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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
and April surveys. Northern shoveler was present in small numbers only during the surveys in June
and August. Several brant (Branta bernicla) were recorded foraging in eelgrass in the FTB.
The third most abundant guild in 2008 was upland birds, primarily due to the inclusion of Savannah
sparrow (Passerculus sandwichensis) in this guild, including both the Belding’s Savannah sparrow, a
species that remains in the salt marsh year round, and any other migrating Savannah sparrows. The
number of individuals in the guild remained fairly stable for the entire year although there was a small
drop in numbers during April (711 individuals) and August (671 individuals). June had the highest
count of upland birds with 1,244 individuals and made up 32.6% of all birds observed during that
survey. Counts during the winter months were comparable to the June count including; 1,162
individuals (13% of all birds) in October, 1,012 individuals (9% of all birds) in December, and 1,106
individuals in February. The highest numbers for Savannah sparrow were during the month of October
when a total of 639 individuals were counted. February and August, which correspond with the
beginning and end of the Belding’s Savannah sparrow breeding season, were the lowest numbers with
156 individuals observed. June counts were much higher at 416 individuals.
Other abundant upland species include house finch (Carpodacus mexicanus), and mourning dove
(Zenaida macroura). Cliff swallow (Petrochelidon pyrrhonota), northern rough-winged swallow
(Stelgidopteryx serripennis), barn swallow (Hirundo rustica), violet-green swallow Tachycineta
thalassina, and tree swallow (Tachycineta bicolor) were all observed at Bolsa Chica although the
highest counts of each species were observed at different times of the year. Northern-rough winged
swallow (83 individuals) and violet-green swallow (42 individuals) were most numerous in February.
Tree swallow was most numerous in both February and December with 23 individuals observed each
month. Cliff swallow were most numerous in June (222 individuals) and barn swallow most numerous
in August (107 individuals). The great-tailed grackle (Quiscalus mexicanus), not native to the area but
an invading species from Sonora or southern Arizona, was observed breeding during April and June
surveys but was not observed during any other surveys.
Aerial fish foragers were the fourth most abundant guild and accounted for 8.8% of all birds observed
over the year. The elegant tern was the most common, accounting for 62.1% of all aerial fish foragers.
The majority of the remaining species in this category included; in descending order of abundance,
black skimmer, Forster’s tern (Sterna forsteri), Caspian tern, California least tern, and royal tern. All
of these species nest at Bolsa Chica in the area of the FTB and had their highest numbers during the
June survey. These species were most likely undercounted during June and August due to limited
access to their high-density nesting area in Zone 71 (Nest Site 1). It is important to note that the
elegant tern count (maximum of 1,330 in April 2008) only reflects their usage of Zone 71, which
represents only a small portion of the total breeding population at the Bolsa Chica Ecological Reserve.
The majority of elegant terns nested at North Tern Island in Inner Bolsa Bay, outside the survey focus
of this monitoring program (see Figure 0-1). An estimated 7,000 elegant tern nested on NTI in 2008
(Mike Horn, pers. comm.).
Other aerial fish foragers included belted kingfisher (Megaceryl alcyon), which were seen in low
numbers, and brown pelican (Pelecanus occidentalis), which were observed loafing and foraging
nearly year-round (none detected in February) in moderate numbers.
Diving ducks/grebes/cormorants were the fifth most abundant guild and accounted for 4.9% of all
birds observed over the year. Ruddy duck was the most common diving duck accounting for 46.6% of
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