Monday, August 18, 2014

Cooper’s Hawk 2

On Saturday, 16 Aug 2014, Erika and I heard a loud, strident, mewing high in the trees at the University of Minnesota Landscape Arboretum in Carver County, just west of Minneapolis. This large hawk was actually difficult to see among the branches. Note how much shorter the hawk’s outer tail feathers are than the central ones—a good field mark of the Cooper’s Hawk.  Other hawks have their tail feathers of about equal length.

Undoubtedly a first-year female—females are about one-third larger than males. The species shows the greatest reverse size dimorphism of any hawk (Curtis et al. 2006). This disparity makes life kind of tough for the males, who are submissive to the females. The males are about the right size to be a meal. Females make reassuring calls when they are willing to be approached males. Males do the nest building and provide almost all the food to the female and young (Allaboutbirds.org).

Cooper’s Hawk numbers appear to be increasing. Surveys indicate increases of 10% in Michigan and 12.3% in Wisconsin. Moreover, Cooper’s Hawks have become common in urban and suburban areas. Allaboutbirds.org writes that Rock Pigeons and Mourning Doves are often consumed. Some Arizona birds suffer from parasites acquired by eating doves (Allaboutbirds.org). In any event, the Cooper’s Hawks in our neighborhood seem to have consumed many of our local birds.

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