Restoring biodiversity using mammal-free sanctuaries: implications for birds and seed dispersal

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RESTORING BIODIVERSITY USING MAMMAL-FREE SANCTUARIES:

IMPLICATIONS FOR BIRDS AND SEED DISPERSAL

Sara Bombaci

_{and Liba Pejchar}

1_{Colorado State University, @SPBombaci, Sara.Bombaci@colostate.edu,}

https://spbombaci.wordpress.com/

2_{Colorado State University, @TheLibaLab,}

Liba.Pejchar@colostate.edu

Results

Background

Research Questions

Summary

1) Do mammal-free sanctuaries in New Zealand enhance the

diversity of bird communities and the density of native bird species relative to unprotected areas?

2) Do mammal-free sanctuaries in New Zealand enhance

bird-mediated seed dispersal relative to unprotected areas?

Methodology

• New Zealand's mammal-free sanctuaries substantially increase the density of native birds, while also enhancing bird-mediated seed dispersal

• We provide evidence that these sanctuaries, which require a large

investment of conservation funds, are restoring biodiversity and ecosystem processes

• Our findings offer novel insight into the success of a conservation strategy relevant to the many ecosystems threatened by

invasive predators globally

• Islands are global hotspots of biodiversity. They hold 1/5th _{of the}

world’s land species in less than 5% of the earth’s surface area. Many island species face extinction.

• The loss of island fauna may disrupt ecological processes that depend

on animals, e.g. seed dispersal and pollination, exacerbating diversity decline in these biologically rich regions.

• Invasive mammals are the primary cause of extinctions on islands. • In New Zealand, conservation organizations have constructed a

network of ‘mammal-free sanctuaries,’ which exclude invasive

mammals with predator-proof fencing to conserve native birds. Yet, critics have questioned whether sanctuaries effectively conserve

native species and ecosystems, given a lack of evidence on project outcomes. Our research assessed whether sanctuaries are meeting conservation targets and thus represent a good use of limited funds.

Jan-April, 2016-2017* - 3 paired sanctuary and reference study areas:

Erect mammal-proof fence

Eradicate mammals within & monitor reinvasions Restoration & reintroductions

Steps to create a fenced mammal-free sanctuary:

2

1

3

2

1

3

Tawharanui Sanctuary

& McElroy’s Scenic

Reserve

Maungatautari

Sanctuary & Te Tapui

Scenic Reserve

Rotokare

Sanctuary & Tarata

Conservation Area

Positive effect of mammal-free sanctuaries on bird diversity and

densities for most species. Effect = Mean change in density relative

to reference sites.

POSITIVE EFFECT

NO EFFECT*

NEGATIVE

EFFECT

Tui

Tomtit

N. Island Saddleback

Bellbird

Kererū

N. Island Robin

Whitehead

Eurasian Blackbird

Kākāriki

New Zealand Fantail

5 min bird counts Seed traps –

dispersed seeds Foraging observations 0 0.5 1 1 2 3 Mea n for ag ing ra te (m ean no. of for ag ing ev en ts p er 5 min ut e ob ser va tion period) Tī kōuka * *

*indicates significant difference between paired sanctuary and reference site (Wilcoxin Rank Sum Test, α < 0.05)

Sanctuary site Reference site

0 0.1 0.2 0.3 _Kawakawa * * 1 2 3 * * 0 0.2 0.4 0.6 Mahoe * * 0 0.05 0.1 0.15 _Patē Not at site Not at site Not at site 0 0.05 0.1 0.15 Pūriri Not at site Not at site * * 0 0.02 0.04 0.06 0.08 _Tawa Not at site

Study Area (see methodology for reference numbers)

Chaffinch

Grey Warbler

Eastern Rosella

Silvereye

New Zealand

North Island

*95% confidence interval overlaps zero

Mean disper sed seed abunda nce (mean no. of c lea n s eeds in tr ap s) * Tī kōuka *

*indicates significant difference between paired sanctuary and reference site (Wilcoxin Rank Sum Test, α < 0.05)

Kawakawa Pūriri Mahoe

Not at site Not at site * * Tawa

Study Area (see methodology for reference numbers)

Higher foraging rates and higher densities of dispersed seeds in mammal-free sanctuaries for many native plants

Native

Non-native

Frugivore

Sanctuary site Reference site

*Data presented for 2016 only

0 1 2 3 4 0 5 10 15 20 25 0 10 20 30 40 50 * * * * 1 2 3 _{1 2 3} 1 2 3 1 2 3

Who’s dispersing what?

Line thickness = frugivore importance

1 2 3

Pigeonwood _{Supplejack Nīkau}

1 2 3 1 2 3 1 2 3

1 2 3 1 2 3 1 2 3 1 2 3

Compared density and diversity of birds, foraging rates, and densities of bird-dispersed seeds between sanctuary and reference sites.