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Eradication methods on invasive species on islands; is there an effect on seabird populations?
Page 1 of 30 Y3586736
Environment Department
University of York,
University Road,
York YO10 5DD
Acknowledgments
I would like to take this time to thank all of my lecturers in the Environmental
Department for being supportive when I’ve needed. Especially towards the end of the year. I
would also like to thank my Uncle Boris, because without his trust in me, I would not have
been able to write this. And as always, my parents, for still putting me and my brother before
anything else in this World.
Abstract
134 bird species have gone extinct in the last 500 years. 71 have been due to invasive
species.11.8% are marine birds. Due to marine birds breeding on Islands and being ground
nesters, they are more vulnerable. 80% of the world’s invasive species are found on islands.
Islands are open niches for invasive species as there are no natural predators. 20 years ago
eradication methods on these invasive species were developed. This study uses a systematic
review and Meta analyse approach to investigate what these eradication methods have on
seabird populations. Coefficient correlation (r) being the standardized measure.
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Introduction
Birds are the most diverse of the vertebrate family, having twice as many taxa as
mammals and ten times more species that fly (Sekercioglu 2006). Over the last 500 years,
134 species of birds have gone extinct (Bird Life International 1). It is believed that the recent
decline in bird populations is from invasions of non-native species, at least 71 of these
extinctions is due to invasive species (Bird Life International 1). An invasive species is a non-
native animal or plant that has a negative effect on the native species. They occur in
ecosystems that are similar to their natural environment (Howald et al 2007).
IUCN red list has agreed with this and it explains why 5.7% of terrestrial species, 2%
of freshwater species (mostly birds) and 11.8% of marine species (again mostly birds) have
become extinct recently. Out of the 21 recently extinct marine species, 11 of them have been
marine bird species. (Gurevitch and Padilla 2004). Most of the marine birds that have become
extinct, have been native island species. Island birds are more likely to be effected by alien
invasive species because majority of the time island birds have no predators so have not had
to evolve into fleeing when danger is near (Bird Life International 1 and 2).
Of all the invasive species that have become a problem over recent years, rodents
have become the most dangerous (Howald et al 2007). Unlike most other invasive mammals,
rodents are omnivores so can affect all species on the island, plant or animal. 80% of the
world’s major islands have invasive rodents and more are continuously invading the World’s
islands. Island ecosystems may be more prone to invasion because their species faced few
strong competitors and predators, or because their distance from colonizing species
populations makes them more likely to have "open" niches for invasion. Over 20 years ago
systematic techniques were developed into eradicating the invasive rodents due to the
negative impacts that were occurring (Howald et al 2007). Between n 1983 and 1984 the
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WWF poisoned and trapped Rattus rattus (Appendix; Table 2) on Cerro Pajas, Galapogas.
This is because the once abundant, now endangered, dark Pterdroma phaeopugia (Appendix;
Table 1) has been affected by the invasive R.rattus. The rat feeds on the eggs and chicks.
Before the eradication methods began, only 31% of the eggs that were laid fledged. In 1983,
46% fledged (104 nests were checked) and in 1984, 72% fledged (100 nests were checked)
(Cruz and Cruz 1996).
To prevent extinction, eradications have become a very important tool (Howald et al
2007). Howe Scientists believe that the best way to prevent an invasion (defined as when
none native species takes over an island) is to catch the alien species when it first arrives at
the island and has not affected anything on the island yet. This can be achieved when an alien
species has arrived on island but has not bred or taken over is known as incursion. This is the
critical time for the eradication of the alien species (Russel et al 2006). A good example of an
island that has managed to eradicate an invasive alien species problem is the Clipperton
Islands, which is located 1000km South West of Manzanillo, Mexico. Feral pigs were
introduced by settlers at the turn of the Centenary. Before this, the island was a sparsely
vegetated atoll and was home to a high density of plant eating land crabs and 10,000s nesting
marine birds. The pigs would feed on the crabs and the eggs of the nesting marine birds.
