May 2022
Bird of the Month
by
Ryan Crouse

Zone-Tailed Hawk

Mid-April is a time of transition. The weather is sporadic as the region tries to decide whether it is still winter. Plants and insects are waiting for their cues to start becoming more active. Along those same lines, the bird population is in a state of flux, with wintering species heading north as summer migrants begin to trickle in. As I was leading a bird-walk yesterday we spotted some of these summer species. Among them were two beautiful zone-tailed hawks soaring together. These were the first of the season for me, and they’re always a welcome sight, among my favorites to observe in the field.

For me there are several traits of the zone-tailed hawk that make it stand out from other raptors. I should back up, though.

John West

Earlier in the morning we’d spotted several turkey vultures, a common sight through Arizona’s warmer months. They started showing up a couple weeks ago, one of the earlier migrants we see every year. They are an easy bird to identify, even at great distance. In flight they hold their wings in a deeply angled dihedral. This simply means that if you were to look at the bird in head-on flight, its wings form a V shape. Many larger soaring birds do this to an extent, but it is an exaggerated characteristic of turkey vultures. Their wings are also “plank-like” and bi-colored. Much of the leading edge of the wing’s underside is a uniform black, in strong contrast with the silvery primary and secondary feathers. They soar in large interlocking circles, rarely flapping their wings. From this vantage, they are hoping to see or smell their food of choice, which is rotting carrion.

What does this have to do with the article’s title bird? Well, that description of a vulture in flight can also largely apply to the zone-tail, so much so it’s widely speculated that it uses this similarity to its advantage. For animals on the ground the sight of a vulture is common and of little concern; they know which animals pose threats — their lives depend on it. At the same time, they can’t needlessly exert energy by running from an animal that means them no harm. Vultures are only concerned with animals that are already dead, and zone-tailed hawks seem to understand this relationship. Consequently they will join groups of vultures, mimicking their every movement, even periodic teetering, the “unsteadiness” that vultures display while soaring. I have observed zone-tails doing this while with vultures, but not necessarily when they’re on their own, the idea being that animals on the ground will be lulled and lower their guard. At that moment the hawk will pounce.

For me this has always posed a very interesting question: is this knowledge inherent to the species, or is it taught by the preceding generation? Are they born knowing they look like vultures, and if not, how did they figure it out? They don’t have mirrors, so how is this communicated within the species? This is a defining behavioral characteristic, yet its genesis is largely a mystery.

Zone-tailed hawks occupy a variety of habitats, but while we can spot them in Arizona’s riparian corridors, I think of them as a higher-elevation, pine-forest species, making Prescott an ideal location to see them soaring overhead. For several years in a row we had a lone individual that would patrol the cemetery across from our shop. They prey on a range of small animals, from aquatic amphibians to small mammals. Zone-tails seem to me more opportunists than a specialists, which fits their behavior perfectly.

While in flight they are extremely similar to soaring vultures at a glance, there are several features that to provide a positive ID. The zone-tail has the same bi-colored wings, but where a vulture wing is silvery-smooth, the hawk has a more “textured” set of primary feathers. The bright yellow legs of the zone-tail are generally a dead giveaway, but the large white band across the tail confirms it.

As an interesting comparison, pull out your bird book and study the two species together. To complicate things, add the common black hawk to that study session.

At this time of year I tell all my bird-walk participants, “Check all your vultures, because it may be a zone-tailed hawk!” Happy birding!

Ryan Crouse manages Jay's Bird Barn.

The Prescott Audubon Society is an official chapter of the National Audubon Society. Check it out online at PrescottAudubon.org.