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D3. Restore Seabirds to San Nicolas Island
[3-1](#restore-seabirds-on-san-nicolas-island)

D3.1 Goals and Nexus to Injury [3-1](#goals-and-nexus-to-injury)

D3.2 Background [3-1](#background)

D3.2.1 San Nicolas Island [3-1](#san-nicolas-island)

D3.2.2 Fauna on San Nicolas Island [3-1](#fauna-on-san-nicolas-island)

D3.2.3 Brandt's Cormorant [3-2](#brandts-cormorant)

D3.2.4 Western Gulls [3-2](#western-gulls)

D3.2.5 San Nicolas Island Fox [3-2](#san-nicolas-island-fox)

D3.2.6 Presence and Impacts of Feral Cats on San Nicolas Island
[3-2](#presence-and-impacts-of-feral-cats-on-san-nicolas-island)

D3.3 Project Description and Methods
[3-3](#project-description-and-methods)

D3.4 Environmental Benefits and Impacts
[3-3](#environmental-benefits-and-impacts)

D3.4.1 Biological [3-3](#biological)

D3.4.2 Physical [3-4](#physical)

D3.4.3 Human Use [3-4](#human-use)

D3.5 Likelihood of Success/Feasibility
[3-5](#likelihood-of-successfeasibility)

D3.6 Performance Criteria and Monitoring
[3-5](#performance-criteria-and-monitoring)

D3.7 Evaluation [3-5](#evaluation)

D3.8 Budget [3-6](#budget)

Appendix D3

Restore Seabirds to San Nicolas Island

# Restore Seabirds on San Nicolas Island

## Goals and Nexus to Injury

The goal of this action is to restore western gull and Brandt's
cormorant colonies on San Nicolas Island by eradicating feral cats.
Eggshell thinning and/or elevated levels of DDTs were documented in eggs
of the western gull and Brandt's cormorant in the Southern California
Bight (SCB) (Kiff 1994, Fry 1994). Section 5.1.1 provides a detailed
description of seabird nexus.

## Background

Introduced predators, in particular feral cats and rats, are one of the
greatest threats to seabird populations on islands (Moors et al. 1992,
Whittaker 1998). On islands worldwide, feral cats are directly
responsible for a number of extinctions and extirpations across multiple
taxa (Iverson 1978, Moors 1985b, Kirkpatrick and Rauzon 1986, Cruz and
Cruz 1987, Towns et al. 1990, Donlan et al. 2000, Veitch 2001). Cats are
opportunistic hunters and consume a wide variety of mammals, reptiles,
birds, and insects (Kirkpatrick and Rauzon 1986, Konecny 1987,
Fitzgerald 1988, Fitzgerald and Turner 2000). Predation by feral cats is
responsible for the extinction of at least 33 bird species (Lever 1994),
including the Stephen Island wren (*Traversia lyalli*, New Zealand),
Socorro dove (*Zenaida graysoni*, Mexico), and Guadalupe storm-petrel
(*Oceanodrama macrodactyla,* Mexico). Cats have also led to local
extirpations of seabird colonies on the Channel Islands, including the
Cassin's auklet from Santa Barbara Island (Willet in Hunt et al. 1979).

### San Nicolas Island

The U.S. Navy--owned island of San Nicolas is one of four southern
Channel Islands, and totals 58 square kilometers (km^2^) (22 square
miles \[mi^2^\]) in size. The island is about 15 kilometers (km) (9
miles) long and 6 km (3.6 miles) wide. The highest elevation is 277
meters (908 feet). In general, the island exhibits sparse vegetation
that is mostly attributable to past sheep ranching, the island's arid
climate, and high winds.

San Nicolas Island provides missile and aircraft launch facilities and
radar tracking in support of the Navy's mission. Infrastructure on the
island includes an asphalt runway, water wells, a desalination plant,
water distribution and sewage systems, roads, telecommunication
facilities, and buildings. Approximately 200 people work and live on the
island. There is no public access to the island primarily due to
security and safety requirements.

### Fauna on San Nicolas Island

San Nicolas Island supports a number of species endemic either to the
Channel Islands or the island itself, including at least 20 plant
species, 25 invertebrates, 1 reptile, 2 birds, and 2 mammals (U.S. Navy
2003). State and federal threatened and endangered species on the island
include the threatened western snowy plover (*Charadrius alexandrinus
nivosus*), threatened island night lizard (*Xantusia riversiana
riversiana*), endangered California brown pelican, and threatened San
Nicolas island fox (*Urocyon littoralis dickeyi*). San Nicolas Island
also supports important marine mammal rookeries, as well as breeding
colonies of Brandt's cormorants and western gulls.