Causing a massive decrease in marine birds. It was reported that only 150 Scula dactylatra
and 500 Scula leycogasta (Appendix; Table 1) were now on the island. In 1958, all of the
pigs were shot. By 1968, the breeding pairs of seabird population had increased to 25,000
(Birdlife International 3)
Using a systematic review approach and a Meta analysis on independent and primary
research studies on marine bird species after eradication of invasive species this study will
discuss the impacts invasive mammals are having on island marine birds and how eradication
techniques can help prevent declines in species population or eventual extinction in species.
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Systematic reviews and Meta analysis have been used in health care for a number of
years now, however in recent year’s conservationists and ecologists have been using the
methods. A systematic review is considered the best way to synthesis the findings of several
studies that have investigated the same question. They are defined as an overview of
scientific strategies that limit bias to the regular association, critical assessment and synthesis
of all relevant studies on a specific topic. They are designed to locate, appraise and synthesize
the evidence relating to the same scientific question to provide informative and evidence-
based answers (Cook et al 1995; Dickson et al 2014). This type of review requires the
following to be successful; definition of the question/problem, identification and critical
assessment of the evidence that’s available, synthesis of the findings and finally the drawing
of a relevant conclusion (Dickson et al 2014). A Meta analysis is a quantitative overview of
the systematic review. Statistical methods from primary and independent research are used to
combine and summarize the results of several relevant studies all asking the same question.
(Cook et al 1995).
The aim of this study is to see if the eradication of predatory invasive species on
islands has an effect on the native marine bird populations. This will be achieved by using a
systematic review and a Meta analysis on previous primary and independent studies.
Methods
There are nine steps to follow whilst doing a systematic review (Table 1). Fig 1 shows
these steps as a flow chart, and how many studies were found/removed within reason during
this study. Step 1 is to perform a scoping search to help determine the aim of the project.
Once the aim of the project had been determined the inclusion criteria (Table 3) and search
terms (Table 2) were developed to help with the following steps. Step 2 was achieved by
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using Web of Science (WoS) and Scopus were the search engines used to find the initial
studies of this review (Over 22,000 studies). All of the studies were imported into an endnote
software where the duplicates were removed.
Table 1: - Table showing what the 9 steps are when doing a systematic review (Edited from Dickson et al 2014)
Step 1 Performing scoping searches identifying the aim
Step 2 Literature Searching and removing duplicates
Step 3 Screening titles and abstracts
Step 4 Obtaining studies
Step 5 Selecting full text studies
Step 6 Quality assessment
Step 7 Data extraction
Step 8 Analysis and synthesis
Step 9 Writing up and editing
Once the duplicates had been removed, the inclusion criteria (established from the
aim of the study; Table 3) was used to screen the abstract and titles of each of the remaining
studies (over 10,000 studies), the studies that were not relevant to the aim were then removed.
Successful eradication in this study was defined as the main invasive species of a study being
removed from the island completely and no trace of the invasive species had be seen in over a
year. 41 studies (Appendix; Table 3) remained after steps 1, 2 and 4 (Table 1) had been
completed (Fig 1).
The studies were then obtained for full text screening (Table 1) (Appenndix; Table 3).
Full text screening of the text is the step in which appropriate data needs to be scoped for the
Meta analyse software. The software used in this study was Meta Win 2.0 (Rosenberg et al
2000). 9 studies (Fig 1) had enough data that could be extracted for a quantitative analyse.
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However, some of these studies had different statistical methods or data was written in
different formats. For a summary analyse to be performed, the data needs to be in the same
statistical format. This study required the data to be measured in effect size. An effect size is
an objective and standardized measure of the magnitude of observed effect between two or
more variables. The observed effect for this study is the population changes for marine birds
after successful eradication (Ferguson 2009).
