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Appendix D1 Restore Seabirds to San Miguel Island

D1.1 Goals and Nexus to Injury D1-[1](#goals-and-nexus-to-injury)

D1.2 Background D1-[1](#background)

D1.2.1 San Miguel Island and the Introduction of Rats
D1-[2](#san-miguel-island-and-the-introduction-of-rats)

D1.2.2 Seabirds D1-[2](#seabirds)

D1.2.3 Marine Mammals D1-[2](#marine-mammals)

D1.2.4 Endemic Species D1-[3](#endemic-species)

D1.2.5 Project Goals D1-[4](#project-goals)

D1.3 Project Description and Methods
D1-[4](#project-description-and-methods)

D1.3.1 Approach D1-[4](#approach)

D1.3.2 Timing D1-[4](#timing)

D1.3.3 Mitigation Measures D1-[5](#mitigation-measures)

D1.4 Environmental Benefits and Impacts
D1-[6](#environmental-benefits-and-impacts)

D1.4.1 Biological D1-[6](#biological)

D1.4.2 Physical D1-[9](#physical)

D1.4.3 Human Use D1-[10](#human-use)

D1.5 Likelihood of Success/Feasibility
D1-[10](#likelihood-of-successfeasibility)

D1.6 Performance Criteria and Monitoring
D1-[11](#performance-criteria-and-monitoring)

D1.7 Evaluation D1-[12](#evaluation)

D1.8 Budget D1-[12](#budget)

Appendix D1

Restore Seabirds to San Miguel Island

# Restore Seabirds to San Miguel Island

## Goals and Nexus to Injury

This action aims to restore seabird nesting habitat on San Miguel Island
in the Channel Islands National Park by eradicating the introduced black
rat (*Rattus rattus*). Target species for restoration include
burrow/crevice nesting seabirds such as the ashy storm-petrel, Cassin's
auklet, and Xantus's murrelet, as well as other seabirds such as the
western gull, Brandt's cormorant, the pelagic cormorant, and the pigeon
guillemot.

Eggshell thinning and/or elevated levels of DDTs were documented in eggs
of ashy storm-petrels, Cassin's auklets, western gulls, Brandt's
cormorants, pelagic cormorants, pigeon guillemots, and Xantus's
murrelets in the Southern California Bight (SCB) (Kiff 1994, Fry 1994).
Section 5.1.1 provides a detailed description of the seabird nexus to
the injuries of the Montrose case.

## Background

Island ecosystems are critical for the conservation of biodiversity.
They represent about 3 percent of the world's surface, but support
approximately 15 to 20 percent of all birds, reptiles, and plants
(Whittaker 1998). Of the 484 extinctions that have been recorded since
1600, at least 75 percent have been island endemics (World Conservation
Monitoring Centre 1992). Non-native species were implicated in the
majority of these extinctions (Atkinson 1985). Introduced rats alone are
responsible for about 40 to 60 percent of all bird and reptile
extinctions from islands (Howald et al. 2003). Rats have been introduced
onto more than 80 percent of islands worldwide, causing ecosystem-wide
effects on the distribution and abundance of native flora and fauna
(Atkinson 1985), including in the Channel Islands National Park (Collins
1979, Erickson 1990, Erickson and Halvorson 1990).

Seabird life history characteristics make them particularly vulnerable
to increased predation from introduced predators such as rats. For
example, adult Xantus's murrelets sporadically leave their eggs
unattended during the incubation period while they forage at sea. The
unattended eggs are then vulnerable to predation by rats. Most seabirds
are long lived and have high adult survivorship (Russell 1999). Even
small reductions in adult survivorship can cause drastic reductions in
annual population growth and colony persistence (Keitt et al. 2002).
Rats affect multiple life history stages of seabirds and have been known
to significantly reduce or eliminate seabird colonies in ecologically
short periods of time (Kaiser et al. 1997, Atkinson 1985).

Introduced rats have an ecosystem-wide impact on the California Channel
Islands. As documented on nearby Anacapa Island, introduced rats are
known to feed and prey on many floral and faunal organisms, including
terrestrial and intertidal invertebrates, reptiles and amphibians, land
birds, and a wide variety of plant material (Erickson 1990). In
addition, black rats likely contributed to the 20-year extirpation of
the Anacapa deer mouse (*Peromyscus maniculatus anacapae*) from East
Anacapa Island (Collins et al. 1979, Drost, pers. comm., 2000). In 2001
and 2002, the American Trader Trustee Council successfully implemented
the Anacapa Island Restoration Project, eradicating black rats in an
effort to restore seabird populations on the island. Given the similar
goals and biological setting between the two projects, the Anacapa
Island Restoration Project will serve as a successful model for the
proposed effort on San Miguel Island.

