How Does Himalayan Blackberry Impact Breeding Bird Diversity?
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How Does Himalayan Blackberry Impact Breeding Bird Diversity? A Case Study of the Lower Mainland of BC Presented to: Invasive Plant Council Research Forum Presented by: Caroline Astley, M.Sc., R.P.Bio., EP October 2011
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How Does Himalayan Blackberry Impact Breeding Bird Diversity?. A Case Study of the Lower Mainland of BC. Presented to: Invasive Plant Council Research Forum Presented by: Caroline Astley, M.Sc., R.P.Bio., EP October 2011. Background. Recognized need for more research - PowerPoint PPT Presentation
Transcript of How Does Himalayan Blackberry Impact Breeding Bird Diversity?
How Does Himalayan Blackberry Impact Breeding Bird Diversity?How Does Himalayan Blackberry Impact Breeding Bird Diversity?A Case Study of the Lower Mainland of BCA Case Study of the Lower Mainland of BC
Presented to: Invasive Plant Council Research Forum
Presented by: Caroline Astley, M.Sc., R.P.Bio., EP
October 2011
Presented to: Invasive Plant Council Research Forum
Presented by: Caroline Astley, M.Sc., R.P.Bio., EP
October 2011
Background
Recognized need for more research Potential for bird habitat, but is it harming
more that it’s providing? What is the real impact, either positive or
negative? Study through Royal Roads Master’s of
Environment and Management Program (MEM - M.Sc.)
Background
Popular opinion: invasives are bad! But how bad are they?
Quantified based on economics Mostly based on obvious changes to native
ecosystems Impacts not measured against baseline
Is it possible to measure the impact they have on biodiversity?
Background
Chose Himalayan blackberry (R. armeniacus) Very visible Contentious Potential for bird and wildlife habitat Aggressively taking over Ubiquitous on landscape
Many don’t know that it’s invasive Socially accepted – berry picking
Himalayan blackberry
Native to Caucasus region
Introduced in 1880’s as cultivated crop
Escaped into PNW by 1945
Common colonizer of disturbed areas
www1.american.edu
Himalayan blackberry
Very aggressive Can produce 7,000 – 13,000 seeds per
square meter that can remain viable for several years
Spreads by root and stem fragments, seeds, and runners
Creates dense thickets
Study
How to determine if there is an impact? Measure biodiversity
Breeding birds easily identified and located Easily replicated Provincial standards exist
Location important Areas where management is active Areas with potential for variety of breeding
birds Mostly urbanized
Jericho Park
Easy access Large stand-
alone blackberry patch
Young forest Heavily used Traffic noise No canopy over
blackberries
Jericho Park
Maplewood Flats
Easy access Good bird
diversity Blackberry in
understorey Potential for
transitory migrating species
Maplewood Flats
PCS MW004
PCS MW008
Stanley Park
Easy access On-going IAP
management Heavily used Narrow patches
Stanley Park
PCS SP003
PCS SP004
Study Design
Followed RISC standards Variable radius point count Five-minute listening periods Ran from April 1 to July 2, 2009
One visit per week minimum Beaufort 2 maximum wind (light breeze) No/light precipitation (drizzle) Min. temp. between 0-7°C Started just after sunrise
Restricted to trails esp. at Maplewood Flats
Study Design
Used Terrestrial Ecosystem Mapping plot cards “Blackberry” plots >80% R. armeniacus
coverage “Control” plots <20% R. armeniacus coverage
Competed RISC “bullseye” data recording sheets
No nest surveys – outside of scope of project
Study Design
N
5 10 15 20 25 30m
BCCH
AMRO
SPTO
YEWA
MCWA
NWCR
BCCH
BCCH
BCCH
RUHU (♀)
Results
Location Jericho Stanley Park Maplewood Flats
Plot Type Blackberry Control Blackberry Control Blackberry Control
Total Ind. 165 281 48 91 141 231
Total Sp. 12 22 11 24 17 28
Analysis
Simpson’s Indices (Reciprocal and Index of Diversity)
Blackberry Control
Reciprocal Index (1/D)
Jericho 6.6291 7.7319
Maplewood 5.861 11.7596
Stanley Park 7.1847 15.1107
Index of Diversity (1-D)
Jericho 0.8492 0.8707
Maplewood 0.8294 0.915
Stanley Park 0.8608 0.9338
What Does It Mean?
Judging by these preliminary results, blackberry has an impact!
Reduction in number of birds and species in blackberry dominated areas
Stand alone thickets are not statistically different from young forest
Some birds are using blackberry Anna’s and Rufous Hummingbird Song Sparrow Spotted Towhee American Robin Fox Sparrow (Possible at Jericho)
Breeding Period
Species Feb March April May June July Aug Sept
AMRO*
SOSP
SPTO
RUHU*
ANHU*
*Confirmed nesting (observed nests/behaviour)
Adapted from Bell, K. (undated) and BNA On-line (2010)
Other Issues
Increased predator access to nests Nest success?
Further study needed
Human disturbance during berry picking Potential shift away from more diverse
food sources
Management Recommendations
Management vs. removal Removal is best for forested ecosystems Replant densely with multiple canopy layers
Thimbleberry Salmonberry Snowberry Black twinberry
Removal during breeding season performed with care
Can leave some behind
Next Steps
Need at least one other season of data collection for rigour
Re-assess study design to remove excess statistical “noise”
Potential future research Why is there an impact? What factors are causing birds to avoid or
select? Is blackberry becoming a preferred forage
species?
Acknowledgements
Dr. David Clements – TWU AY Chapter P.E.O. Field Assistants
BCIT Courtney, Petra, Pascal, and Britta
Hemmera Ashleigh, Barry, Eileen, and Charlie
Hemmera Brian Yates and Scott Weston
