Chapters 1 - U.S. Fish and Wildlife Service

Chapter 5
established on NASA Island, but only 44 fledglings were produced. It is believed that great blue
heron predation was responsible for the high levels of mortality at this site. The implementation of
predator management on the Refuge is intended to benefit the least tern by reducing mortality in
the tern nesting colony through the control of potential predators before they enter the site.
Unfortunately, this is not always possible and predators do find access into the site. For
mammalian predators, this often occurs at night, while avian predation can occur at any time. The
predator management program as currently implemented does not result in any adverse impacts
to the nesting terns, but does provide important benefits. The overall effectiveness of the program
could be improved by enhancing visual access into the nesting area for the Eyes on the Colony
volunteers.
An issue that may arise in the near future is the predation of young least tern chicks by gull-billed
terns, a Bird of Conservation Concern. Predation of least tern chicks by gull-billed terns has been
repeatedly documented in San Diego County and at least one account of predation by a gull-billed
tern was recorded in Orange County during the 2009 nesting season. A pair of gull-billed terns
was observed picking up two least tern chicks on NASA Island in June 2009, but for unknown
reasons, the chicks were dropped and the gull-billed terns ultimately left the site. The current
predator management plan for the Refuge does not address specific measures for controlling gullbilled
terns either directly or indirectly, therefore, adverse effects to least terns as a result of gullbilled
tern predation could occur in the future. The Service is currently meeting to develop
management solutions for the benefit both species. Depending upon the types of solutions
approved to address this issue, amendments to the existing predator management plan for Seal
Beach NWR could be proposed at some time in the future. Substantive changes or additions to the
way in which predator management is implemented on the Refuge would require additional NEPA
compliance prior to the approval of the revised plan.
Pest Management
Herbicides are used on NASA Island to control invasive, weedy species. Applications within the
nesting site are conducted outside of the nesting season when the terns are not present on the
Refuge. Products that have been used in this area include Surflan AS, Glyphosate Pro 4, and
Aquamaster. Surflan AS is an effective pre-emergent that has reduced the need for extensive
annual control of weedy species. Glyphosate Pro 4 and Aquamaster are currently used for spot
treatment of weedy plants on the nesting site. USEPA has determined that oryzalin, the active
ingredient in Surflan, may be characterized as "slightly toxic" to birds in acute studies and
"practically non-toxic" in dietary studies (USEPA 1994). Glyphosate is described by the USEPA as
“no more than slightly toxic to birds” (USEPA 1993).
No mosquito monitoring or control is implemented on NASA Island or in the primary foraging
areas around the nesting island, therefore, no adverse effects to terns as a result of mosquito
control would be anticipated.
Public Use
No public use activities are permitted in the immediately vicinity of NASA Island during the
nesting season, therefore, no impacts to nesting terns are anticipated as a result of continuing the
current public use program on the Refuge. Volunteer activities including clean-up and weed
pulling on NASA Island occurs annually just prior to the commencement of nesting season. This
public use activity represents a benefit to the nesting terns.
5-56 Seal Beach National Wildlife Refuge