### San Miguel Island and the Introduction of Rats

San Miguel Island is the westernmost island of the Channel Islands
National Park and is managed by the National Park Service (NPS). This
island totals 37 square kilometers (km^2^) (14 square miles) in size and
is about 13 km (8 miles) long and 6 km (4 miles) wide. The island is
primarily a plateau of about 150 meters (500 feet) in elevation with two
244-meter (800-foot) rounded hills. San Miguel Island is dominated by
grassland, which covers most of the deeper, stabilized soils on the
island terrace (Hochberg et al. 1979). San Miguel Island has a primitive
campground, miles of hiking trails, and several large beaches.

It is unclear when rats were introduced to San Miguel Island. In the
late 1980s, a small rat population appeared to have been restricted to
the west side of the island along the coast from Harris Point to Tyler
Bight (Erickson and Halvorson 1990). Collins (1979) documented rats
using seabird nesting burrows for denning. Rats have also been
documented on beaches and on the upper terraces of the island (Erickson
and Halvorson 1990**,** Collins 1979). In March and July of 2004, a
survey on San Miguel Island documented that rats are distributed along
shorelines and within canyons on the island, but a more comprehensive
survey is needed to determine the full extent of rat distribution on the
island (IC 2004a). The many dry arroyos and erosion drainages provide
key habitat and travel corridors for rats on the island, allowing rats
to penetrate deep inland and across the island (Howald, pers. comm.,
2004).

### Seabirds

San Miguel Island and its associated islets, Prince Island and Castle
Rock, support regionally important and diverse seabird colonies,
including one-third of the breeding seabirds in the Channel Islands
(Wolf 2002). This area hosts at least 11 species of breeding seabirds,
including significant populations of Brandt's cormorants, ashy
storm-petrels, and Cassin's auklets. Other breeding species include
Leach's storm-petrel, double-crested cormorant, pelagic cormorant,
western gull, pigeon guillemot, and rhinoceros auklet. San Miguel Island
and its associated islets represent the southern range on the west coast
of North America for rhinoceros auklets, tufted puffins, and common
murres. Similarly, this area is the northern end of the range for
Xantus's murrelets and possibly black storm-petrels. Tufted puffins were
recently observed on Prince Island (McChesney et al. 1995), and common
murres were also observed in breeding plumage on Prince Island in 2004
(Whitworth, pers. comm., 2004).

Prince Island and Castle Rock are located 0.8 km (0.5 miles) and 1.2 km
(0.75 miles) from San Miguel Island, respectively. There are currently
no rats on either of these islets. The presence of rats on San Miguel
Island presents a risk to the seabird colonies on Prince Island and
Castle Rock, given their close proximity. It is possible that rats could
disperse to these adjacent islets (e.g., via vegetation rafts or boats)
and threaten these important seabird colonies.

### Marine Mammals

San Miguel Island is the only known place in the world where three
different species of pinnipeds breed and the only area where five
species are found. Breeding species include the California sea lion
(*Zalophus californianus*), northern fur seal (*Callorhinus ursinus*),
and northern elephant seal (*Mirounga angustirostris*). Harbor seals
(*Phoca vitulina*) and Guadalupe fur seals (*Arctocephalus townsendi*)
are also known to visit San Miguel Island.

### Endemic Species

The following endemic species on San Miguel Island are important
considerations in the planning of this action: Channel Island song
sparrow (*Melospiza melodia graminea*), San Miguel Island deer mouse
(*Peromyscus maniculatus*), and San Miguel Island fox (*Urocyon
littoralis littoralis*).

The Channel Island song sparrow is a resident sparrow endemic to the
Channel Islands. This subspecies is considered to include the
now-extirpated populations on San Clemente and Santa Barbara Islands
(Patten 2001), and the formerly classified San Miguel song sparrow
(*M.m. micronyx*).

