A very interesting article found online at the Arizona Republic

Zone-tailed hawk is a sign of coming spring

Uncommon bird can be seen around state

Jim Burns
Special for The Republic
Mar. 21, 2008 12:00 AM

A year ago in early March, this column spotlighted the common black-hawk, a unique migratory raptor whose return announces spring here in central Arizona. It’s that time of year again – perfect days, spring training, angst on Planet Orange – and again the arrival of a raptor, a different raptor unique in its own way but also in black plumage, that heralds the season.

The zone-tailed hawk, like the common black-hawk, is a buteo, the family of daytime raptors characterized by broad wings and short tails typically seen soaring overhead in midday thermals. Zone-taileds, however, have adopted an unusual hunting method known as behavioral mimicry, and are frequently seen soaring with groups of turkey vultures.

Zonies are beautiful, dark raptors with multiple white tail bands – one wide and one narrow on males, two narrow on females. From above, these bands will appear gray. When seen overhead, zonies soar with the dihedral (upswept wings) of the turkey vultures with which they often associate.

Here’s how behavioral mimicry works as practiced by zone-tailed hawks. With silvery flight feathers giving the same underwing appearance as the vultures and wings set in a dihedral, zone-taileds rock from side to side in flight like the vultures. Prey species (and birders), habituated to the more abundant, harmless, carrion-seeking vultures, dismiss the hawks as just another vulture. When a zonie in a kettle of vultures spots prey, it will continue to circle, but slip slowly lower and to the outside edge of its hosts, pass from sight behind intervening cover such as a rock or bush, then strike unexpectedly from behind the temporary concealment.

Seen soaring with the vultures or hunting individually, zone-taileds glide along slowly, appearing casual or even lazy, but they are capable of breathtakingly rapid, falcon-like stoops when prey is sighted. They subsist primarily on small mammals and lizards, but will also take large insects and small birds up to the size of quail, sometimes snatching them with their talons in full flight. Broken terrain may be the preferred habitat because the cover it provides is so well-suited to the hunting style these buteos have perfected.

Read the full article at the link above.