Download Item 25 battistone atus Review for the Northern Spotted Owl

Status Review for the
Northern Spotted Owl
(Strix occidentalis caurina)
in California
Carie Battistone and Neil Clipperton
Senior Environmental Scientists
CDFW, Wildlife Branch
April14, 2016
Species Description
• Medium-sized dark
brown owl with white
spots on head, neck,
back, and underparts
• Dark brown, almost
black, eyes
surrounded by
prominent facial disks
CDFW Photo © Culpepper
Range
Range divided into 12
provinces, 3 of which
are in California
o California Coast
o California Klamath
o California Cascades
California
Range
Prey
Flying squirrels (Glaucomys sabrinus) and woodrats
(Neotoma sp.) are primary component of diet
throughout most of the range.
• Flying squirrels are main component in North (much of
Washington and Oregon)
• Woodrats are the main component in the southern
portion of the range (California and
parts of Oregon)
Woodrat, Santiago Oaks Regional Park, CA © Laura Cohen
Northern Flying Squirrel © Bob Cherry
Habitat
• Nesting and Roosting
• Foraging
• Dispersal (not discussed
here)
USFWS Photo
Habitat
Nesting and Roosting
Generally, nesting and roosting habitat includes:
o multilayered, multispecies canopy dominated by large
conifers (>30 inches dbh)
o well-developed understory of conifers or hardwoods
o high canopy closure (60-80 %)
o Large coniferous trees with
deformities, (cavities, broken
tops, dwarf mistletoe
infections)
o large snags
o accumulations of ground litter
(logs and other woody debris)
Spies and Franklin 1988
Habitat
Foraging
• Foraging habitat encompasses a wider range of
stand composition and structure than nestingroosting habitat
• Composed of variable-aged conifer stands and a
more diverse set of forest types (e.g., hardwood
forests) and structural characteristics:
o
o
o
o
o
old forest similar to nesting and roosting habitat
younger forests
hardwood stands
open areas with shrub habitat or woody debris
edge habitat
Status and Trends
Abundance
• No range-wide population estimate exists
• Pre-harvest surveys have dramatically increased
knowledge on location of territorial owl sites (i.e.,
activity centers)
• Densities vary across the range and forest types
o extrapolating the few local estimates across the range of the subspecies
would result in biased estimates of abundance
Northern Spotted Owl with young. USFWS Photo
Status and Trends
Abundance
As survey effort has
increased over
time, so has the
number of known
activity centers
o 3,116 as of 2014
Activity centers do
not necessarily
reflect current
abundance or
density
Status and Trends
Demographic Study Areas
• 11 study areas across
the range cover 9%
of the owl range
• 3 areas in California
o Northwestern
California (federal
land)
o Green Diamond
(private timber land)
o Hoopa (tribal land)
Status and Trends
Demographic Trends
Study Area
Fecundity
Survival
Territory
Occupancy
Population
Change
% Population
Change over
time
NWC
-55%
HUP
-32%
GDR
-9% to -41%
CAS (OR)
No trend
-44%
Status and Trends
Demographic Trends
Status and Trends
Occupancy
Declines in occupancy observed at all 11 study areas
since the 1990s
In California, occupancy
rates declined from:
• 79% to 47% at the NWC
• 74% to 38% at the HUP
• 92% to 55% at the GDR
In southern Oregon
occupancy rates declined
from 69% to 44%
Status and Trends
Occupancy
Interior study area
showed occupancy
declines around 40% for
both pairs and single
owls
Farber and Kroll (2012)
Status and Trends
Habitat Effects
Figure from http://woodlot.novascotia.ca/book/export/html/24
Spotted Owls benefit from a mosaic of forest types
containing sufficient old growth around the core,
interspersed with younger or other vegetation
types.
No more than about 50% of home range should
consist of nonhabitat.
Status and Trends
Habitat Effects
Spotted Owl fitness is
maximized in territories
that have a large
amount of older
forests, but that are
intermixed with
significant amounts of
earlier succession
vegetation types.