The island fox (*Urocyon littoralis*) is a very small canid that
inhabits six of the largest Channel Islands. The diminutive island fox
is the largest native carnivore on the Channel Islands. Recent
morphological and genetic studies support the division of the *U.
littoralis* complex into six subspecies that are each limited in range
to a single island, including San Miguel Island (USFWS 2004). The three
most important food items in the diet of the San Miguel Island fox
(*U.l. littoralis*) are deer mice, sea-fig (*Carpobrotus chilensis*),
and insects (Collins and Laughrin 1979). Mice may be especially
important prey during the breeding season because they are large,
energy-rich food items that adult foxes can bring back to their growing
pups (Garcelon et al. 1999).

The San Miguel, Santa Rosa, Santa Cruz, and Santa Catalina Island foxes
have experienced precipitous declines in the last eight years (Coonan et
al. 1998, Coonan et al. 2000, Roemer 1999, Roemer et al. 2001, Timm et
al. 2000). Annual population monitoring documented a substantial decline
in island fox populations on San Miguel Island between 1994 and 1999
(Coonan et al. 1998; Coonan et al. in press). During this time period,
island fox populations dropped from an estimated 450 adults in 1994
(Coonan et al. 1998) to 15 foxes in 1999 (T. Coonan, unpublished data,
as cited in USFWS 2004) as a result of predation by golden eagles
(*Aquila chrysaetos*). Deer mouse densities rose sharply after the
population crash of the island fox since the fox is the primary predator
in the San Miguel Island ecosystem. The USFWS listed the San Miguel
Island fox as an endangered species on March 5, 2004 (USFWS 2004).

In 1999, the NPS captured 14 (4 males and 10 females) of the 15
remaining foxes from San Miguel Island to protect the subspecies from
further losses from predation by golden eagles and to initiate a captive
propagation program. In 2003, the one remaining wild island fox was
brought into captivity. In October 2001, NPS moved half of the captive
foxes into a second breeding facility on the island to minimize the risk
of a catastrophic event (e.g., wildfire or disease). The San Miguel
Island fox captive population increased from 14 to 50 foxes after five
years of captive breeding, and 10 of those foxes were released to the
wild on San Miguel Island in fall 2004 (Coonan, pers. comm., 2005). Full
recovery of the San Miguel subspecies may require annual releases of 10
to 20 foxes for as long as a decade (Coonan 2003).

In 2005, the NPS captive breeding program designed to restore the
endangered island fox to the Northern Channel Islands produced a record
38 pups (NPS 2005). On San Miguel Island, 10 pups were born into
captivity, bringing the total number of foxes in captivity to 49. A
total of 4 new pups were recorded in the wild on San Miguel Island in
2005, thus increasing the total estimated number of foxes in the wild to
14 (NPS 2005).

### Project Goals

The goals of this action are to eradicate the introduced black rat,
increase seabird populations, and prevent future rodent introductions.
Due to the scale and complexity of the action, the NPS, with the
assistance of the Natural Resource Trustees for the Montrose case
(Trustees), will prepare a subsequent Environmental Impact Statement
(EIS) or Environmental Assessment (EA) that will undergo public review
and comment. This subsequent document will detail the specific
methodologies of the action, the expected benefits and impacts, and the
mitigation measures to reduce potential impacts. A general outline of
the action is summarized below.

## Project Description and Methods

### Approach

The use of rodenticides is critical to the successful eradication of
rats from islands. Rats have been successfully removed from over 250
islands worldwide, the vast majority of which have been by the use of
rodenticides (IC 2004b, Veitch and Bell 1990, Buckle and Fenn 1992,
Taylor 1993). Nine rodenticides are registered for use in the United
States. The anticoagulants (such as brodifacoum, warfarin, and
diphacinone) are the only rodenticides that have resulted in complete
eradication on islands. One or more of the anticoagulant rodenticides
will be proposed for use on San Miguel Island. The U.S. Environmental
Protection Agency (EPA) will be consulted to obtain registration of a
rodenticide for rat eradication on San Miguel Island. Factors that will
determine the rodenticide of choice include (1) previous successful use
in island restoration projects, (2) demonstrated ability to eradicate
the rat population, and (3) potential adverse effects on the San Miguel
Island environment. Brodifacoum has been demonstrated to provide the
greatest efficacy against the target species and has been used in the
vast majority of successful island restoration projects, including the
Anacapa Island Restoration Project.

