Chapters 1 - U.S. Fish and Wildlife Service

Chapter 4
condition that could be influencing the current trend is the level of the tides relative to the height
of the existing vegetation. Tides of 6.5 feet (MLLW) or higher, which occur regularly in the late
summer usually in darkness and the fall or winter in the early morning, force the rails to find
higher ground on debris or the edge of the marsh where there is little cover (Zembal et al. 2006).
This exposes the rails to potential avian and mammalian predators.
Current management activities conducted on the Refuge to protect and assist in the recovery of
the light-footed clapper rail include pre-season nesting preparation, monitoring during the nesting
season, minimizing human disturbance, and implementing predator management. Pre-season
nesting preparation involves surveying the current condition of the nesting platforms that have
been installed in Anaheim Bay to provide cover and high tide refugia for clapper rail adults, chicks,
and eggs. Currently there are approximately 85 of these nesting platforms installed throughout
the salt marsh. They are essential to the long term survival of the Refuge’s rail population because
the probability of a natural nest surviving even moderately high tides in Anaheim Bay’s primary
salt marsh habitat is extremely low. This is due to the elevation of these high tides relative to the
height of the cordgrass. The majority of the marsh is almost completely inundated during
moderately high or higher tides. Only one area in the marsh seems to be high enough to avoid
complete inundation during these tides. This area is located generally between Hog Island and
Perimeter Pond, where active natural clapper rail nests are documented annually. Prior to the
nesting season, all nesting platforms in need of repair are removed, refurbished, and replaced or
they are discarded and replaced with a new platform. Platforms that based on monitoring do not
appear to be used by clapper rails may be removed and relocated, or discarded if they are in
disrepair.
Use of nesting platforms on the Refuge began in 1987, when 28 floating rafts were installed in the
marsh. Each raft consisted of a wooden platform anchored with two wooden dowels. The dowels
were installed in such a way that the platform was anchored but could also float up and down with
the tide. To provide cover, dense tumbleweed was secured on top of the platform. Rails began
using the platforms for nesting the first year they were installed. Over the past twenty years, the
design of the platforms has changed to include a more secure cover over the nesting platform.
Other improvements were made to: 1) provide increased stability during strong winds and high
tides; 2) eliminate the potential for avian predator perching; 3) increase durability; 4) reduce
construction costs; and 5) increase the easy of initial construction and subsequent repairs. Nesting
platforms have been installed throughout the marsh, with the greatest number of platforms located
between Oil Island and NASA Island and between NASA Island and Hog Island.
Other activities that have been implemented on the Refuge to improve nesting habitat for the rail
occurred in 1982 and 1985. In 1982, five nesting hummocks were constructed in the marsh at an
elevation above extreme high tide. Over time, natural erosion processes have reduced the height
of the hummocks to lower than optimal elevation and they are no longer used for nesting. In 1985,
eleven nesting mounds were created in three separate locations by cutting existing berms and old
roadways that extended from upland habitat into the marsh. Rail nesting occurred on these
mounds for several years, until eggs predation became too common and the rails stopped using the
sites for nesting.
Clapper rail monitoring on the Refuge is conducted in partnership with NWSSB and involves
monthly monitoring of clapper rail nests, spring clapper rail call counts, and fall high tide call
counts. Call count surveys are conducted during the breeding season and throughout the marsh to
estimate the ratio of males to females and of paired to unpaired rails. High tide counts are
conducted at least once annually in the fall during daytime +6.7 foot or higher tides. During these
very high tides, rails are forced to seek higher ground, generally in pickleweed habitat or on
4-66 Seal Beach National Wildlife Refuge