Night Stalkers, Night Talkers

the sentinels of the night emerge from daytime hideaways, and with silent flight swoop to saguaros and limbs of paloverde trees. Owls come in a variety of sizes, some but a single handful of fluffy feathers, others with wings spanning 4 feet. Their sound, not their form, reveals their presence.

More than any other birds, owls' voices demand immediate and total attention. Noises in the dark have that effect. Without visual clues, sound matters, which might explain why so much mythology swirls around these creatures and why owls, with a language all their own, remain distinct from all other birds.

Like most birds, each owl species has many calls used in different circumstances. Those calls most familiar to humans are ones that signal territory or aggressive intent to chase away an adversary. The call of each owl species has a singular tone, cadenceand intensity, and, as in all birds, the owl has its own unique vocabulary. When blended with other owls' calls, it comprises a language that permeates the desert night. In springtime the calls mix with the clamor of crickets and insects, but in winter the owls' songs are chilling and alone.

Through December and January, the great horned owl, Arizona's largest species, starts broadcasting its familiar hoho hooo hoo call into the southern Arizona darkness. With these mournful notes, the bird lays claim to a prospective nesting territory. In the months to follow, other owl species will join in the chorus of declarations.

The Western screech owl has the most distinctive utterance, sounding much like a bouncing ball. A golf ball that's dropped into a wooden barrel from a height of 2 feet makes a similar sound. The initial "hit of the ball" sounds the loudest, and repetitive "bounces" are more frequent and subdued, trailing off into silence. Hardly the "screech" that this owl's name suggests.

Screeching, however, does identify the barn owl. A throaty, raspy, scratchy shriek emitted over urban or agricultural areas in the Sonoran Desert probably comes from a barn owl.

In similar places, especially around agricultural areas, a sound akin to a rattlesnake's rattle may indicate a burrowing owl. This is not a territorial signal, but rather a very effective defense used by young owls to ward off anything that sticks its nose down their burrow.

The ferruginous pygmy-owl gives a single-note call that is repeated monotonously for several minutes. The song of the male elf owl consists of a series of puppylike yips. Finally, the long-eared owl offers the most eerie resonance, a low-pitched hooo series that frequently leaves humans who hear the sound asking the same "question."

Thirteen species of owls find homes in Arizona's varied habitats, and though some may seasonally occur in the Sonoran Desert, only seven species establish nesting territories there. The great horned owl and long-eared owl have the most widespread distributions, occurring from the deserts up to the coniferous forests. The barn owl, Western screech owl and elf owl live in desert areas all year, but also range into woodland and forest habitats of the state, and the burrowing owl lives in burrows in agricultural areas and grasslands. Within Arizona, the endangered ferruginous pygmy-owl occurs only in the Sonoran Desert, where it remains year-round.

In general, owls are not shy around humans, and they often take up residency in areas of human habitation if food is available. In southern Arizona cities, the barn owl sometimes nests in palm trees, preying on small mammals that occupy suburban open space and on nestling pigeons that also commonly inhabit palm trees. An individual long-eared owl takes up recurring residency in an ornamental pine tree at Tucson's Tohono Chul Park from about October through February, the most regular winter occurrence of that species in the Tucson vicinity.

The burrowing owl also has close association with human endeavors, making it readily visible. This long-legged hunter frequently resides around

the fringe of agricultural areas and other open country, where insects, small rodents and lizards are plentiful. One burrowing owl near Yuma had the habit of perching near a convenience store parking lot at night and grabbing insects that fell to the ground beneath a streetlight.

The diets of different owl species have much in common. Owls dine on insects, rodents, mammals and sometimes even other birds, all of which are abundant in the Sonoran Desert. Owl species avoid competition with each other by establishing territory within a habitat and hunting different-sized prey.

The tiny elf owl, the smallest owl of North America at 5.5 inches in length, leaves the Sonoran Desert during winter when much of its food source, anthropods like scorpions and centipedes, lies dormant and protected in the ground or under rocks. This insect specialist retreats to warmer climes of Mexico, where its prey still meanders about after sunset.

The great horned owl captures larger prey such as skunks, ringtailed cats and cottontail rabbits. The barn owl and long-eared owl are specialists on medium-sized rodents like kangaroo rats, and the Western screech owl and burrowing owl grab smaller mice and insects. The ferruginous pygmy-owl has ferocious predatory skills. Slightly larger than the elf owl, it will grab nearly all forms of prey, including insects, small mammals and birds that are even larger than itself, but half of its diet may consist of lizards.

The pygmy-owl becomes active during the day, especially adults with young to feed. Since they are excellent predators, other local birds neighboring their territory will ceaselessly chase pygmy-owls that leave their secretive perches to pursue quarry.

Owls are especially equipped to hunt at night by their superb sense of hearing. A ring, or disk, of feathers on their faces directs sound waves toward the ears. This facial disk is especially evident in the barn owl; the developing feathers of young barn owls reveal this facial pattern very early. The ears, one angled upward and the other downward, enable the owl to locate prey even on moonless nights.

Since owls frequently swallow prey whole and digest bone and fur incompletely, they cast up undigested material like the scales, feathers and skulls of their prey in a mass called a pellet. Beneath its favorite daytime roosting perch, an owl will regurgitate these pellets, each one being a detailed assessment of the previous evening's meal.

The pellets contain information documenting the incredible diversity of Sonoran Desert wildlife a story told in yet another language, by the winged masters of the desert night. All Rich Glinski of Wickenburg retired from the Arizona Game and Fish Department and currently supervises Maricopa County's Desert Outdoor Center at Lake Pleasant. He has edited and written several works on birds, including Birds of Prey in the American West, with photographs by Tom Vezo. Tom Vezo of Green Valley admits he's not a night person, but says the change to the dark shift while capturing owls on film was challenging and enjoyable.

Driving down a dirt road rough enough to rip the bottom from a sedan, photographer Charles Lawsen steered the pickup truck over ruts and volcanic boulders as I held on tightly against the jostling motion. We were headed for Pueblo Las Mujeres, a 1,500-year-old native ruin on Perry Mesa, 55 miles north of Phoenix, and getting there wasn't easy.

Lawsen and I exchanged a meaningful look and burst into laughter. With mean roads like this, we figured ma and pa and the kids wouldn't show up out here in the family car any time soon. For us to get this far involved rocking and rolling across a high desert savannah on a road cobbled by lava bombs hurled from Joes Hill, an extinct volcano.

Stunted junipers and wild grass bleached nearly platinum by sun and continuous drought lends a primitive beauty to this weary land. Most people would not want to live here, and we were left to wonder how ancient people managed with only sticks and stones.

When we finally stopped, like a sailor testing his sea legs, I felt grateful for firm footing again as I faced a defensive perimeter of dry-laid boulders. Beyond the redoubt, arranged along the crest of precipitous Squaw Creek canyon, we could see the rubble of 200 rooms occupied for perhaps 300 years, before the residents disappeared around A.D. 1400, leaving little record of themselves except petroglyphs chiseled into a basalt ridge.

During the following weeks, Lawsen and I visited five of the mesa's seven major archaeological sitesone of the largest concentrations of ancient sites in Arizona. Visitors can drive to four of them-Las Mujeres, Brooklyn and Rosalie Mine groups, all in the Tonto National Forest, and to Pueblo La Plata Ruin in the 71,000-acre Agua Fria National Monument. But to see the rema ining three-Pueblo Pato, the Baby Canyon and Lousy Canyon groups-expect to

Perry Mesa sites tell stories of a tough existence