Effect size is ideal to use in a Meta analyse because different variables can be
compared and different statistical data can be extracted and converted depending on the
availability of data within a study. For this study coefficient correlation (r) was the
measurement used for effect size as a correlation between seabird population changes and
successful eradications needs to be established to reach the aim. Using the “effect size
calculator” provided within the meta-win software and inputting the sample size and the
statistical data (Chi-squared or t test) extracted from the 9 studies the data could be convert to
an r value. The studies that did not have enough data, i.e. no sample size or studies that did
not have full eradication of species, were excluded, leaving only 7 studies that could be used
(Fig 1).
Although all of the data was converted to an r value, the data from larger studies still
had skew compared to the smaller studies. Using the Fisher’s r-to-Z transformation, the effect
size was converted to Zr and the effect size variance (Var(Zr)) were worked out for each. The
r value and sample size are the only forms of data that are needed for this conversion. Using
the category method in the summary analyse, Zr and Var(Zr) were used to plot. Category
method was used as it compared all of the variables (Appendix; Table 3) extracted from the 7
studies. The 7 individual authors were also categorised together to show the mean effect size
and to show what the overall effect has shown. For a Meta analyse to be performed, two
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variables need to be present (Rosenburg et al 200). Some of the studies only had one variable,
due to this they were not included within this analyse.
Table 2: - Table showing the entire search terms typed into Web of Science (WoS) and Scopus for the scoping search.
An asterisk (*) searches for a word with different spellings.
Search Terms WoS Scopus
Invasive and egg* and eradication 41 28
Invasive and egg* and human* 443 380
Invasive and egg* and island* 107 97
Invasive and egg* and mammal* 338 56
Invasive and egg* and plant* 579 326
Invasive and egg* and predator* 208 175
Invasive and egg* and rodent* 116 21
Invasive and nest* and eradication 77 66
Invasive and nest* and human* 1262 1199
Invasive and nest* and island* 220 186
Invasive and nest* and mammal* 911 68
Invasive and nest* and plant* 386 226
Invasive and nest* and predator* 148 114
Invasive and nest* and rodent* 144 46
Island* and Eradication and Human* 381 358
Island* and Eradication and Mammal* 598 139
Island* and Eradication and Plant* 301 170
Island* and Eradication and Predator* 196 125
Island* and Eradication and Rodent* 278 185
Marine bird* and Island* and Conservation 645 158
Marine bird* and Island* and Human* 293 114
Marine bird* and Island* and Invasive 42 21
Marine bird* and Island* and Mammal* 637 163
Marine bird* and Island* and Plant* 356 94
Marine bird* and Island* and Predator* 556 154
Marine bird* and Island* and Rodent* 90 22
Sea bird* and Island* and Conservation 632 231
Sea bird* and Island* and Human* 335 168
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Sea bird* and Island* and Invasive 30 20
Sea bird* and Island* and Mammal* 560 141
Sea bird* and Island* and Plant* 391 121
Sea bird* and Island* and Predator* 426 182
Sea bird* and Island* and Rodent* 97 25
Seabird* and Island* and Conservation 871 231
Seabird* and Island* and Human* 342 336
Seabird* and Island* and Invasive 131 124
Seabird* and Island* and Mammal* 626 267
Seabird* and Island* and Plant* 349 208
Seabird* and Island* and Predator* 685 594
Seabird* and Island* and Rodent* 179 130
Total: - 23,141
Table 3: - Table showing all of the inclusion criteria used to cut down the studies found.
