Report on save forest owl
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The forest owlet (Athene blewitti) is an endangered owl that is endemic to the forests of central India. The species belongs to the typical owls family, Strigidae. First described in 1873, it was not seen after 1884 and considered extinct until it was rediscovered 113 years later in 1997 by Pamela Rasmussen. Searches for the species in the locality given on the label of the last collected specimen failed and it was discovered that the specimen had been stolen from the British Museum by Richard Meinertzhagen and resubmitted with a label bearing false locality information.It is known from a small number of localities and the populations are very low within the fragmented and shrinking forests of central India.
The previous tree canopy guidelines were largely drawn from past studies showing that spotted owls were more prevalent in forests with 70 percent or higher tree canopy cover. But those studies could not distinguish whether the presence of tall trees or high canopy cover were more important to the owl.
For this study, scientists used the relatively new technology of Light Detection and Ranging imaging, or LiDAR. The tool uses laser pulses shot from an instrument mounted in an airplane to measure a forest’s canopy in detail. The study’s authors used it to measure the height and distribution of tree foliage and forest gaps across 1.2 million acres of California’s Sierra Nevada forests.
Researchers used LiDAR imaging, such as this point cloud representing good habitat for spotted owls, to determine that tall trees rather than total tree cover are most important for spotted owls. (Credit: Jonathan Kane/U. Washington)
“Field-based studies of forests are expensive and time-consuming, which means that measurements are generally taken over areas a fraction of an acre,” says coauthor Van R. Kane, an assistant research professor in the School of Environmental and Forest Sciences at the University of Washington. “We believe this is the largest spotted owl study yet in terms of the area of forest examined.”
The authors also used a data set collected by wildlife researchers spanning more than two decades that recorded the positions of 316 owl nests in three national forests and Sequoia and Kings Canyon national parks.
They found the owls seek out forests with unusually high concentrations of tall trees measuring at least 105 feet tall but preferably taller than 157 feet. These tall trees also tended to be areas with high levels of canopy cover. However, the owls appeared to be indifferent to areas with dense canopy cover from medium-height trees and avoided areas with high cover in short (less than 52 feet tall) trees.
“The analysis helps change the perception of what is important for owls—the canopy of tall trees rather than understory trees,” says coauthor and spotted owl expert R.J. Guitiérrez, a professor emeritus at the University of Minnesota. “The results do not mean a forest should be devoid of smaller trees because owls actually use some of those smaller trees for roosting. But it suggests a high density of small trees is likely not necessary to support spotted owls.”
Additional coauthors of the study are from the USDA Forest Service Pacific Southwest Research Station, the University of Washington, Stanford University, the University of Wisconsin-Madison, the US Forest Service Region 5 Remote Sensing Laboratory, the University of Minnesota, Tahoe National Forest, and UC Davis.
The USDA Forest Service funded the data analysis. The David and Lucile Packard Foundation and the US National Park Service funded the Carnegie Airborne Observatory data collection and processing.
The researchers report their findings in the journal Forest Ecology and Management.