Red-tail on the hunt at Fermilab, Batvia, Ill. Photo courtesy of Gregory Vogel

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Readers of the Sept. 2, 2009 issue of the RoundTable may recall the column “The Hawks versus the Martins,” describing a red-tailed hawk raiding purple martin houses for nestlings along Evanston’s lakeshore.

In late September, long after the martin adults had abandoned their nesting sites, our correspondent continued the saga: “Today a large Red-tailed took up a hunting perch in the dead tree at the fence line…. Then a second hawk appeared and perched on the same branch about 10 feet away. And there they both perched, scanning the dunes, for at least 20 minutes.  Then one made a dive for a prey, missed, and flew to another tree just out of out of our sight. We thought hawks were solitary, so this surprised us.”

A quick search of Cornell University’s Birds of America Online revealed that hawks engage in “cooperative hunting, when two hawks guard opposite sides of a tree, sometimes to catch tree squirrels.”

Red-tails are raptors, that is, carnivorous birds of prey that kill with their feet. Their curved, sharp talons seize prey (raptor is from the Latin rapare meaning to seize or grasp) and their strong, short hooked beaks tear it apart. Their keen eyesight is more complex than that of humans, allowing them to spot prey at a great distance, track and capture it.

They are our most common buteo – short-bodied hawks with broad wings, proportioned for easy and graceful soaring over open country. The female is somewhat larger than the male. Their wingspan can exceed 48 inches, they can be 18 inches tall, and can fly 35 to 40 mph. Their large size is deceptive, however, because their average weight is only three pounds. They have been known to catch five-pound prey.

These imposing birds have brownish backs and light bellies, some with longitudinal streaking, some plain white. There is tremendous plumage variation, but adults have an unmistakable fanshaped red tail that seems to glow if you catch the bird banking up high in bright sunlight. Legs and feet are yellow, talons are jet black. Immatures have brown tails with horizontal black bands. Tails become red in the second year when they are ready to breed. According to a Hopi account, “The red tail of the hawk only appears when the bird reaches maturity… [indicating] that the Red Feathers are not easily given, and must instead be earned over time. Hence, the symbolism of the Red Tail Feathers emerging only with age and experience.”

Red-tails are active during the day. They typically prey on small to medium-sized mammals like mice and voles, especially cottontails, and some birds. (They may eat only the nutritious head of oversized prey.) Immatures may hunt by soaring overhead but adults usually “perch-and-wait.” The previous popular nickname, chicken-hawk, has been officially discontinued. In his chapter titled The Red-tailed Buzzard, however, John James Audubon says the red-tail “visits the farmhouses to pay his regards to the poultry.” Contemporary accounts verify the red-tail’s occasional sampling of chicks but highly value its control of rodents.

Red tails are generally monogamous and may stay together for years in the same territory, which can range from a half square mile to 9.6 square miles.

Around late February, both male and female red-tails start their dazzling aerial courtship and territorial displays. To view this performance, The Stokes Guide to Bird Behavior advises visiting a nest area around mid-morning, where “you are very likely to see the displays of Talon-drop, Undulating Flight, accompanied by a loud scream and perhaps ending in the Dive-display, during which the male quietly aims its dives over the nest area.” They soar on clear days when the sun warms the earth and creates rising thermals, which the hawks use for lift. Thermals usually begin in late morning, prime hawk-watching time.

Nests of twigs are built near a treetop in the crotch of sturdy branches close to the trunk. Softer materials, including shredded bark, grapevines, moss, and evergreen needles line the interior. Both male and female build the nest, which may be completed within a week. An active nest is continuously replenished with greenery. Nests may be reused, sometimes alternating with Great-horned owls, and if used over a period of years they may exceed three feet in height and width. A lofty oak on the Northwestern Campus near Sheridan Road and Chicago Avenue held a nest two years ago.

A month can pass between completion of the nest and egg-laying. In our vicinity, a pair averages two eggs. The female usually incubates the eggs, with the male responsible for feeding her. Incubation averages one month. Newly-hatched young are covered with white down and begin to grow feathers at around 16 days. Nestlings remain in the nest for a month and a half. When they first leave the nest, they hang around their natal grounds, but after a month they mostly fend for themselves.

The red-tail is a North American bird with a transcontinental range, breeding as far north as Canada. Their year-round range includes the continental United States, Baha California, the Caribbean east to the Virgin Islands, and parts of Central America. They were recently found in Venezuela. Red-tails that breed in Canada may migrate far to the south or to our vicinity. First year birds probably winter in the south. Many adults are permanent residents here and are regularly tallied on Evanston North Shore Bird Club Christmas counts.

Attention Purple martin landlords: get those owl (red-tail) guards ready for spring!