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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
individual birds observed was fairly consistent over the year with the exception of June, when the
count was reduced by more than one half due to the absence of large groups of shorebirds.
Throughout most of the year western sandpiper (Calidris mauri) was the most common species, with
shorebirds the most abundant guild overall. This changed in June when most of the shorebirds left
Bolsa Chica for their breeding grounds and were replaced by species that nest in the area. These
species were mostly the aerial fish foragers (primarily terns), but also included some of the larger
shorebirds such as black-necked stilt (Himantopus himantopus), and American avocet (Recurvirostra
americana). The second most abundant guild was dabbling ducks/geese, which had high counts in
February, April, and December but remained present year round in smaller numbers.
Mudflats and inundated salt panne were the most utilized habitat type, although species richness was
highest in the salt marsh. In 2008 the FTB was utilized by 49.7% of all birds observed, representing
103 species. Nest Site 1 (NS1) in the FTB was highly utilized by aerial fish foragers, particularly
during the April through August surveys when the terns and skimmers were nesting. The Future Full
Tidal Basin (FFTB), Seasonal Ponds, and MTBs were very important habitat for dabbling ducks,
shorebirds, and upland birds. The most abundant upland bird was Belding’s Savannah sparrow, which
utilized the pickleweed-dominated salt marsh. The Muted Pocket Marsh is highly utilized by
shorebirds and dabbling ducks and had even more birds per hectare than the FTB.
Surveys for the state endangered Belding's Savannah sparrow were performed in April and May 2008.
Two complete surveys were done in 2008 in order to improve the reliability of the number of
territories recorded. A total of 177 territories were identified within the study site in April 2008 and
208 territories in May 2008. These numbers are lower than those recorded in 2007, but comparable to
the counts in 2006. Territories appeared to be relatively evenly dispersed throughout areas where
pickleweed-dominated salt marsh occurred. Using the area of salt marsh available and the maximum
number of territories recorded, the average territory size was estimated to be 1,836 m 2 , much larger
than the average territory size noted in the available literature (304 m 2 to 626 m 2 ). While the available
habitat would suggest low-density occupancy by Belding’s Savannah sparrow, the highly fragmented
nature of the present salt marsh results in considerable area that is unsuitable for breeding use. As the
system matures, it is expected that more of this area will become suitable and will be occupied by the
sparrows. The FFTB supported the most territories, followed by the MTBs, then Seasonal Ponds.
California least tern (Sternula antillarum browni) nest monitoring occurred on North Tern Island
(NTI), South Tern Island (STI), NS1, Nest Site 2 (NS2), and Nest Site 3 (NS3). The terns nested
primarily on STI and NS1, although one unsuccessful nest was located in the Seasonal Ponds in Zone
11. The least terns did not utilize NTI, NS2, or NS3. From an estimated number of 217 pairs, a total
of 432 eggs were laid in 242 nests. These numbers are a slight increase from those of 2007. The
average clutch size was 1.8 eggs per nest and the first least tern fledgling was recorded on 23 June.
California least tern nest predation was low at 19 (7.9% of all nests) nests. Seven (2.9%) nests were
abandoned prior to hatching, and one nest was lost to flooding. Fledgling success for the 2008 season
ranged from 100-150 fledglings, for a rate of 0.41 to 0.62 fledglings per nest. This is compared to 15
fledglings in 2007 and a rate of 0.07 fledglings per nest.
The western snowy plover (Charadrius alexandrinus nivosus) nested on STI, NS1, NS3, and a number
of cells within the Seasonal Ponds, with a total of 67 nests. From the 193 total eggs laid, 174 chicks
were produced. Two of the 67 nest attempts were lost to predators; however, three nests were
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