Successful eradication requires the delivery of bait into every
potential rat territory on the island, either by using bait stations
deployed on a grid and/or by aerial broadcast from a helicopter, or, in
some cases, broadcast by hand, or a combination of these techniques.
Trapping rats has proven to be ineffective except on very small islands
(e.g., Moors 1985b). San Miguel Island is within the size range of
successful rat eradications that used bait stations or aerial broadcast.
The specific methodology to be used on San Miguel Island will be
determined by a combination of topography and size, previous successful
uses, and a host of other biological constraints and considerations.

### Timing

The removal of the rats will be timed according to a set of biological
conditions maximizing the probability of eradicating rats and minimizing
the potential impact to the San Miguel Island environment (see below).
Typically, eradication is more likely to be successful if bait is
delivered during the dry season, when there is a food shortage and the
rat population is in decline. The entire island will likely have to be
treated at one time to prevent reinvasion of treated portions of the
island.

### Mitigation Measures

This action will be designed and implemented in a manner that avoids,
minimizes, and mitigates impacts to the natural environment on San
Miguel Island. Measures to avoid and mitigate any impacts from the
action will be developed during the planning phases and will be
addressed in the subsequent EIS or EA. The successful mitigation program
used on Anacapa Island will be considered during the development of a
mitigation program for San Miguel Island. The following mitigation
measures are examples that may be incorporated into the program design:

-   Birds

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-   Color and size bait appropriately to minimize direct consumption by
    seed-eating birds.

-   Use bait that will break down rapidly in the San Miguel Island
    maritime climate.

-   If possible, avoid bait application during bird breeding season and
    peak of land bird migration.

-   Design field transects in a manner that minimizes disturbance to
    seabird roosting habitat.

-   Avoid working for extended periods of time in vicinity of seabird
    roosts.

-   Reduce non‑target poisoning of predatory birds with use of
    techniques such as live capture, holding, and/or translocation.

-   Protect Channel Island song sparrows by captive holding subset of
    the population of birds and releasing them once threat of exposure
    is removed.

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```
-   Marine Mammals

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```
-   Avoid bait application during marine mammal pupping seasons.

-   Design field transects in a manner that minimizes disturbance to
    marine mammal haul outs.

-   Avoid working for extended periods of time in vicinity of rookeries
    and haul outs.

-   Work cautiously and slowly around animals using techniques that
    minimize disturbance.

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```
-   San Miguel Island Deer Mouse

