science to inform adaptive management for ravens · 2017. 11. 6. · • impact state-wide maps...
TRANSCRIPT
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Science to Inform Adaptive Management for Ravens
U.S. Geological Survey, Western Ecological Research Center Partners: Nevada Department of Wildlife, Idaho State University, Oregon State University
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Breeding Bird Survey Data
Detected ravens at ~40% of surveys
(BBS; Sauer and Link)
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Breeding Bird Survey Data
Detected ravens at ~80% of surveys
Increased number of
observations per detection
(BBS; Sauer and Link)
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Raven Population Growth within Great
Basin BCR
~230% increase
Raven Counts Currently: • Great Basin to >15 • Sonoran and Mojave to >10 • Coastal CA to >15 • Southern Rockies/Colorado
Plateau to >20 No Decreases
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William Boarman, USGS 0
2
4
6
8
10
1960 1970 1980 1990 2000 2010
Year
Co
un
t
Raven Numbers
300% Increase, 1966-2007
n = 1,226 P < 0.001
Sauer et al 2007
Sauer et
al. 2004
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Unnatural Nest Substrate
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Findings
• 1-km increase in distance to power line decreased selection by 31%
• 100-m increase in distance from edge decreased selections by 20%
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• Included non-resident (non-breeding) ravens – selected at larger spatial scales
• Effect of transmission line greatest within 2.2 km (4.5 km corridor)
• Additive effects of energy infrastructure
and altered land cover types
Increased land cover edges, non-native vegetation, and patchiness
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73 41
28
21
16
27 38
0
10
20
30
40
50
60
70
80
Ju
ve
nile
su
rviv
al (%
)
Nest distance to nearest anthropogenic resource (km)
(χ2 = 16.8, P < 0.001)
ANTHROPOGENIC RESOURCES INCREASE
SURVIVAL TO DISPERSAL (CA)
Webb et al. 2004 Condor 106:517-528
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Raven
Populations
Prey Population
Vital Rate
Habitats
of Prey
Anthropogenic
Subsidies (e.g., food sources,
nest substrate)
Anthropogenic Factors Indirectly
Affect Prey
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Indirect Effect – Nest Predation
Common Name
Raven
Impact #
Sources
Likely or
Potential
Raven
Impact
USESA (Year
Listed) U.S. States
Desert Tortoise Numerous High T (1980) T (CA, UT); S2 (AZ)
Piping Plover Limited Low E / T* (1985) E (DE, MD, ME, NC, ND, NH, NJ), S2B (MT); T (CO,
FL, GA, KS, MA, NE, NM, VA; CT, SD, TX); SP (AL)
Greater Sage-Grouse Numerous High NL T (WA); S2 (ID); S3 (NV); SC (CO, UT)
Roseate Tern Limited Low E/T^ (1987) Ex (MD); E (MA, ME, NC, NH, NJ, NY, CT); T (FL)
Marbled Murrelet Numerous High T^^ (1992) E (CA); T (OR, WA)
San Clemente Loggerhead Shrike Limited Unknown E (1977) NL
California Condor Limited High E/T*** (1967) E (CA)
Gunnison Sage-Grouse Limited High T (2014) SC (CO); T (UT)
Greater Sandhill Crane Numerous High NL E (WA); T (CA); S3B (ID); SC (CO)
California Least Tern Numerous High E (1970) E (CA, OR)
Western Snowy Plover Numerous High T^^^ (1993) T (OR); SC (CO)
Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
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Common Raven 53% American
Badger 25%
Bobcat 3%
Coyote 14%
Long-Tailed Weasel
5%
Impacts on Sage-Grouse (9 years of video data)
Literature: Coates et al. 2008. JFO 79:421–428. Lockyer et al. 2013. JFWM 4: 242 – 254. Casazza, USGS, unpublished
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Sage-Grouse nest survival declines with increased raven numbers
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Threshold of raven abundance
Coates 2007
~0.4 ravens / km 2
Ravens per transect
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Resp. Covariate Estimate lower upper
Ravens predation increases with less shrub cover
95% CI
• 1% decrease in shrub cover increased the odds of raven predation by 7.5%
• 20–30% sagebrush cover and >40% total shrub cover Coates et al. 2010. JWM 74:240–248.
