Millions of dollars are spent on removing predators from offshore islands in the aim of protecting seabirds and island biodiversity. However, post-eradication monitoring is limited, so our understanding of how and if seabirds and their island habitats recover is also limited. In this paper, we investigated the recovery of seabirds to islands in the Hauraki Gulf, New Zealand to try and contribute to understanding these recovery processes better. The paper was published in the journal Oryx and you can find a PDF here!
Abstract:
Protecting seabirds is a global conservation priority
given that 29% of seabird species are threatened with extinction.
One of the most acute threats to seabirds is the
presence of introduced predators, which depredate seabirds
at all life stages, from eggs to adults. Consequently, eradication
of invasive predators has been identified as an effective
and commonly used approach to seabird conservation.
Seabird recovery following the eradication of predators is influenced
by complex and interacting environmental and
demographic factors, and there are gaps in our understanding
of species-specific responses. We reflect on the recovery
of seabirds on islands cleared of predators, drawing on the
equilibrium theory of island biogeography, and synthesize
key influences on recovery reported in the literature. We
present a regionally specific case study on the recovery of
seabird colonies (n = 98) in the Hauraki Gulf, New
Zealand, which is a hotspot of seabird diversity (27 species),
with a long history of eradications of invasive predators. We
found that on islands cleared of predators seabirds recover
over time, and such islands have more diverse seabird assemblages
than islands that never had predators. Recovery
appears to be influenced by a suite of site- and species-specific
factors. Managers may assume that given enough time
following eradication of predators, seabirds will recolonize
an island. Although time is a factor, proximity to source
populations and human activities has a significant effect
on recolonization by seabirds, as do demographic traits, colonizing
ability and habitat suitability. Therefore, integrating
expected site and species-specific recovery responses in the
planning of eradications should help guide post-eradication
management actions.
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