Researchers connect a GPS transmitter to a captured owl. Credit score: Nick Kryshak

Within the Pacific Northwest, the vary enlargement of Barred Owls has contributed to a conservation disaster for Northern Noticed Owls, that are being displaced from their old-growth forest habitat. How will this interplay between species play out within the Sierra Nevada, the place Barred Owls are simply beginning to transfer into the vary of the California Noticed Owl? New analysis revealed in The Condor: Ornithological Functions means that wildlife managers should be capable of head off comparable issues in crucial areas of the Golden State — in the event that they act now.

The College of Wisconsin’s Connor Wooden and his colleagues used passive acoustic monitoring to survey Barred Owl populations over two years, deploying audio recorders over an space spanning greater than 6,000 sq. kilometers throughout two nationwide forests in northern California. Finding owl calls within the audio information allowed them to find out which internet sites have been and weren’t occupied by owls. They discovered a 2.6-fold improve within the quantity of territory occupied by Barred Owls between 2017 and 2018, and the previous forest habitat most well-liked by Noticed Owls was the most certainly to be colonized.

Passive Acoustic Recording Unit

Passive acoustic monitoring utilizing units like this one let researchers monitor the presence of owls throughout an enormous space. Credit score: Connor Wooden

Populations of invasive species sometimes stay at low densities for a number of generations earlier than rising quickly. As a result of intervening to manage a doubtlessly damaging invasive species requires many assets, land managers typically await robust proof species will pose a menace earlier than taking motion. However, by the point the “progress part” has began, it’s typically too late. Wooden and his colleagues consider their outcomes present that the expansion part of the Barred Owl inhabitants within the area is simply starting, that means wildlife managers nonetheless have time to behave. Solely a slender band of pretty unsuitable habitat connects the present Pacific Northwest inhabitants of Barred Owls to the Sierra Nevada stronghold of California Noticed Owls, and the researchers advocate experimentally eradicating Barred Owls from the Sierra Nevada facet of this pinch level to see if this could forestall them from turning into established additional south.

“We steered that managers act based on the Precautionary Precept: when there’s a severe menace to human well being or the atmosphere, proactive responses are justified even when there may be some uncertainty,” says Wooden. “We really feel that experimental Barred Owl removals within the Sierra Nevada are an essential step in figuring out one of the best long-term administration technique. This isn’t one thing that anybody takes frivolously, however we really feel that it’s warranted due to the very actual risk that continued Barred Owl inhabitants progress may significantly endanger the California Noticed Owl. By catching this invasion within the early levels, we have now a singular however doubtlessly fleeting alternative to tell insurance policies that would forestall the California Noticed Owl from being pushed extinct within the core of its vary.”

Reference: “A speedy improve of Barred Owls within the Sierra Nevada advises the Precautionary Precept” by Connor M Wooden, R J Gutiérrez, John J Keane and M Zachariah Peery, 22 January 2020, The Condor: Ornithological Functions.
DOI: 10.1093/condor/duz058


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