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How Does Himalayan Blackberry Impact Breeding Bird Diversity?

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

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How Does Himalayan Blackberry Impact Breeding Bird Diversity?

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  1. 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

  2. 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.)

  3. 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?

  4. 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

  5. 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

  6. 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

  7. 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

  8. Jericho Park • Easy access • Large stand-alone blackberry patch • Young forest • Heavily used • Traffic noise • No canopy over blackberries

  9. Jericho Park

  10. Maplewood Flats • Easy access • Good bird diversity • Blackberry in understorey • Potential for transitory migrating species

  11. Maplewood Flats PCS MW004 PCS MW008

  12. Stanley Park • Easy access • On-going IAP management • Heavily used • Narrow patches

  13. Stanley Park PCS SP003 PCS SP004

  14. 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

  15. 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

  16. Study Design N YEWA NWCR AMRO BCCH BCCH BCCH 5 10 15 20 25 30m BCCH SPTO RUHU (♀) MCWA

  17. Results

  18. Analysis • Simpson’s Indices (Reciprocal and Index of Diversity)

  19. 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)

  20. Breeding Period *Confirmed nesting (observed nests/behaviour) Adapted from Bell, K. (undated) and BNA On-line (2010)

  21. 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

  22. 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

  23. 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?

  24. 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

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