### Brandt's Cormorant

Historical records have shown that Brandt's cormorants have nested on
San Nicolas Island since at least the late 1800s (McChesney 1997). Most
documented nesting occurred at the west end of the island. Prior to the
mid-1970s, a total of 600 to 800 pairs were estimated to breed on the
island (McChesney 1997). This population subsequently declined in the
mid-1970s to only 100 to 200 pairs. This decline is consistent with the
widespread failure of cormorant nests throughout the SCB due to DDT
contamination (Gress et al. 1973). The Brandt's cormorant colony then
underwent dramatic increases from the late 1970s to the early 1990s. In
1991, San Nicolas Island supported the second largest Brandt's cormorant
colony in the Channel Islands, with 5,089 breeding individuals (Carter
et al. 1992). Between 1991 and 1995, the population on San Nicolas
Island varied annually due to a variety of factors including human
disturbance, El Niño conditions, and predation by the island fox. Annual
aerial surveys since 1996 have documented that the Brandt's cormorant
population has expanded and shifted into intertidal environments.

### Western Gulls

Historically, San Nicolas Island supported one of the largest western
gull colonies in Southern California. A large western gull colony was
first documented in 1991 and was estimated at 6,038 breeding individuals
(Carter et al. 1992). However, more recent surveys have documented a
decline in the western gull colony (Smith, pers. comm., 2004). Western
gulls have become more distributed across the island, perhaps due to the
increases in sea lion disturbance at the main colony site and predation
by island foxes. Because western gulls nest on the ground, they are
particularly susceptible to predation.

### San Nicolas Island Fox

The San Nicolas Island fox population has remained stable and is
estimated at 614 individuals (USFWS 2004). This species is listed as
threatened by the State of California. The U.S. Fish and Wildlife
Service (USFWS) recently determined that the federal listing of the San
Nicolas population of the island fox was not warranted under the
Endangered Species Act (USFWS 2004). However, its small population size,
insular nature, lack of resistance to canine distemper and other
diseases, high densities, and low genetic variability increase the
vulnerability of this subspecies (USFWS 2004).

San Nicolas Island foxes are omnivorous, foraging on insects,
vegetation, mice, and seasonally available bird eggs. Predation by the
island fox has caused nesting failure and abandonment of both Brandt's
cormorant and western gull colonies on the island (McChesney 1997). The
San Nicolas Island fox population is negatively affected both by
competition with feral cats and impacts from humans.

### Presence and Impacts of Feral Cats on San Nicolas Island

Cats were first introduced to San Nicolas Island during the 1800s and
later by Navy personnel. Negative impacts from feral cats on the
island's fauna have been documented. Humboldt State University studies
from 1992 to 1996 documented impacts to nesting Brandt's cormorant and
western gulls from feral cats (McChesney 1997, Carter, pers. comm.,
2004). As described in the Navy's 2003 Integrated Natural Resources
Management Plan (INRMP) for San Nicolas Island:

> Feral cats have long been established on San Nicolas Island and pose a
> serious risk to the integrity of the entire ecosystem. Cats are
> implicated in the decline of small animal and bird populations
> worldwide and have especially devastating impacts on closed island
> systems. Cats have detrimental impacts on San Nicolas Island land bird
> populations, seabird colonies, and prey upon the federally listed
> island night lizard and the western snowy plover. Cats directly impact
> the San Nicolas Island fox through competition for prey and indirectly
> through spatial displacement.

In an effort to protect endangered species and sensitive seabird
colonies, the Navy has funded intermittent efforts to control feral cats
since the 1980s. The INRMP identifies the continued control/removal of
cats as a recommended guideline to protect the western snowy plover,
island night lizard, resident and migratory birds, island fox, and
island deer mouse. In addition, Navy personnel are prohibited from
bringing pets onto the island (U.S. Navy 2003).

## Project Description and Methods

The goal of this action is to eradicate feral cats and increase seabird
colonies on San Nicolas Island. This action will expand the ongoing
control efforts by the Navy with the goal of eradicating cats from the
island over an approximate three-year time frame. Proven techniques
(e.g., trapping) used worldwide in recent cat removal programs will be
employed as part of this action. However, given the overlap between cats
and island foxes in terms of size and diet, the methods selected to
eradicate cats will be given careful consideration to avoid impacts to
the fox. This action will explore various techniques for eradication,
but will use methods that pose the least risk to the island fox.

The specific methodologies for this action will be developed and
evaluated in future additional environmental documentation prepared
pursuant to the National Environmental Policy Act (NEPA) and/or the
California Environmental Quality Act (CEQA) in coordination with the
U.S. Navy.

