Continued Decline of the Northern Spotted Owl Associated with the Invasive Barred Owl, Habitat Loss, and Climate Variation plus 1 more

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Title: USGS Newsroom

Continued Decline of the Northern Spotted Owl Associated with the Invasive Barred Owl, Habitat Loss, and Climate Variation plus 1 more

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Continued Decline of the Northern Spotted Owl Associated with the Invasive Barred Owl, Habitat Loss, and Climate Variation

Posted: 10 Dec 2015 09:00 AM PST

Summary: Northern spotted owl populations are declining in all parts of their range in the Pacific Northwest, according to research published in The Condor.

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Contact Information:

Dawn Childs, USGS ( Phone: 571-643-1922 ); Mark  Floyd, OSU ( Phone: 541-737-0788 );

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CORVALLIS, Ore. – Northern spotted owl populations are declining in all parts of their range in the Pacific Northwest, according to research published in The Condor. Based on data from 11 study areas across Washington, Oregon and northern California, a rangewide decline of nearly 4 percent per year was estimated from 1985 to 2013.

Researchers found evidence that the invasive barred owl is playing a pivotal role in the continued decline of spotted owls, although habitat loss and climate variation were also important in some parts of the species range. Barred owls compete with spotted owls for space, food and habitat.

This research indicated that since monitoring began spotted owl populations declined 55-77 percent in Washington, 31-68 percent in Oregon and 32-55 percent in California. In addition, population declines are now occurring on study areas in southern Oregon and northern California that were previously experiencing little to no detectable decline through 2009.

Dr. Katie Dugger, a research biologist at the USGS Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University and lead author on the report, said that “This study provides strong evidence that barred owls are negatively affecting spotted owl populations. The presence of barred owls was associated with decreasing spotted owl survival rates in some study areas and spotted owls were disappearing from many of their historical breeding territories as those areas were invaded by barred owls.”

The exception was a small area in California where barred owl removals began in 2009, and where long-term population declines were only 9 percent. Spotted owl populations and survival rates have increased on the latter area since the removal of barred owls started. However, further research on barred owl removal is required in other parts of the spotted owl’s range -- especially in Washington, where barred owl numbers have been high for a long time. 

Additionally, said Dugger, "The amount of suitable habitat required by spotted owls for nesting and roosting is important because spotted owl survival, colonization of empty territories, and number of young produced tends to be higher in areas with larger amounts of suitable habitat, at least on some study areas." 

Relationships between spotted owl populations and climate was complex and variable, but rangewide, the study results suggested that survival of  young spotted owls and their ability to become part of the breeding population increased when winters were drier. This may become a factor in population numbers in the future, given climate change predictions for the Pacific Northwest include warmer, wetter winters.  

The collaborative team of 37 researchers analyzed data from 11 study areas that represented 9 percent of the spotted owl range. During the study, field crews monitored how many owls inhabited different territories, and the yearly survival and reproductive success of banded spotted owls. “This type of collaborative research focused on specific management and conservation objectives provides important information for resource managers and policy decision-makers who manage public resources,” said Eric Forsman, a coauthor on the study at the USDA Forest Service, Pacific Northwest Research Station.

The paper, “The effects of habitat, climate and barred owls on long-term demography of northern spotted owls,” was published in The Condor: Ornithological Applications and authored by Katie M. Dugger, USGS, Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University Department of Fisheries and Wildlife; Eric D. Forsman, USDA Forest Service, Pacific Northwest Research Station; Alan B. Franklin, USDA APHIS National Wildlife Research Center; Raymond Davis, USDA Forest Service, Pacific Northwest Region, and 33 others.

Although they do occur in young forests in some areas, northern spotted owls are strongly associated with old forest in most of their range. The U.S. Fish and Wildlife Service listed the northern spotted owl as threatened in 1990 because of the declines in old-growth forest habitat throughout its range in Washington, Oregon and northern California. 

 

 

New Tool Can Determine the Sources of Mercury Found in the Great Lakes

Posted: 10 Dec 2015 06:00 AM PST

Summary: For the first time, land and resource managers in the Great Lakes will be able to distinguish between the various sources of mercury in the environment, a toxic chemical of significant concern in the region

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Contact Information:

David  Krabbenhoft ( Phone: 608-821-3843 ); Alex Demas ( Phone: 703-648-4421 );

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For the first time, land and resource managers in the Great Lakes will be able to distinguish between the various sources of mercury in the environment, a toxic chemical of significant concern in the region. This is thanks to a new tool that “fingerprints” the mercury, developed by the U.S. Geological Survey and the University of Wisconsin-Madison. 

For Lakes Superior and Huron, atmospheric mercury is the dominant form, while in Lakes Erie and Ontario, most mercury comes from industrial activity or runoff from the watersheds of the lakes. Lake Michigan is dominated in some areas by atmospheric mercury, in other areas by industrial activity and in still others by watershed contributions.

A map showing the relative concentrations of mercury sources as identified by the fingerprinting tool. (High resolution image)

“I’ve been involved in mercury research for nearly 28 years,” said USGS scientist Dave Krabbenhoft, the project chief. “Back in the 1980’s, when I first got into this area of research, I dreamed of a tool that could provide geochemical markers of mercury sources.  That dream has now become reality.”

Determining where the mercury comes from is important, because it informs decisions designed to minimize it.  For example, minimizing industrial sources of mercury alone will not be effective if the majority of mercury entering the Great Lakes is from atmospheric mercury.

“One of the surprising things we saw was just how much of the mercury building up in fish was due to atmospheric mercury,” said Krabbenhoft. “This shows that atmospheric mercury needs to be emphasized, even when the sediments in the Lakes show relatively little atmospheric mercury accumulation.”

Although this fingerprinting tool was pioneered for the Great Lakes, it can be applied elsewhere. A very common situation across the United States and elsewhere is the presence of large amounts of mercury that was released during industrialization, so-called legacy mercury. At these sites, resource managers often lack a tool to help them understand whether it is legacy or other sources that substantively contribute to exposures in fish, wildlife and humans today.

“We are very excited to explore the capability of this new tool to inform resource managers and decision makers responsible for managing these challenging situations,” said Krabbenhoft.

Mercury is a naturally occurring element that can have toxic effects on people’s brains, kidneys and lungs. In certain environments, it can also bind with carbon and hydrogen to become methylmercury, which is far more toxic than elemental mercury. In addition, methylmercury can build up in the tissues of fish and other aquatic organisms, resulting in higher doses when people or other animals eat them.

More information about this new tool can be found online. USGS provides information on mercury sources; mercury cycling in the atmosphere, land surface, lakes, streams and oceans; and bioaccumulation and toxicity of mercury. This information helps land and resource managers understand and reduce mercury hazards to people and wildlife.