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Earth Notes: Hawks in Vultures' Clothing

Very rare 20 years ago, the zone-tail is now a commonly seen bird in the Grand Canyon as its range has expanded northwards.
Robb Hannawacker
National Park Service
Very rare 20 years ago, the zone-tail is now a commonly seen bird in the Grand Canyon as its range has expanded northwards.

Zone-tailed hawks are large soaring hawks native to the southwestern United States. Unlike their nearest relatives, when soaring they display slightly V-shaped wing postures and rock from side to side. That’s the same way turkey vultures soar. And like turkey vultures, zone-tailed hawks have dark bodies and two-toned under-wings.

Why do zone-tails seem to mimic turkey vultures and even frequently soar among them? The answer is thought to be a hunting advantage. A dove, lizard or chipmunk on the ground might ignore the presence of a harmless turkey vulture, which only eats carrion, soaring overhead, whereas the silhouette of a hawk normally sends small creatures scurrying for shelter. So, the zone-tailed hawk’s similarity to turkey vultures may allow them to sneak up on prey. It’s a variation on the “wolf in sheep’s clothing” strategy!

This is a compelling case of what’s known as “aggressive mimicry,” where a predator pretends to be harmless, as opposed to the more common “protective mimicry,” in which a mimic avoids being eaten by its resemblance to a dangerous or distasteful creature.

Zone-tailed hawks have been observed soaring in a group of turkey vultures, then suddenly plummeting earthward in a predatory dive. It’s easy to see how this “hawk in vulture’s clothing” approach helps the zone-tailed hawk capture unsuspecting prey on the ground. It’s a fascinating form of mimicry found in our natural world.

This Earth Note was written by Steve Schwartz and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.

Steve first came to Flagstaff in the late 1970s to study at Northern Arizona University, where he obtained a master’s degree in biology, and he feels fortunate to have been able to call Flagstaff home for over thirty years. Recently retired after a long career in healthcare administration, his retirement allows him to spend large amounts of time exploring the rich diversity of the Colorado Plateau. Steve considers himself a lifelong learner and he can often be found exploring with his two dogs, Quinn and Rosie, indulging his passions for biology and the natural world.
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