Population demography Monitoring Program
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We conduct long-term monitoring of spotted owl populations (Strix occidentalis caurina) on the Olympic Peninsula and Cle Elum study areas in WA, and in OR we conduct this work on Oregon Coast Range, Tyee, and Klamath study areas. The overarching purpose of this long-term research is to understand the effectiveness of federal forest management, especially the Northwest Forest Plan, for maintaining and restoring conditions necessary to support viable populations of spotted owls on federally-administered lands. Through this work we track status and trends of spotted owl populations primarily by collecting data to quantify territorial occupancy, survival, reproductive success, and annual rate of population change. We quantify the effects of trends in the amount and distribution of suitable forest and other components of spotted owl habitat such as presence of barred owls and prey species.
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synthesis of spotted owl research under Northwest forest plan
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The U.S. Forest Service Pacific Northwest and Pacific Southwest Research Stations developed a synthesis of science relevant to outcomes under the Northwest Forest Plan. The science synthesis was published in 2018 and is being used to to inform the revision of forest plans for 19 national forests within the Northwest Forest Plan area. Dr. Lesmeister led the chapter on northern spotted owls, which synthesized research on populations, habitat, threats, and provided a prognosis for future spotted owl populations. In short, what we found was that spotted owl populations are in steep decline and face many threats including negative effects of past and current loss of suitable forest caused by timber harvest and wildfire. Additionally, several lines of evidence have documented the negative impacts of barred owls (Strix varia) on spotted owl populations. Regarding the effectiveness of the Northwest Forest Plan and spotted owls, we concluded that the plan has been critical for spotted owls because populations certainly would have declined more rapidly had it not been for protections afforded under the plan. We also suggest that the plan by itself is not sufficient to reverse trends in populations, thus additional conservation and management measures are likely needed to improve population status of northern spotted owls. See publications tab for links to papers published from this effort.
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3-dimensional partioning between spotted owls and barred owls
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Patrick Kolar
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Dr. Jenkins is the lead author on a paper providing the first evidence of fine-scale spatial partitioning between spotted owls and barred owls based on structural forest properties. We examined resource selection by sympatric northern spotted owls and barred owls in western Oregon to quantify the relative importance of canopy heterogeneity, vertical complexity of forest, and abiotic features and identified potential differences that may facilitate long-term coexistence. Our results suggested that while both species used tall canopy areas more often than low canopy areas, spotted owls were more commonly found in areas with lower tree cover, more developed understory, and steeper slopes. Published paper coming soon!
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activity center selection
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Dense forest canopies are often reported as an important habitat attribute for spotted owls, though the means of measuring forest canopy and interpreting species requirements vary across studies. Stan Sovern is the lead author on a paper where we demonstrated the effectiveness of lidar data to accurately measure forest canopies over large areas, and assist in mapping spotted owl habitat, especially critically important activity centers that are often used for nesting. We used lidar measurements of canopy cover, canopy surface heterogeneity, and upper canopy surface connectivity. Spotted owls selected activity centers with more canopy cover and higher heterogeneity of the canopy surface within 100 m than was available within their territories. Published paper coming soon!
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mixed-severity wildfire and spotted owl habitat
Maps showing a) Klamath-Siskiyou Ecoregion of California and Oregon, USA (hatched area); b) historical fire regimes in the Klamath-Siskiyou Ecoregion, Klamath northern spotted owl demography study area (1422 km2; center = 123.315°W, 42.782°N, heavy black border); and c) land ownership (federal land gray, private land white) and the 2013 Douglas Complex and Big Windy Fires (cross hatched area).
Forests that were suitable for nesting and roosting had higher odds of burning at low severity rather than moderate or high severity. Unsuitable forests had the opposite odds, in that they were more likely to burn at moderate or high severity compared to low severity.
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During severe fire weather in 2013, a complex of mixed-severity wildfires burned across multiple ownerships within the Klamath-Siskiyou ecoregion of southwestern Oregon where northern spotted owl demographics have been studied since 1990. The forests used by spotted owls for nesting and roosting before the fire had typical characteristics of old-growth forest, with high density of large live trees, high canopy cover, and complex structure in canopy height. Dr. Lesmeister is the lead author on a paper that used pre- and post-fire lidar to quantify wildfire impact on northern spotted owl nesting/roosting habitat. As expected, pre-fire habitat was nearly eliminated if it burned at high-severity. Low-severity fire had minimal influence on habitat. We also quantified the probability that pre-fire nesting/roosting habitat would burn at each severity class (unburned/low, low, moderate, high). Contrary to commonly held expectations, pre-fire nesting/roosting habitat had lower probability of burning at moderate- or high-severity compared to other forest types under severe burning conditions. Our results indicate that northern spotted owl habitat is more resistant to high-severity fire and can buffer the negative effects of climate change by enhancing biodiversity and resistance to high-severity fires. Published paper coming soon!
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