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For burrowing owls, city parks offer scant protection
More and more burrowing owls are settling into cities, but how do built environments affect their movement and survival?
Scientists in New Mexico found that burrowing owls — a state species of concern — were most likely to die in parks because of human intrusion in these relatively natural cityscapes.
“Urban habitats may act as ecological traps, said Martha Desmond, corresponding author on the study published in the Journal of Wildlife Management. “The birds are drawn in by high prey availability because we have a lot of lizards, small mammals and small birds, but they experience higher mortality rates in these habitats.”
All but a handful of the migratory burrowing owls (Athene cunicularia) that once visited Las Cruces, New Mexico, have been permanently pushed out of the city by development, which biologists anticipate will soon lead to the species’ local disappearance. Desmond, a professor with New Mexico State University’s Department of Fish, Wildlife and Conservation Ecology, and her partners fixed trackers on 42 remaining burrowing owl hatchlings before they fledged from nests here.
In 2012 and 2013, the researchers followed the birds across the patchwork of landscapes in and around town, from the highly urban parts to peripheral parks to agricultural sites consisting of field crops and pecan groves.
As they’d predicted, the birds in the most urban habitats had the most restricted movement, but the other results surprised them. The researchers expected birds in green spaces would fare the best, but it was just the opposite. Owls in green spaces had the lowest survival, they found. Survival was much higher in agricultural areas, where fields of short plants provide the open space and visibility the owls require.
Traditional farmlands cultivating short plants provide burrowing owls the open space and visibility they require, she said. The birds nest in burrows created by ground squirrels in irrigation canals above the field, which serves as a secure vantage point largely undisrupted by humans.
“Green space habitats are very popular in terms of people walking, jogging, walking their dogs and riding their ATVs, and it was an enormous amount of disturbance to these birds,” Desmond said. “Survival was substantially higher in these agricultural areas compared to urban and green space areas.”
The findings “have strong implications for how to select areas to release these birds” when relocating them from development to more suitable surroundings, Desmond said.
She and her collaborators are now investigating burrowing owl movement and survival in Phoenix, Arizona — where translocations move over 100 owls a year — to figure out how to best alleviate the pressure of urban development and promote their persistence.
“You would think green space habitats would be great for them, but they’re not, so you need to move these birds away from park areas adjacent to urban areas,” Desmond said.