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```
-   Design a comprehensive protection plan for the deer mouse that
    incorporates successful techniques used in the Anacapa Island
    Restoration Project. Strategies to reduce impacts will likely
    include captive holding, as well as breeding mice in facilities on
    San Miguel Island for later release onto the island. Because the
    deer mouse is an important food source for the island fox, it will
    be necessary to protect more mice than would be necessary to
    strictly protect the species.

```{=html}
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```
-   San Miguel Island Fox

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```
-   The presence of the endangered island fox presents a unique
    challenge since there is no precedent for rat eradication from an
    island with an endemic carnivore such as the island fox. An initial
    planning step will be to assemble a team of experts, including
    ecologists, veterinarians, NPS managers, behaviorists,
    toxicologists, and rodent control technicians, to address the
    feasibility of the project in light of the potential impacts of the
    project on the island fox. During this initial step, a comprehensive
    avoidance, minimization, and mitigation program will be developed to
    reduce the potential impacts to the island fox to acceptable levels.

## Environmental Benefits and Impacts

### Biological

#### Benefits

The eradication of rats from San Miguel Island will benefit a variety of
seabirds by increasing the amount of available seabird nesting habitat
and decreasing predation on eggs, chicks, and adults. A reduction in
predation will lead to increased population size and breeding success of
seabirds on San Miguel Island. Small crevice-nesting seabirds, such as
the ashy storm-petrel, Cassin's auklet, and Xantus's murrelet, will
likely benefit from the elimination of a predator that is known to take
eggs, chicks, and adults. Ecological monitoring on Anacapa Island after
bait application has demonstrated an increase in the number of breeding
Xantus's murrelets, and these birds were found in new habitat areas from
which rats had previously excluded them (Howald et al. 2005). Within
four months following bait application, two Cassin's auklet nests were
found with chicks on Anacapa Island. This observation represented the
first recorded nesting of this species on the island (Howald et al.
2005).

Although small burrow-nesting seabirds are particularly vulnerable to
rat predation, larger seabirds have also been predated by rats. Studies
have shown rats to be a source of predation to larger seabird eggs and
chicks, including herring gulls and northern fulmars (Zonfrillo 2000),
as well as Laysan albatrosses (Moors and Atkinson 1984). Therefore,
larger seabirds on San Miguel Island (e.g., western gulls) are also
likely to experience increased reproductive success from the elimination
of rats on the island. Although the presence of the island fox limits
the utility of much of San Miguel Island for seabirds, there are steep
areas of suitable seabird habitat on the island that are accessible to
rats but not to foxes. These areas in particular will benefit from rat
eradication.

Prince Island and Castle Rock are located within less than 1 mile of San
Miguel Island; therefore, the eradication of rats on San Miguel Island
will remove a threat to the regionally significant seabird populations
that nest on these islets. Eliminating this risk of rat introduction to
these islets is an important benefit of the project.

In addition to benefiting seabirds, eradicating rats from San Miguel
Island will likely have ecosystem-wide benefits. Based on the results of
post-application monitoring efforts from Anacapa Island, positive
changes have already been measured in the Anacapa Island deer mouse,
side-blotched lizard, and vegetation. Monitoring results on Anacapa
Island demonstrated a two-fold increase in the survival of juvenile
side-blotched lizards after rat removal (Comendant and Sinervo 2002). As
was observed on Anacapa Island, land birds, lizards, and other species
will likely benefit from the action on San Miguel Island. Because
peregrine falcons consume seabirds on the Channel Islands, they are also
expected to benefit from an increase in their prey base.

In summary, rat eradication on San Miguel Island should result in: (1)
increases in small crevice-nesting seabird populations (such as alcids
and storm-petrels); (2) decreased predation on ground-nesting seabirds
such as western gulls; (3) protection of the important seabird colonies
on Prince Island and Castle Rock from rat invasion; (4) decreased
predation of some terrestrial and marine intertidal invertebrates; and
(5) broad ecological benefits to the San Miguel Island ecosystem.

#### Impacts

To successfully eliminate rats from San Miguel Island, a highly
efficacious rodenticide must be used to ensure complete eradication.
Because there are no rat-specific toxicants, the use of a rodenticide to
eradicate rats will pose a risk of poisoning non-target species on San
Miguel Island. Non-target species are defined as those species that are
unintentionally exposed to the rodenticide. Although non-target
poisoning is likely, the probability of poisoning depends on the
toxicity of and the organism's exposure to the rodenticide.

Non-target poisoning is generally categorized as primary or secondary
poisoning. Primary poisoning occurs when a non-target species consumes
the bait directly. The species most at risk for primary poisoning on San
Miguel Island are the deer mouse (Erickson and Halvorson 1990), song
sparrow and other granivorous birds, and the island fox. Any individual
that feeds on a primarily poisoned organism is at risk of secondary
