Model explains barred owls' domination over northern spotted owls

Date: December 1, 2016

Source: Michigan State University

Barred owls -- unrivaled nocturnal predators and procreators -- are moving into the Pacific Northwest. They're encroaching on northern spotted owl territories and outcompeting this smaller, threatened cousin.

A model developed at Michigan State University shows how it's happening and gives wildlife conservationists a highly accurate, yet cost-effective tool to help shape management policies.

"Our model estimates population abundance and demographic rates, such as survival and reproduction, from relatively 'cheap' data," said Sam Rossman, postdoctoral researcher with MSU and Hubbs-SeaWorld Research Institute and the paper's lead author. "Typically, estimating these quantities requires intensive sampling efforts involving capturing, marking, releasing animals and then repeatedly tracking and recapturing them at later dates."

The MSU model is featured in the current issue of Ecology and uses data on two simple factors: presence or absence of animals across space and time. While the input may be simple, the model is not. "Dynamic N-occupancy" is capable of providing accurate estimates of local abundance, survival rates and population gains -- including reproduction and immigration -- while accounting for the fact that the presence of a species may be detected imperfectly during sampling.

"Simply put, the model is telling us the rate at which barred owl numbers are increasing and offering clues as to why that's happening. This, in turn, can help us understand how endangered spotted owl populations in the same region may respond," said Sarah Saunders, MSU postdoctoral researcher and one of the paper's co-authors. "Barred owls are bigger, more aggressive, maintain a smaller territory, produce more young and are even outcompeting spotted owls in old-growth forests, what was once thought to be spotted owl strongholds."

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Biologists Kill Bully Owls to Protect Endangered Owls

By THE ASSOCIATED PRESS

SAN FRANCISCO — Feb 28, 2016, 7:06 PM ET

A biologist and contractor with a lumber company is at the heart of an experiment sanctioned by the U.S. Fish and Wildlife Service: killing bully owls to protect endangered owls.

Biologist Lowell Diller, a contractor for Green Diamond Resource Co., a lumber company managing timberland in Humboldt, Del Norte and Trinity counties, kills barred owls, which are known to bully the smaller northern spotted owl, the San Jose Mercury News reported (http://bayareane.ws/1QlXvDn).

The barred owl has invaded California from the eastern United States, muscling out northern spotted owls upstate, and spreading south toward San Francisco. A Pacific Northwest native, the spotted owl is threatened with extinction and has become the symbol of the region's timber conservation battles.

Northern spotted owl populations have fallen in some areas by about 12 percent each year, despite efforts enacted in the 1990s to protect their old-growth forest habitat.

After Diller learned Jack Dumbacher, ornithology curator at the California Academy of Sciences, had a permit to collect some barred owl specimens, Diller saw an opportunity and applied for his own permit.

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THREATENED SPECIES: Threatened Owls Pushed Out of Home by Foes

By Megan Gannon, News Editor | February 25, 2014 06:03pm ET

northern spotted owl

A threatened species of owl is losing a turf war in the Pacific Northwest.

Northern spotted owls are getting edged out of their already declining habitat by invading barred owls, a new study finds.

barred owl

Researchers pored over 22 years of data from a study site in Oregon covering 386 square miles (1,000 square kilometers) where the habitats of the two species overlap. In this area, both owl species were more likely to abandon a neighborhood when their rival was present, the researchers found.

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Feds advance plan to kill barred owls in Northwest

GRANTS PASS, Ore. Federal wildlife officials plan to dispatch armed bird specialists into forests of the Pacific Northwest starting this fall to shoot one species of owl to protect another that is threatened with extinction.

The U.S. Fish and Wildlife Service on Tuesday released a final environmental review of an experiment to see if killing barred owls, which are bigger, more aggressive and less picky about food, will allow northern spotted owls to reclaim territory they’ve been driven out of over the past half-century.

The agency has been evaluating the idea since 2009, gathering public comment and consulting ethicists, focus groups and scientific studies. It will issue a final decision on the plan in a month.

“If we don’t manage barred owls, the probability of recovering the spotted owl goes down significantly,” said Paul Henson, Oregon state supervisor for Fish and Wildlife.

The agency’s preferred course of action calls for killing 3,603 barred owls in four study areas in Oregon, Washington and Northern California over the next four years.

The plan is expected to cost about $3 million and requires a special permit under the Migratory Bird Treaty Act, which prohibits killing nongame birds.

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