Inclusion Criteria
Predators only
Mammals only
Effects to productivity
Effects to clutch size
Only studies with full eradication (defined in text)
Native island birds only
Marine birds only
No plants, diseases or humans
Sample size needed to be present
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Figure 1- Flow chart showing how many studies that were found in the search, how many were left once duplicates had been removed, once studies that weren't within the inclusion criteria, how many were left once the full-text had been assessed for eligibility. The last part of the flow chart is showing how many studies were included in qualitative synthesis and quantitative synthesis. (Diagram is a template from Moher et al 2009)
Studies included in quantitative synthesis
(meta-analysis) (n = 7)
Full-text articles excluded, with reasons
(n =2)
Full-text articles assessed for eligibility
(n = 9)
Records excluded (n = 10,764)
Records screened (n = 41)
(Appendix; Table 3)
Records after duplicates removed (n = 10,805)
Identification
Eligibility
Included
Screening
Records identified through database searching
(n = 23,141)
Results and Discussion
As stated before the effect size in this study is the observation in population changes
for marine birds after eradication of invasive species. If the effect size is at 0, no effect has
been seen and if the value is a negative number, then a negative effect size has been see
(Rosenburg et al 2000). All of the variables found in this study have a positive effect size
(Table 4), which shows successful eradication of invasive species has a positive effect on
marine bird populations. Fig 2 is a funnel plot showing the positive effect observed for 5
variables. It also shows the larger the effect size, the more of the total variance the effect
accounts for.
Chick mortality (Zr = 0.46; df = 2; CI = 0.29 to 0.63) (Table 4) and breeding success
(Zr = 0.53; df = 20; CI = 0.49 to 0.48) (Table 4) are strongly related to eradication of invasive
predators and showed to be significant (p < 0.05). Predation, egg-stage survival and nest
failure all have a small but positive effect size (Fig 2), it shows that eradication has a positive
effect on these variables but other factors could still be affecting them. Predation and egg
stage survival do not show to be significant (p < 0.05; CI = -0.36 to 0.49; -0.06 to 0.28;
respectfully).
In this study, predation is defined as chick, egg or adult predation that has occurred
after eradication of the main invasive species that has been defined as fully eradicated from
the island. Fig 2 shows predation on the marine birds has a slight positive (Zr = 0.06; Table
4) effect even after successful eradication has been achieved. Some studies stated that there
were more than one predator present on the island and no or failed attempts of eradication
had occurred for them (Appendix; Table 3).
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Table 4: - Table showing the number of studies for 5 different variables measured to represent how seabird populations change after eradication of invasive species, the effect size of these studies, the degrees of freedom and the 95% confidence interval. Table also shows the mean effect size and confidence interval.
Class Number of Studies
Effect Size (zr)
Degrees of Freedom (df)
95% Confidence Interval (CI)
Breeding Success
21 0.53 20 0.49 to 0.58
Egg-Stage Survival
3 0.11 2 -0.06 to 0.28
Nest Failure 3 0.18 2 0.04 to 0.32Predation 2 0.06 1 -0.36 to 0.49
Chick Mortality
3 0.46 2 0.29 to 0.63
Mean 0.33 0.30 to 0.36
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Although there is a positive effect of the removal of the invasive species on nest
failure (Zr = 0.18; Table 4), other factors can affect marine birds’ nests and how successful
they are at breeding. Where marine birds select to have their nests has a correlation with
failure. Marine birds that nest in burrows select appropriate nesting sites on soil and thermal
properties which are going to give them the least chance of nest failure and the best chance of
breeding success. Soil depth is the most important factor for a successful burrow, as it keeps
the nest warm allowing both parents to leave the egg or chick to feed (Buxton et al 2015).
Studies have shown that because of direct consumption by the invasive species there is a
negative effect on the island ecosystems (Caut et al 2005; Le Corre et al 2015). Rattus spp are
particularly damaging on the islands environment because they are opportunistic feeders, they
will feed on the vegetation with or without marine birds breeding on the island. They
continue to feed on vegetation until that vegetation is no longer available and move on (Caut
et al 2005). Fig 3 shows that even after eradication of an invasive species the islands
ecosystem takes at least 15 years to recover (Jones et al 2010, Kappas and Jones 2015). As
soil depth is an important factor in nest and breeding success and islands ecosystems take
time to recover, this could explain why nest failure has a small effect size compared to
breeding success and chick mortality (Buxton et al 2015; Kappas and Jones 2014).