poisoning (e.g., a bird that feeds on a poisoned rodent). Species most
at risk for secondary poisoning include predatory birds and the island
fox.

Record and Marsh (1988) and Taylor (1993) identified elements involved
in determining whether a rodenticide poses a poisoning hazard to
non-target species: (1) chemical and toxicological properties of the
rodenticide; (2) composition of the bait and how it is applied; (3)
behavior of non-target species at risk; (4) behavior of the target
species both when intoxicated and at death; and (5) local environmental
factors. Each of these variables will be analyzed and presented in the
EIS or EA developed by NPS. Studies will be conducted to evaluate the
potential risk of poisoning non-target species and to develop
appropriate mitigation measures. This action will proceed only if the
risks to non-target species, in particular the endangered island fox and
endemic deer mouse, can be minimized to an acceptable level.

The recent successful rat eradication on Anacapa Island can be used to
predict some of the potential impacts from the proposed action.
Subsequent planning will determine whether the mitigation measures used
on Anacapa Island will be appropriate for use on San Miguel Island. The
presence of the endangered island fox, however, is a unique feature of
the San Miguel Island project that will require a complete analysis of
the feasibility of the project, the potential impacts of the project on
the island fox, and the development of a comprehensive mitigation
program for the island fox.

#### [Birds]{.underline}

During the Anacapa Island Restoration Project, a total of 94 individual
birds are known to have died from the use of brodifacoum, but the impact
had a negligible effect at a population level (Howald et al. 2005). The
presence of the endemic song sparrow on San Miguel Island will require
additional effort to minimize and mitigate exposure risk, such as the
captive holding of a representative population. Although there will
likely be short-term impacts, the elimination of the non-native rats
should directly benefit the sparrow population as a whole in the long
term. On Anacapa Island, land birds such as the song sparrow, house
finch, and Bewick's wren were breeding within six months after the bait
drop (Howald et al. 2005).

Birds that consume live rodents or carcasses will be at risk for
secondary poisoning. The Anacapa Island Restoration Project demonstrated
that the majority of monitored rats died underground after consuming the
rodenticide and were therefore unavailable as food to avian scavengers
after approximately one week (Howald et al. 2005). This is consistent
with other field studies that evaluated the fate of
anticoagulant-poisoned rodents (Taylor and Thomas 1993, Fenn et al.
1987). Nonetheless, western gulls, common ravens, and birds of prey will
still be at risk for secondary exposure. Several measures implemented
successfully on Anacapa Island, such as coloring the bait and timing the
project outside the breeding season, will minimize potential impacts.
Impacts to predatory birds will also be minimized by capturing and
holding those birds until the period of risk is over. Monitoring results
from the Anacapa Island Restoration Project confirm that insectivorous
birds are not likely to experience extensive secondary poisoning by
preying on invertebrates that ingested bait or tertiary poisoning by
preying on invertebrates that fed on poisoned rat or mouse carcasses.

Roosting seabirds may be temporarily disturbed during either an aerial
or bait station operation. However, the operation will be timed to
coincide with seasonal minimums in the number of seabirds and land
birds. Monitoring from the Anacapa Island Restoration Project
demonstrated that seabirds were only temporarily disturbed by the
operation.

#### [Deer Mouse]{.underline}

The presence of the endemic deer mouse poses a biological challenge to
the eradication of rats from San Miguel Island. Because rodenticides are
designed to kill rodents, the bait will be attractive and poisonous to
mice as well as rats. It is anticipated that any deer mouse that is not
in captivity will be killed by the operation. However, deer mice are
prolific breeders and can undergo considerable annual population
fluctuation. Any reductions in the deer mouse population caused by rat
eradication measures would probably not have a significant long‑term
effect on the population as long as an effective population size remains
(Howald, pers. comm., 2004). Therefore, a strategy that removes the
potential for rodenticide exposure to all mice will be necessary for the
long-term protection of this endemic population.

The Anacapa Island Restoration Project clearly demonstrated that rats
can be removed from an island with an endemic rodent. With the
implementation of the mitigation measures and excellent environmental
conditions for release and breeding, mouse densities on Middle Anacapa
Island approximately 6.5 months after release were comparable to
densities measured prior to the rat eradication (Howald et al. 2005).
Application of established methods used on Anacapa Island (e.g., captive
holding/breeding techniques) should effectively mitigate temporary
impacts on the native mouse population of San Miguel Island.

#### [Island Fox]{.underline}

There is no precedent for the eradication of rats from an island with an
endemic carnivore such as the island fox. Any form of anticoagulant bait
application on the island will present a secondary exposure risk to
foxes through the consumption of any dead rodents that may be available.
Because of the high likelihood of exposure to foxes, an effective
mitigation strategy must be implemented to ensure that direct exposure
is avoided. Such a strategy will involve captive holding of foxes for a
period of time. Foxes may also be impacted by the temporary reduction in
