2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
Zones 41 through 50 and Zone 66 (MTBs) occupy the northeastern section of Bolsa Chica. These
zones generally contain less salt panne, with broad expanses of pickleweed. Zones 49, 50, 66, and a
portion of 48 were exposed to muted tidal influence in March 2008. The other zones of the MTBs were
inundated by tidal overflow and rainwater for much of spring and summer, but were not open directly
to the FTB. The portions of these zones closest to the residential neighborhoods have an increased
amount of weedy species, particularly Zone 47.
Zones 68 through 73 are located within the FTB and are subject to full tidal influence. Zone 68
(Rabbit Island) is located on the western portion of the site between Inner Bolsa Bay and the FTB.
This zone previously had more habitat diversity than most of the other zones, with salt marsh, alkali
marsh, and upland plant species. The introduction of tidal influence in August 2006 resulted in the
inundation of much of Rabbit Island during high spring tides, causing the existing low elevation
habitats to die off as the area transitioned into mudflats and low to middle marsh habitats. Zone 69
borders Rabbit Island to the east. Zone 71 is the newly created California least tern (Sternula
antillarum browni) and western snowy plover (Charadrius alexandrinus nivosus) nesting site: Nest
Site 1. Zone 71 is a relatively unvegetated, sandy strip that gently slopes towards the FTB. The
remaining zones include the intertidal mudflat shelf on the eastern shore and open water bounded by
riprap along the shoreline.
The Muted Pocket Marsh occurs north of Rabbit Island and is not hydrologically connected to the
Bolsa Chica Lowlands; rather it experiences a muted tidal influence through a restricted tidal inlet
leading to Outer Bolsa Bay. This area is shallow intertidal and subtidal with salt marsh at the higher
elevations. The northern shore of the Muted Pocket Marsh is lined with large eucalyptus trees that
died when tidal influence was introduced. The dead trees that remain provide abundant roosting and
perching habitat for multiple bird species that use the marsh.
Survey Methodology
Zones 1 through 66 included the MTB, Future Full Tidal Basin (FFTB), and Seasonal Ponds and were
surveyed on foot by teams of field biologists. The FTB (Zones 68 through 73) was surveyed primarily
by vehicles, with multiple stops to view and record birds. Much of Zone 68 was surveyed by foot
along the pedestrian foot trail. Zone 71, which is a breeding colony for terns and shorebirds, and the
Muted Pocket Marsh were surveyed on foot.
Birding in the muted tidal basins.
Surveys began in October 2007 to mark the start of Year 2 of the
monitoring program and will continue every other month for a 2-year
period (see Appendix 1-A for survey dates). Surveys were conducted in
2008 over a two-day period at each survey interval in such a way as to
minimize the possibility of double-counts between the two days. The FTB
and Seasonal Ponds were normally surveyed the first day, and the Muted
Pocket Marsh, FFTB, and MTBs surveyed the second day. The surveys
were conducted during a tide low enough to expose the mudflat on the
eastern shore of the FTB, referred to often as the cordgrass bench, generally
within a predicted oceanic tide range of +0.9 to +0.3m (+3 to +1 ft) NAVD.
At this tide, the large sand shoals that had formed in the inlet of the FTB
where large numbers of gulls, cormorants, and pelicans loaf in the
afternoon were only minimally exposed.
Merkel & Associates, Inc. 74