Raven raven 0.23 0.11 0.41*
shrub cover -0.08 -0.15 -0.02*
grass 0.17 -0.63 0.41
forb 0.16 -0.40 0.70
understory 0.02 -0.04 0.08
shrub height 0.00 -0.06 0.06
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Important Interaction
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Example of Science-based Adaptive Management Strategy
Tier 1 –Maintain or improve
habitat conditions that reduce
predation
Tier 2 – Reduce access to
anthropogenic subsidies
(concurrent with Tier 1 actions)
Tier 3 – Lethal raven removal
(concurrent with Tier 1 and 2 actions)
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Example of Science-based Adaptive Management Strategy
1. Course-scale site selection for targeted management actions
2. Local-scale surveys at selected sites for density estimates
3. Three-tiered management action approach
4. Conduct post management monitoring
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1. Course-scale site selection for targeted management actions
Informing management: Which areas of the state would benefit from raven management actions? Information Products: • State-wide map (course-scale) of raven occurrence map
• State-wide map (course-scale) of raven density
• Impact state-wide maps (prey distribution, raven density,
and raven occurrence)
Example
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Surveyed sites = ~32 Surveys = >15,000 Survey with ravens = >11,000
Preliminary Information—Subject to Revision. Not for Citation or Distribution
1. Course-scale site selection for targeted management actions Example
Preliminary State-wide Raven Occurrence Map
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
• Land cover & vegetation – % Sagebrush, herbaceous, grassland, non-
sagebrush shrubland, annual grasses, shrub height, sagebrush height, pinyon-juniper, forested, riparian, NDVI, wet meadow
• Anthropogenic – Impervious (developed), road density,
transmission lines (low, medium, high), cell and radio towers, agriculture, land ownership, county-level livestock density
• Elevation & Topography – Elevation, topographic roughness, topographic
radiation aspect index, heat load index, compound topographic index, topographic position index
• Habitat edges – open vs. shrub habitat, agriculture vs. shrub
habitat, forested & pj vs. shrub, forested & pj vs. open
• Disturbance – Cumulative burned area (wildfire)
• Hydrology – Streams, springs, water bodies, open water
1. Course-scale site selection for targeted management actions Example
Preliminary State-wide Raven Occurrence Map
Elevation Developed
Vegetation (NDVI) % Herbaceous
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
1. Course-scale site selection for targeted management actions Example
Preliminary State-wide and Great Basin Raven Occurrence Map
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
1. Course-scale site selection for targeted management actions Example
Preliminary State-wide and Great Basin Raven Occurrence Map
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
1. Course-scale site selection for targeted management actions Example
Preliminary State-wide and Great Basin Raven Density Map
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT Sage-grouse Nesting Habitat (Coates et al. 2016)
Index: Raven occurrence x density
DRAFT
1. Course-scale site selection for targeted management actions Example
Preliminary State-wide Impact Map
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Informing management: How to prioritize actions among sites? What is rationale for actions? At specific sites, where to start? Information Product: Develop standardized raven survey protocol
o User-friendly interface to estimate densities annually
across site and state-wide
o User-friendly interface to generate site-specific raven maps and prey potential impact maps
2. Local-scale surveys at selected sites for density estimates
Example
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2. Local-scale surveys at selected sites for density estimates
Example
Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
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Developing models and user-friendly interface for agencies to estimate density with confidence intervals
2. Local-scale surveys at selected sites for density estimates Example
EXAMPLE
Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
~0.53 ravens per km2
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2. Local-scale surveys at selected sites for density estimates
Example
Examples of time-series estimates
DRAFT DRAFT
Preliminary Information—Subject to Revision. Not for Citation or Distribution
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3. Three-tiered management action approach
Informing management: What evidence of potential impacts exist to assign management action? Information Products:
• Predation thresholds for management use (inform tiers)
o Raven density effects
o Overlap between ravens and species of concern
• Scientific findings to inform specific actions
o Movement, space use patterns, and demography
Example
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT Recent Population-level analysis: Sample sizes: • 14 sites
• ~400 sage-
grouse nests
• ~12,000 raven surveys
• 45 site/year nest survival and raven density estimates
3. Three-tiered management action approach
Previous Finding: Effect on sage-grouse nesting in NE Nevada ~0.4 ravens / km 2
Example
Science to Inform Management Actions (Thresholds)
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
Low raven density = increased variation in sage-grouse nest survival
3. Three-tiered management action approach Example
Science to Inform Management Actions (Thresholds)
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
DRAFT
3. Three-tiered management action approach Example
Science to Inform Management Actions (Thresholds)
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EXAMPLE
Preliminary Information—Subject to Revision. Not for Citation or Distribution
Informing Management Tiers (and site-specific actions) Based on: 1) empirical density estimate, confidence limit and intersection with effects threshold 2) intersection with species of concern maps
~0.4 ravens/km 2
DRAFT
3. Three-tiered management action approach Example
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Developing model and user-friendly interface for agencies to develop spatially explicit maps for targeting areas for management actions
Preliminary Information—Subject to Revision. Not for Citation or Distribution
3. Three-tiered management action approach Example
Specific Areas to Target for Management
DRAFT DRAFT
Local Scale Analysis
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Developing model and user-friendly interface for agencies to develop spatially explicit maps for targeting areas for management actions
Preliminary Information—Subject to Revision. Not for Citation or Distribution
3. Three-tiered management action approach Example
Specific Areas to Target for Management
DRAFT DRAFT
Local Scale Analysis
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
Credit: Walter Wehtje
Credit: Walter Wehtje
Breeding Period Non-Breeding Period
GPS Marked Individuals = 10 (objective = 30); Locations = 9,350 • Estimate seasonal utilization distributions for breeding and non-breeding seasons • Relate space use to sage-grouse nesting areas and anthropogenic subsidies
3. Three-tiered management action approach Example
Movement and Space Use Information
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Informing Management: Are management actions beneficial? Is there variation in their effectiveness? When to stop actions? • Continue rapid survey assessment • Modify management actions based outcomes
• Adjust plan to accommodate changes in raven numbers and use • Graduate sites out of action
Preliminary Information—Subject to Revision. Not for Citation or Distribution
4. Conduct post management monitoring Example
Measuring Effectiveness of Actions
Pre-management Post-management
Pre Post
Den
sity
(ra
ven
s /
km 2
)
DRAFT
DRAFT DRAFT
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
4. Conduct post management monitoring Example
Measuring Effectiveness of Actions
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Preliminary Information—Subject to Revision. Not for Citation or Distribution
Preliminary Abundance Estimates of Ravens
Number of Ravens in sagebrush cover types across Great Basin ~145,000 Number in Nevada sage-grouse habitat ~40,000 Number across state ~110,000
Sage-grouse spring habitat
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Next Steps
• Continue to improve state-wide occurrence, density, and impact maps
• Develop user-friendly interface to generate local scale maps and density estimates with survey data
• Incorporate new information on relationships between ravens, habitat and sage-grouse populations
• Incorporate findings using GPS data to inform dispersal, movement patterns, and space use of ravens