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NMSU Researchers Studying Mexican Spotted Owl Habitat

LAS CRUCES - Five years ago, not much was known about the Mexican spotted owl and its habitat. Since then, New Mexico State University wildlife researchers have helped unravel some of the mysteries of the northern spotted owl's less controversial cousin.


"Of the three spotted owl subspecies, only the California subspecies is thought to be secure in the wild," said Phillip Zwank, leader of the New Mexico Cooperative Fish and Wildlife Research Unit. "The northern and Mexican spotted owls are listed as threatened because of low population numbers and decreasing habitat from timber harvesting."

The northern spotted owl was the source of recent controversy between environmentalists and the timber harvesting industry in the northwest. Studying Mexican Spotted Owl Habitat

While there have been many studies of the habitats and ranges of the California and northern spotted owls, only a few researchers have looked at the characteristics of the Mexican spotted owl. "What we did know was that the owl lives in very disjointed forest habitats, primarily in the Lincoln and Gila national forests," Zwank said. "We thought that maybe this species would have less distinct and not as highly defined habitat needs as the northern spotted owl."

To find out more about the birds, the researchers tracked 17 adult owls through their nesting period. They followed the birds by radio-tagging nine adults, eight of which were paired.

"We found that the owls roosting in what would be considered in the north as old growth forest," he said. "What we have here in the Southwest is higher elevations that allow the same mix of trees that the northern spotted owl uses."

The owls in the study primarily were found in mixed-conifer forests in very steep canyons that had not been harvested since the turn of the century. "They lived in less dense areas than the northern spotted owls, and they were able to use some alternate habitats" Zwank said. "They would forage and roost in some younger forests, but most of the nesting was in the old, large trees like the Douglas firs and the white firs."

Most of the birds are occupying areas that are under the control of the U.S. Forest Service, Zwank said. "If the Forest service continues to allow for their existence, the population should continue from now on," he added. "Another good sign was that the birds in the study were reproducing," Zwank said.

On average, the owls lived in ranges of about 1,800 acres each, the study showed. That's a range 14 percent larger than reported for Mexican spotted owls living in Arizona. "The study was most helpful for identifying where the owls are located. We identified nest sites, so wildlife managers can check to see whether the same pairs of birds are occupying the same habitat year after year," Zwank said. "Also, if this habitat is modified in the future by timber harvesting, we can monitor what happens to the owls that live there."

Results of this study were published in the Journal of Field ornithology.

The New Mexico Cooperative Fish and Wildlife Research Unit includes NMSU, the U.S. Fish and Wildlife Service, the New Mexico Department of Game and Fish, and the Wildlife Management Institute.