Chick mortality shows to have a high correlation with eradication (Z = 0.46) (Fig 2;
Table 4). However in 2008, Hughes et al found that Onychoprion fustcata populations
(Appendix; table 1) increased after successful eradication in 2003 of Felis silvestris on
Ascension Island (Appendix; table 2), but high chick mortality still occurred due to starvation
and Rattus spp predation. With F.silvestris successfully eradicated Rattus spp have become
the top predator on the island. The rodents were not observed at predating on chicks until
after the eradication of F.silvestris had occurred.
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Table 5: - Table showing three individual studies of the same island at different years after successful eradication in 2002 and how it was observed to effect the native bird and what variable it affected – Full table 3 in Appendix
Author Island Invasive Spp
Native Spp Variable Observation
Jones et al 2005
Anacapa Island
R. rattus Synthliboramphus hypoleucus
Predation 97% of chicks survived
Whitworth et al2005
Anacapa Island
Rattusrattus
S. hypolecucus Nest Site Selection
Increased from 36% to 51% in 2
yearsHatching Success
Increased from 42% to 80% in 2
yearsPredation Decreased from
52% to 7% in 2 years
Whitworth et al 2013
Anacapa Island
Felis catus
Rattus spp
Synthliboramphus scrippsi
S. hypolecucus
Hatching Success
First 8 years had a gradually increase
Anacapa Island (11 miles off the coast of California) has steep, lava rock cliff holds
numerous crevices that are particular important for breeding marine birds. These marine birds
ave become increasingly rare due to invasive species (R. rattus and F. catus) since the 1940s.
40% of Synthliboramphus scrippsi (Appendix, Table 1) nests showed signs of Rattus spp
predation. In the mid 1990s conservation groups looked into how these invasive species could
be eradicated from the island. In 2001, the eradication methods started, by autumn 2002 the
eradication methods had been successful (Whitworth et al 2009). Since then the marine bird
colonies have been monitored (Table 5 – Full table found in Appendix; Table 3). After the
eradication predation on Synthliboramphus hypoleucus eggs and chicks took 2 years to
decrease from 52% of eggs and chicks, to only 7% of the juvenile populations being predated
on (Whitworth et al 2005). Predation still occurred on the island as only R. spp had been fully
eradicated, F. catus numbers had decreased but were still observed on the island.
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Due to this decrease in predation, hatching success increased from 43% to 80% over
the same 2 years and 95% of these hatchlings successfully fledged the nest (Whitworth et al
2005, Jones et al 2005). However, frequency of nests observed did not increase as rapidly as
these variables. There was only a 15% increase in frequency of nests found on the island
(Whitworth et al 2005). In 2013, Whitworth et al observed the same gradually incline in
marine bird species as discussed previously (Fig 3). They observed that in the first 8 years
after the successful eradication of R. spp there was a gradually increase in the marine bird
populations and nests. However in the first 2 years a higher percentage of chicks survived to
fledging due to the lack of predation.
These studies show that eradication methods do have a positive effect on marine
bird’s chicks and eggs in the first stages after eradication as there is less predation but over
time has a positive effect on the breeding population.
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Figure 2: - Forrest Plot showing each variable plotted using its effect size (Zr - FIsher Z-Test) and it's error bars (N = How many studies were included in the Forrest Plot).
During this study, limitations were met, the main whilst extracting the data for
analyse being that not all studies write the results into the same format or provide sufficient
data (i.e. sample size or statistical analyse) to convert. Due to this, more studies were used in
a qualitative manner than a quantitative (Appendix; Table 3), although both show that there is
a positive effect to seabird populations after successful eradication methods of invasive
species.
Another limitation whilst looking through studies for available data, was that although
some of the studies used the same variables, they were described in a different matter. Cooper
et al (1995) defined breeding success as the percentage of burrows that were still occupied at
the end of breeding season, whereas Ratcliffe et al 2010 defines breeding success as the mean
percentage of hatchlings that fledged successfully. Some of the studies with multiple variable
measurements also stated that there were more than one invasive species on the island,
however that made it clear if these species were still present and what effect they were having
on the native species. Due to this, those studies were removed from this study as this was not
classed as a full eradication.