available mice following bait application. Strategies to minimize and
mitigate potential short-term and long-term impacts to the foxes (e.g.,
captive holding) will be developed during the preparation of additional
environmental documentation. Also, future consultation with the U.S.
Fish and Wildlife Service (USFWS) under Section 7 of the Endangered
Species Act will ensure that the proposed action does not jeopardize the
survival and recovery of the San Miguel Island fox.

#### [Marine Mammals]{.underline}

Marine mammals hauled out on beaches may be temporarily disturbed during
either an aerial or bait station operation. The operation will minimize
disturbance to marine mammals using the minimization measures outlined
earlier. However, minor disturbances to marine mammals from the
helicopter activity and hand bait application are anticipated.

#### [Erosion]{.underline}

Project implementation and monitoring may result in minor soil erosion
and compaction. However, the benefits of the eradication (including
stopping weed seed dispersal by rats) will offset any potential impacts
from soil erosion. Careful planning and ongoing monitoring will minimize
any negative impacts due to soil erosion and compaction. Procedures for
staff will be implemented to minimize risks of weed seed dispersal.

#### [Summary]{.underline}

The eradication of rats worldwide has documented ecosystem-wide
benefits. In some cases, there have been short-term negative impacts;
however, the impacts have been of short duration, and recoveries of some
species to higher population levels and/or greater productivity than
pre-eradication conditions have been documented (e.g., Towns 1991). In
most cases, wildlife managers have determined that long-term benefits to
island ecosystems with the removal of introduced rats greatly outweigh
the short-term impacts to non-target species. All of the potential
benefits and impacts of this action will be fully evaluated during the
planning phase. Should the subsequent analysis show that this action is
infeasible or that potential impacts are unacceptable, this action would
not be implemented.

### Physical

#### Benefits

There are no known benefits to geology/earth resources, water resources,
oceanographic and coastal processes, air quality, or noise receptors.

#### Impacts

There are no known impacts to geology/earth resources, water resources,
air quality, and noise receptors. Specific measures will be developed
and implemented to ensure that bait does not enter the marine
environment. On Anacapa Island, a small amount of bait entered the water
indirectly from bouncing off of cliffs. Divers documented that the
pellets began to degrade 1.5 hours after the bait drop and became
scattered crumbs at 5 hours after the bait drop (Howald et al. 2005). No
fish or other animals were observed feeding on the bait. No brodifacoum
residues were detected in any of the fish or invertebrate samples that
were collected. In addition, no brodifacoum residues were detected in
water samples taken from the marine environment at either 24 or 48 hours
after the application (Howald et al. 2005). Unlike Anacapa Island, San
Miguel Island does not have steep cliffs; therefore, there are very few
areas where bait would bounce off of cliffs and into the water.

### Human Use

#### Benefits

This action will have no known benefits to cultural, socioeconomic,
aesthetic, or transportation resources.

Because rats pose health and safety hazards (e.g., Pratt et al. 1977)
and can cause destruction to supplies and equipment, the eradication of
rats will benefit visitors and NPS personnel on San Miguel Island.
Although there have been no known rodent-vectored diseases transmitted
to island staff or residents in the recent past, there is potential in
any rodent population for the transmission of disease to humans. Health
and safety standards will be improved at NPS facilities on the island,
and a potential source of disease will be eliminated. The removal of
black rats from San Miguel Island will be expected to have long-term
health, safety, aesthetic, and recreational benefits and will remove a
destructive nuisance to human habitation and use of the island.

#### Impacts

This action will have no known impacts to cultural, aesthetic, or
transportation resources. Cultural resources will be avoided on the
island during the operation.

To minimize potential exposure to visitors, San Miguel Island will be
closed for several days. Recreational activities such as camping and
hiking will not be permitted during that timeframe. However, due to its
distance from the mainland and the annual visitation rate of less than
200 campers each year, the closure of the island will not have a
significant impact on recreational and visitor activities.

With the exception of possible skin irritation caused by contact with
bait by project workers, negative impacts of the rodenticide on humans
is not expected. Project workers will follow proper safety procedures to
avoid contact with the bait.

## Likelihood of Success/Feasibility

The eradication of rats from offshore islands has been successfully
demonstrated worldwide. As of 2002, rats have been removed from more
than 250 islands (IC 2004b). San Miguel is within the size range of
successful eradications using bait stations or aerial broadcast. The
recent successful removal of rats from Anacapa Island demonstrates that
such a project can successfully overcome the complex regulatory and
biological challenges facing these types of restoration projects in the
United States. Although the presence of the endangered San Miguel Island
fox is a significant factor not present on Anacapa Island, the
experience, knowledge, and lessons learned from the Anacapa Island
Restoration Project will be applied to this action. All of the potential
