Chapters 1 - U.S. Fish and Wildlife Service

Chapter 3
For the California least tern, annual pre-nesting site preparation involves killing weedy
vegetation at the NASA Island nesting site through the use of chemical or mechanical means;
cleaning up any debris and/or trash; improving substrate quality when necessary by spreading
additional clean, light sand and shell fragments over some or all of the site; inspecting and
repairing the electrified perimeter fence; and addressing any erosion problems around the
outer edges of the nesting site. In 2007, approximately 40 percent of NASA Island was
mechanically scraped and clean, light sand was deposited over the prepared area. Volunteers
then assisted in manually removing vegetation from the remainder of the site. This was
followed in 2008 by the placement of crushed oyster shells on those areas of the site that were
recently covered in clean sand. Vegetation growing on the site is normally killed in late winter
through use of approved herbicides or salt water treatments.
California least tern monitoring begins at NASA Island when the first least terns are observed
on the Refuge, which is generally between April and early May of each year. Monitoring is
conducted one day per week until the terns leave the nest site, which usually occurs in late July
or August each year. To monitor the nesting terns, terra cotta tiles are placed inside the
colony for grid marking. These tiles also provide protection for tern chicks from avian
predators. The grid spacing is generally set at 30 feet. This grid assists the tern monitors in
recording and mapping tern nests. Monitoring data provide information about the number of
adults present at the nesting site, the numbers of nests, chicks, and successful fledges, and
information about adult, chick, and/or egg mortality and/or predation. This monitoring data
are provided to the California Department of Fish and Game for inclusion in the statewide
California Least Tern Annual Report and are also maintained at the Refuge Headquarters for
use in comparing population levels and productivity from year to year and over extended
periods of time.
To reduce the potential for predation by avian predators, particularly crows, ravens, and gulls,
a least tern predator monitoring program is implemented annually on the Refuge during the
nesting season. This program, often referred to as the Eyes on the Colony Program, involves
the use of volunteers and/or contractors who are stationed at a lookout site a short distance
from the nesting colony. From this location, they can observe the activities going on at the
nesting site. When participants observe potential avian predators in the vicinity of the nesting
colony, they take actions to haze (scare off) the potential predators from entering the site.
Participants stay in contact with the Refuge Manager to provide updates on site conditions and
nesting activity, as well as to report potential threats or apparent evidence of predation
activity.
Pre-nesting season preparation for the light-footed clapper rail involves conducting annual
inspections of, and when necessary, repairs to the clapper rail nesting platforms that have been
placed within the marsh (refer to Chapter 4 for additional information). Navy contractors and
Refuge volunteers assist the Refuge Manager in this task. The design of these platforms is
continually being improved to ensure that the rails have safe and secure locations to nest and
take refuge during higher high tide events that occur throughout the year. Each year a
number of new platforms are placed within the marsh to replace old or damaged platforms.
From 2003 to 2008, the total number of nesting platforms located within the Refuge was
between 79 and 82 (Hoffman 2009).
Light-footed clapper rail monitoring involves annual fall high tide counts and spring call
counts. Fall high tide counts are conducted at least once a year in the fall during daytime +6.7
foot or higher tides in order to estimate the overall Refuge population. Spring call counts are
conducted annually during early phases of rail breeding, usually in March or April in order to
3-14 Seal Beach National Wildlife Refuge