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