benefits and impacts of this action will be fully evaluated during the
planning phase through additional environmental documentation. Should
the subsequent analysis show that the action is infeasible or that
potential impacts are unacceptable, this action would not be
implemented.

A key factor to the success of the action is the development and
implementation of a plan to prevent the reintroduction of rats to San
Miguel Island. The effort and conservation gains made from the
eradication could be negated with the reintroduction of rodents or other
non-native species. Invasive species, including vertebrates,
invertebrates, weeds, and pathogens can all be transported to the island
inadvertently and have detrimental impacts on breeding seabirds. The
rodent reintroduction prevention plan will be one component of a
comprehensive program designed to prevent many non-native species from
being introduced onto the island. This program will build upon the
rodent reintroduction prevention plan that is being implemented on
Anacapa Island by the NPS. The plan will address rat spill[^1] kits,
quarantine, monitoring, and response actions.

With the use of techniques employed in successful eradication programs
elsewhere and implementation of a comprehensive prevention plan, the
probability of successful eradication of rats on San Miguel Island is
high.

## Performance Criteria and Monitoring

The success of restoration activities on San Miguel Island will be
measured by the complete removal of the rats from the island and
subsequent increases in seabird populations. A long-term monitoring
plan, to be developed and detailed in the subsequent EIS or EA, will
expand on the following proposed research and monitoring actions:

-   Collect baseline data on rat and mouse distribution patterns,
    relative abundance, and habitat use.

-   Use a combination of trapping and ecological indicators to evaluate
    the presence/absence of rats using pre-eradication survey data to
    compare to post eradication data.

-   Conduct mouse/seabird/land bird/fox monitoring before and after the
    bait application to quantify impact and recovery of these
    populations.

-   Test unarmed bait consumption by non-target animals.

-   Monitor the island fox captive breeding program following standard
    guidelines.

-   Monitor populations of native fauna and flora before, during, and
    after bait application to document potential benefits and impacts.

-   Develop long-term monitoring to detect any introductions as early as
    possible, and build the capacity to respond to and eliminate any
    introduction of non-native rodents or other species.

The benefits of rat removal to seabirds that breed and roost on the
island may be evaluated by increase in population number, increase in
habitat availability, and reduced predation. Measuring statistically
meaningful population increases in any seabird species on San Miguel
Island may take years or even decades. However, increased habitat
availability and reduced predation were demonstrated as soon as five
months after the eradication of rats on Anacapa Island. In the absence
of rats, sea cave nest monitoring of Xantus's murrelets demonstrated
high nesting effort and hatching success, no nest depredation, and signs
of an expansion of their nesting range on Anacapa Island (Whitworth et
al. 2003).

Protocols for seabird monitoring in the Channel Islands were developed
in the 1980s. Consequently, the methods for seabird monitoring in the
Channel Islands are well established and standardized. The NPS
periodically monitors seabirds on Prince Island (primarily Cassin's
auklets), and historical information is available. However, currently no
seabird monitoring occurs on San Miguel Island or Castle Rock, and
minimal historical information exists. To evaluate the benefits of the
action, baseline surveys of seabird populations will be conducted before
project implementation.

## Evaluation

The Trustees have evaluated this action against all screening and
evaluation criteria developed to select restoration actions and
concluded that this action is consistent with these selection factors.
The Trustees determined that this type and scale of action will provide
long-term benefits to seabird populations, including small
crevice-nesting seabirds such as the ashy storm-petrel, Cassin's auklet,
and Xantus's murrelet as well as ground-nesting seabirds such as the
western gull. This action will likely also have benefits to peregrine
falcon populations in the Northern Channel Islands and will likely
provide long-term benefits to the ecosystem on San Miguel Island.

Multiple government agencies and experts will be involved in the
development, evaluation, and implementation of the rat eradication
program. Consultation with these agencies is required before
implementation of the rat eradication program. The USFWS will be
consulted regarding potential effects to endangered species under
Section 7 of the Endangered Species Act. Based on the Anacapa Island
Restoration Project, this action will also seek a Migratory Bird Take
Permit from the USFWS to address potential impacts to migratory birds.
The EPA will be consulted to obtain registration of a rodenticide for
rat eradication on San Miguel Island. In addition, a subsequent EIS or
EA will be prepared for public review prior to project implementation.

## Budget

Project management (development, implementation, and monitoring)
\$1,065,000

Project environmental compliance/project management (NPS) \$330,000

Eradication \$513,000

Mitigation (deer mice, birds) \$300,000

Mitigation (fox) TBD

Supplies \$75,000

Equipment \$65,000

Transportation \$75,000

Public outreach \$30,000

**Estimated Total \$2,453,000**

[^1]: A rat spill is the accidental importation of rats to a rat-free
    island.