Although these limitations were met, all of the studies showed that the successful
eradication of invasive species from islands had a positive effect on the native seabird
populations. Although there is a positive effect, they do not recover immediately. In 2014
Kappas and Jones theorised that seabird populations would need to recover passively and
actively for the islands ecosystem to restore itself (Fig 3).
The aim of this study was to see if the eradication of predatory invasive species on
islands has an effect on the native seabird populations by conducting a Meta analyse on
primary and independent studies. The mean effect size of all 7 studies was 0.53, this showed
to be significant (p < 0.05; Mean CI = 0.49 to 0.58). This shows that there is an overall
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positive effect on seabird populations after invasive species have been eradicated from the
island. In Meta win, a fail-safe analyse was performed in order to see how many unpublished
studies would need to be out there in order to invalidate the conclusions drawn about the
overall significance of the results. This was analysed using Rosenthal’s method. 12486
(variable analyse) and 7999 (individual studies) unpublished studies are unlikely, further
showing the overall significance of these results is valid (Rosenberg et al 2000) and the aim
of the study has been met.
Figure 3: Theoretical trajectories island ecosystems could take following eradication. 1. Solid line shows island conditions improve to pre-invasion conditions passively. 2. Hatched line shows islands are locked into a degraded state until seabird restoration is initiated after which the systems recover. 3. Box shows the island does not recover passively and since no furhter restorationis initiated is remains in a invasive species free but degraded state. (Kappas and Jones 2014)
WORD COUNT = 3120
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Disclaimer
The views in this dissertation are those of the others and do not reflect in anyway of
studies used or the opinions of the University of York
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33) Masuda, B. M. and I. G. Jamieson (2013). Response of a reintroduced bird population to a rat reinvasion and eradication. New Zealand Journal of Ecology 37(2) 224-231.
34) Matias, R. and P. Catry (2008). The diet of feral cats at New Island, Falkland Islands, and impact on breeding marine birds. Polar Biology 31(5) 609-616.
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35) Medina, F. M., et al. (2011). A global review of the impacts of invasive cats on island endangered vertebrates. Global Change Biology 17(11) 3503-3510.
36) Meek, P. D., et al. (2011). Eradication of Black Rats Rattus rattus L. from Bowen Island, Jervis Bay NSW. Australian Zoologist 35(3) 560-568.
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38) Olivera, P., et al. (2010). Successful eradication of the European rabbit (Oryctolagus cuniculus) and house mouse (Mus musculus) from the island of Selvagem Grande (Macaronesian archipelago), in the Eastern Atlantic. Integrative Zoology 5(1) 70-83.
39) Oppel, S., et al. (2014). Habitat-specific effectiveness of feral cat control for the conservation of an endemic ground-nesting bird species. Journal of Applied Ecology 51(5) 1246-1254.
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Appendix
Page 23 of 30Y3586736
Table 1: - List of Latin names and common names of marine birds
Latin Names Common NamesPterdroma phaeopugia Dark Rumped Petrel Scula dactylatra Masked BoobyScula leycogasta Brown BoobySynthliboramphus hypolecucus
Guadalupe murrelet
Synthliboramphus scrippsi Scripps’s murreletOnychoprion fustcata Sooty terns
Table 2: - List of Latin names and common names of invasive predators
Latin Names Common NamesRattus rattus Black rat
Felis silvestris / catus Feral cat
Acridotheres tristis Common Mynas
Table 3: - Table showing the 41 studies that were full text screened for data. (NB = what results the study found without showing with statistics, S = Statistical analysis used, U = studies included in this study, Y = Included/Yes, N = Not included/No, S.s = If sample size was stated in the study or not, S.E = If the invasive species was fully eradicated from the island or not)
AuthorYear
Island Invasive Species
S.E
Native Species
Variable S.s
S NB U
Algar et al
(2011)
Rottnest Felis catus
Y Mammal Breeding Population
N N Increase in population
N
Bolton et al
(2014)
Steeple Jason
Grand Jason
M.musculus
N Garrodia nereis
Oceanites oceanicus
Predation N N High rates of egg and chick loss.
