhouette.
The second photo is of a bird found in eastern South Dakota several years ago. This bird breeds primarily in the Great Plains of the United States and Canada. In summer they are occasionally found along the western and southern borders of Minnesota. Swainson's Hawks are prairie birds. When breeding, although feeding their young rodents, rabbits, and reptiles, this hawk consumes almost only grasshoppers! Perhaps not coincidentally, after breeding, flocks of Swainson's Hawks begin a 10,000-kilometer migration to the Argentine pampas. Each fall, nearly a half-million individual hawks have been counted as they migrate over Mexico and Central America. Swainson's Hawk populations are declining. Radio tagging studies suggest that this decline is due to collateral pesticide poisoning in Argentina (Bechard et al. 2010).
I took this last photo near Aberdeen, South Dakota. This Swainson's Hawk is carrying a Tiger Salamander. None of my sources mentions amphibians in the lists of this hawk's prey items. Swainson's Hawks, despite their fondness for grasshoppers, must be opportunists when it comes to what they eat.

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