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

Bolsa Chica Lowlands Restoration Monitoring
2008 Annual Report
about half as many territories as in 2007. Zone 36 at the eastern end of the site is normally wet all
year; but in 2008, this zone dried out and was apparently not as suitable for the sparrow. It supported
19 territories in 2007 and only 2 in 2008. All other zones in the FFTB decreased by small numbers
between 2007 and 2008.
The counts in the MTB were the most variable, ranging from counts of 45 territories in April to 72
territories in May, while having had a count of 117 territories in 2007. The west MTB (Figure 0-1)
was opened to tidal influence from the FTB on March 5, 2008, which inundated much of the
pickleweed growing at low elevations (in Zones 50, 66, and 49). In conjunction with rainfall, tidal
waters flowing from the west to the central basin resulted in inundation of some low pickleweed in the
central MTB as well (Zones 48 and some of 46). Belding’s Savannah sparrow were regularly
observed defending territories that were inundated.
Zones 41, 45, and 46 decreased from the 2007 counts by a minimum of 17 (63%), 14 (56%), and 9
(45%) territories respectively. These zones are normally dry and covered in pickleweed and remained
unchanged between the 2007 and 2008 breeding season.
Using the area of undisturbed salt marsh available and the maximum number of territories recorded per
cell over both surveys within Zones 2-29, the average territory size was estimated to be 1,836m 2 ,
ranging from 693 m 2 in Cell 26 to 3,714m 2 in Cell 9. This is a very course calculation and does not
take into account the observed patchy distribution of the birds in the marsh or the considerable areas of
what appeared to be suitable habitat that remained unoccupied.
Table 1-21. Belding’s Savannah sparrow territories at Bolsa Chica in 2007 and 2008
Zone
# of Territories # of Territories # of Territories Salt Marsh
April 2007 April 2008 May 2008 Available (ha)
Full Tidal Basin n/a 5 10 5.0
Future Full Tidal Basin 143 72 76 25.3
Muted Tidal Basins 118 45 72 44.5
Seasonal Ponds 90 53 47 11.6
Pocket Marsh n/a 2 3 4.6
Total 351 177 208 91.0
n/a = not counted during 2007
Discussion
The count of Belding’s Savannah sparrow territories in 2008 was considerably lower than in 2007, but
comparable to the counts (201 territories) in the 2006 annual survey conducted by CDFG (Zembal et
al., 2006) within a similar area of Bolsa Chica. The 2007 increase may have resulted from a
movement of birds out of the newly created FTB. Prior to inundation the area of the new FTB
supported pickleweed-dominated salt marsh where Belding’s Savannah sparrow regularly nested and
foraged. When the FTB was excavated and later opened to the ocean in August 2006, much of the
pickleweed in that area was lost, which may have forced the sparrows to move the following year
(2007) to more suitable habitat in the salt marsh and salt panne areas of the FFTB, MTBs, and in
particular the Seasonal Ponds.
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