## Environmental Benefits and Impacts

### Biological

Benefits

Eradication of cats from San Nicolas Island will provide long-term
conservation benefits for Brandt's cormorants and western gulls by
removing a non-native predator from the island ecosystem. The Natural
Resource Trustees for the Montrose case (Trustees) anticipate that this
action will result in increased reproductive success for these species
and therefore expansion of these colonies. Both of these species are
endemic to the west coast of North America and have limited ranges. The
colonies on San Nicolas are located within the center of their range and
have historically supported large colonies. This action will contribute
to the protection of these colonies, though they will still be subject
to predation by the native island fox. However, it is anticipated that
larger, more robust colonies will more effectively withstand the ongoing
predation pressure from the island fox.

In addition to seabirds, this action will also have collateral benefits
to the island ecosystem. Sensitive species such as the island fox,
endemic deer mouse, threatened island night lizard, and threatened snowy
plover will likely benefit from reduced predation and competition. This
action will also likely benefit both resident and migratory land birds
on San Nicolas Island because of the removal of this non-native
predator. The Navy's INRMP identifies the control/eradication of cats as
a recommended management action to protect the island's biological
resources (U.S. Navy 2003).

Impacts

There is the potential for non-target impacts to the island fox due to
its similarity in size and diet to the feral cat. However, techniques
will be further developed to avoid and minimize potential impacts to the
fox. Although there may be some short-term impacts to individual foxes,
the fox population will benefit overall from the eradication of feral
cats since they are competitors for food resources and habitat. The
methodologies and potential impacts will be discussed fully in
subsequent environmental documentation for the action.

### Physical

Benefits

This action will not result in benefits to the physical environment.

Impacts

This action will not result in impacts to the physical environment.

### Human Use

Benefits

Removal of non-native species is a critical step in the restoration of
island ecosystems. The eradication of feral cats will help restore
populations of native species on San Nicolas Island. Such restoration
will provide aesthetic and recreational benefits to Navy personnel.
Because the island has restricted access, this action will not likely
provide aesthetic or recreational benefits to the general public.

Impacts

During the eradication program, there may be closures or restriction on
use of certain areas for safety reasons. Such restrictions may limit
recreational opportunities for Navy personnel. However, feral cat
control was initiated in the 1980s and Navy personnel have accommodated
this activity. Although the action is designed to be an intensive effort
over approximately 3 years, it will be compatible with the military use
of the island.

## Likelihood of Success/Feasibility

Although difficult, feral cat eradication has been successfully carried
out on at least 48 islands worldwide (Nogales et al. 2004). In northwest
Mexico, cats have been successfully eradicated from 15 islands (Wood et
al. 2002). Cats have been eradicated from large islands such as Marion
Island (290 km^2^ \[112 mi^2^\]) and Macquarie Island (120 km^2^ \[46
mi^2^\]) in the Indian Ocean (Nogales et al. 2004). San Nicolas Island
(58 km^2^ \[22 mi^2^\]) is within the size range of successful cat
eradications. The experience, expertise, and lessons learned from
previous efforts will be applied to this action to ensure its success.

The greatest challenge for this action is the presence of the island
fox. Proven techniques used in past eradications may not be available
for this action because of the potential for impact to this sensitive
species. The success of the action will be defined by complete
eradication of feral cats from the island. Therefore, should subsequent
project developments indicate that complete eradication is infeasible
due to limited available techniques or constraints, the Trustees will
not consider this action further.

Close coordination and partnering with the Navy is essential to the
success of this action. By supporting the ongoing control of cats and
identifying this action in its INRMP, the Navy has demonstrated its
support for the action. The Navy also prohibits personnel from bringing
pets to the island and will continue to do so in the future (U.S. Navy
2003). The prevention of cat reintroduction to the island in the future
is a key factor to the long-term success of the action.

## Performance Criteria and Monitoring

This action will be considered successful on the complete eradication of
feral cats from the island. The benefits of cat 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.
Monitoring of the colonies will determine breeding success,
distribution, and predation levels. Measuring statistically meaningful
population increases of these colonies may take years or even decades.
Protocols for seabird monitoring are well established and standardized.
A monitoring plan will be developed during the subsequent phase of this
action.

## Evaluation

The Trustees have evaluated this action against all screening and
evaluation criteria developed to select restoration actions and have
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 Brandt's cormorants and western gulls. Both of
these species are priorities for restoration in the SCB. This action
will also provide long-term benefits to the ecosystem on San Nicolas
Island. This action will undergo additional planning and evaluation
during future subsequent environmental documentation prepared pursuant
to NEPA and/or CEQA.

## Budget

#### Costs for years 1--3:

-   Labor \$1,121,500

-   Equipment \$184,600

-   Travel/housing \$134,200

-   Supplies \$32,900

-   Contingency...........................................\$71,900

-   Overhead \$309,000

-   **Estimated total \$1,854,100**