N
Bourgeois et al
(2013)
Zembra Rattus rattus
Y Puffinus yelkonan
Breeding Population
N N Increase in population
N
Brodier et al
(2011)
Kerguelen
Archipelago
Oryctolagus
cuniculus
Y Halobaena caerulea
Pachyptila desolata
Pelecanides georgicus
Breeding Population
N Y Increase in population
N
Buxton et 92 None Y 132 Species Breeding N Y - Increase in N
Page 24 of 30Y3586736
al(2014)
Specified Population Models
population
Buxton et al
(2015)
5 New Zealand
Rattus exulans
Y Pterodroma macroptera
Puffinus gavia
Puffinus carneipes
Puffinus assimilis
Pelecanides urinatrix
Puffins griseus
Pterodroma pycrofti
Nest Site Selection
N N A distinct patternof high
nestdensities
afterrat
eradicationMore chicks
Ringed.
N
Capizzi et al
(2010)
Italian R.rattus Y Calonectris diomedea
P.yelkonan
Breeding Pairs
N Y Increase in breeding
pairs
N
Caut et al (2008)
Surprise R.rattus Y Sula leucogaster
Sula dactylatra
Puffinus pacificus
Predation Y N 20% of eggs and chicks were
predated on
NRattus
Norvegicus
Y
R.exulans YMus
musculusN
Cooper et al
(1995)
Marion Felis silvestris
Y P.macroptera
Procellaria aequinctialis
H.caerulea
Breeding Success
Y Y See text for more details
Y
Girardet et al
(2001)
Little Barrier
F.silvestris
Y 14 species Bird Population
N N 3 species had
increased, 2 species
had decreased
and 9 N
changes
N
R.exulans N
Hervias et al
(2013)
Corvo Rattus spp
Y C.diomedea Breeding Success
Y N Low breeding Success,
F.silvertus most
N
Mus domesticu
s
N
Page 25 of 30Y3586736
destructiveFelis catus
Y
Howald et al
(2010)
Anacapa R.rattus Y S.hypolecus None N N Eradication proved
positive in other
areas, this study had a
theory it would
improve here too
Hughes et al
(2008)
Ascension
F.silvestris
Y Onychoprion fustcata
Breeding Success
Incubation Success
Egg-Stage Survival
Nest Failure
Predation
Y Y See text for more details
Y
R.rattus NAcridoth-eres tristis
N
Breeding Population
N N Population Increased over time
N
Igual et al(2008)
Congreso R.rattus Y C.diomedea Breeding Success
Egg-Stage Survival
Chick Mortality
Y Y See text for more details
Y
Imber et al
(2000)
Whale - 2
colonies
R.rattus Y P.macroptera
Breeding Success
Y Y See text for more details
Y
Jones et al
(2005)
Anacapa R.rattus Y Synthliboramphus
hypoleucus
Predation N Y Predation reduced
and 97%of chicks
survived
N
Jones et al
(2010)
15 New Zealand
Rattus exulans
N None Soil, plant and spider
ratio
N N No recovery
for 15 years and then
rapid recovery
N
Jouventin et al
Crozet R.rattus Y P.aequinoctialis
Breeding Success
Y Y See text for more
Y
Page 26 of 30Y3586736
(2003)Nest
Failure
details
Kappes and Jones
(2014)
None specified
None specified
N Fractercula arctica
Breeding Pairs
N N Took 27 years
to reach 100 pairs
N
Kazuto et al
(2010)
Bonin , Japan
R.rattus Y Bulweria bulwerii
Predation N Y No local extinction
due to prompt
eradication
N
Latorre et al
(2013)
Mediterranean
R.rattus N Gulls Egg predation
N N Rats predate on
all sized eggs
N
Lavers et al
(2010)
None specified
None Specified
Y Birds Bird Population
N Y On average all populations increase by 25.3%
