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Arb Notes

February 7, 2008 at 6:31 pm
By Arb Naturalists

The fresh blanket of snow covering the Arb makes it a great time to look for signs of predation! If you dare to venture off the trails, the white backdrop emphasizes scatterings of feathers, fur, and blood that in other seasons are relatively difficult to spot. The following will help you to identify the signs left by three common predators in the Arb.

Sharp-shinned Hawk (Accipiter striatus) This relatively small bird of prey is the most common avian predator in the wooded parts of the Arb. Although more than 90% of its diet is small perching birds, sharp-shinned hawks opportunistically hunt small mammals and larger birds like woodpeckers. When looking for the signs of this predator, look for piles of feathers that were plucked from the animal before consumption. Given that sharp-shinned hawks often return to the same location to consume their kills, feathers of more than one bird can be found in a small area.
Cooper’s Hawk (Accipiter cooperii) Like sharp-shinned hawks, Cooper’s hawk is generally an opportunistic hunter that specializes on birds. Given its larger body size, Cooper’s hawk is able to take down larger prey, including blackbirds, grouse, squirrels and even sharp-shinned hawks! The best way to distinguish between signs left by sharp-shinned and Cooper’s hawks is to examine the size of the feathers scattered around the site of the kill (Cooper’s hawk kill-sites will generally be strewn with larger feathers). However, this method is far from perfect given that a large sharp-shinned hawk and a small Cooper’s hawk prey upon birds of similar sizes.
Long-tailed weasel (Mustela frenata) Weasels are known for their hunting prowess and are often able to kill prey that is equal to them in body size. Common prey in the Arb includes meadow-voles, pocket gophers and ground squirrels. Weasels are much sloppier predators than the Accipiters, often leaving behind intestines and other organs in addition to fur. Long-tailed weasels also have the curious habit of cashing prey for later consumption, which sometimes entails hanging half-eaten carcasses on twigs or thorns. Mmmmm!

- Your Student Naturalists are Amy Alstad ’09, Jeremy Hayward ’09, Lindsey Nietmann ’09, David Smith ’09 (off-campus), Hannah Specht ’09, John Vigeland ’09, and Mira Alecci ’11. Please contact any of us (or Arb Director, Nancy Braker) with questions or suggestions!

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