Franklin et al. 2000
Existing Management
14.3 million acres of
forested lands within the
Northern Spotted Owl
range in California
• 6.4 million acres are
publicly owned (45%)
• 7.8 million acres are
privately owned (55%)
Existing Management
• Federal lands largely governed by the Northwest
Forest Plan
• Nonfederal lands must
comply with the Forest
Practice Rules for
commercial timber
harvest.
Threats
• Habitat Loss
o
o
o
o
o
•
•
•
•
•
•
•
•
Timber harvest (conifer and hardwood) and regulatory mechanisms
Wildfire and salvage logging
Climate Change – forest composition and structure
Sudden Oak Death
Marijuana cultivation
Population status declines
Barred Owl
Disease
Climate Change – weather patterns
Contaminants
Predation
Recreational Activity
Loss of Genetic Variation
USFWS Photo
Threats
Habitat Loss – timber harvest
USFWS Photo
• Since 1993 (the development of a reserve system
under the NWFP), timber harvest on federal land
has declined.
• Conversely, timber harvest has been the primary
cause of habitat loss on nonfederal lands
Loss due to harvest on
federal land (acres)
CA Coast
Loss due to harvest on
federal and nonfederal
land (acres)
200
79,500
CA Klamath
10,400
50,100
CA Cascade
7,200
44,700
17,800
174,300
Total
Threats
Habitat Loss – timber harvest
interior activity center
USFWS Photo
coastal activity center
The minimum habitat retention requirements of owl habitat
do not appear to be sufficient at negating impacts to owls in
all cases.
Threats
Habitat Loss - Wildfire
Wildfire suitability modeling compared to actual
fire map
USFWS Photo
Threats
Habitat Loss - Wildfire
USFWS Photo
Most loss occurred on federal land in the California
Klamath Province.
Federal Lands
Loss due to Wildfire on
federal land (acres)
Loss due to Wildfire on
federal and nonfederal
land (acres)
1,800
5,600
CA Klamath
199,800
208,100
CA Cascade
7,200
10,500
208,800
224,200
CA Coast
Total
Threats
Habitat Loss - Wildfire
USFWS Photo
Conditions that support more frequent, large, and
more severe fires are projected to increase due to
climate change. Habitat loss due to wildfires will likely
continue.
Davis et al. 2011
Threats
Barred Owl
• Native to eastern North
America
• Expanded into western
North America
• Occur throughout the
range of the Northern
Spotted Owl.
Livezey 2009
USFWS Photo
Threats
Barred Owl
Today, nearly 2,000 Barred
Owl records exist within
the Department’s species
database.
USFWS Photo
Threats
Barred Owl
USFWS Photo
Documented impacts from Barred Owls include
 altered behavior of Spotted Owls (e.g., reduced
calling),
 displacement of Spotted Owls from preferred
high quality habitat,
 decreased survival and occupancy rates, and
 increased territory extinction rates
Threats
Barred Owl
Mendocino Redwood Company 2014
Annual Report
Hoopa 2013 Report
USFWS Photo
Humboldt Redwood Company 2014
Annual Report
Dugger et al. 2016 – CA study areas
Threats
Barred Owl
USFWS Photo
Diller et al. 2016
Results indicate that removal appears to be
successful at mitigating the negative impact to
Spotted Owls and are feasible at least at a localscale.
Conclusion
• There are steep and accelerating declines in NSO
population and vital rates
• Primary threats to the continued existence of NSO in
California are:
o rapid expansion the Barred Owl into the range of the NSO
o rapid and accelerating decline in population size and vital
rates
o loss of habitat due to wildfire and timber harvest
• These coupled with other threats (climate change,
impacts of marijuana cultivation, disease, Sudden Oak
Death) will lead to additional declines unless additional
management intervention is undertaken.
Recommendation
The best scientific information available
indicates to the Department that the
petitioned action is warranted, and the
Department recommends to the
Commission that the Northern Spotted
Owl be listed as Threatened under the
California Endangered Species Act.
© Robert Hawkins
Questions?