N
Le Corre et al
(2015)
Tromelin R.Norvegicus
Y S.dactylatra
Sula sula
Breeding Pairs
N Y Slow increase
then rapid
increase after 8
years of eradication
of R.rattus
N
M.musculus
N
Marie et al
(2014)
Moku'auia
R.rattus N P.pacificus Breeding Population
N Y Chicks were
higher in years
with N
predators (3,127)
than years with
predators (1,275)
N
Masuda and
Jamieson(2013)
New Zealand
Rattus spp
N Terrestrial Bird
Breeding Success
N N 31.5% decline in 12
months
N
Matias and Catry
(2008)
New , Falkland
F.catus N P.aequiNctialis
Breeding Success
Y Y 2005 breeding success -
48%. 2006
breeding success -
N
Page 27 of 30Y3586736
44%Meek et
al(2001)
Bowen R.rattus Y Burrowing Marine birds
Predation N N R.rattus were
observed feeding at the
seabird burrows before
eradication
N
Medina et al
(2011)
120 F.silvestris
N/A
123 Birds IUCN Red List
N N 14% of global
extinctions is
due to cats and
threat 8% of birds
N
Olivera et al
(2010)
Great Salvage
M.musculus
O.cuniculus
Y C.diomedea
B.bulweria
Puffinus assimilis
Pelagodroma marina
Oceanodroma castro
Breeding Population
N N N
Oppel et al
(2014)
St Helena
F.catus N Charadrius sanctaehelen
ae
Nest Survival
N N Eradication had
a positive effect
on nest survival
N
Ratcliffe et al
(2010)
Ascension
F.silvestris
N S.dactylatra
F.aquila
Breeding Success
N Y Less adult carcasses found - 4,500
per year to negligible
levels
N
Ringer et al
(2015)
Europa
Juan de Nva
R.rattus Y Phaethon rubricasuda
Breeding Success
Predation
Y Y See text for more details
Y
Robinson and
Copson (2014)
Macquarie
F.catus Y Procellaria cinerea
Breeding Population
N N Not been recorded breeding
on the for 100 years but returned
N
Page 28 of 30Y3586736
after eradication
Russel and
Holmes(2015)
Tropical Rattus spp
Y None Populations N N Few decades to recover
populations
N
Tabak et al
(2015)
Falkland R.norvegicus
Y Terrestrial Bird
Relative abundance
N N Abundances were lower on with rats
than those
without
N
Vanderwerf et al(2014)
Kaena Point,
Hawaii
Canis familiaris
F.cattus
Herpestes auropunc
tatus
Rattus spp
Y Puffins pacificus
Populations N N Maps showing satellite
images of population
s growing over time
N
Wanless et al
(2012)
Gough M.musculus
N Pterodroma incerta
Nest Survival
N Y In 2007, only one
chick fledge
Successfully
N
Whitworth et al(2005)
Anacapa R.rattus Y S.hypolecus Nest Site Selection
N N Increased from
36% to 51% in 2
years
N
Hatching Success
N N Increased from 42%to 80% in
2 years
N
Predation N N Decreased from
52% to 7% in 2 years
N
Whitworth et al (2013)
Anacapa F.catus
Rattus spp
Y Synthliboramphus scrippsi
Hatching Success
N N After 8 years,
success rate
gradually increased
N
Wiles(2003)
Guam, Mariana
None Specified
Y 27 marine birds
Breeding Population
N N Decrease in
populations have
N
Page 29 of 30Y3586736
prompted conservati
on actsZino et al
(2008)Selvage
m Grande
O.cuniculus
Y C.diomedea Breeding Success
Y Y See text for more details
Y
M.musculus
N N Y 23% more successful fledglings
5 years after
eradication
N
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