2007 Annual Monitoring Report (pdf 16MB) - Bolsa Chica Lowlands ...

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2007 Breeding Season for the California Least Tern, Sternula antillarum browni,at Bolsa Chica Ecological ReserveByPeter Knapp and Kelly O’ReillyCalifornia Department of Fish and Game7 November 2007California least tern chick on South Tern Island, BCER, June 2007. Photo by K. O’Reilly
Summary of 2007 Breeding SeasonAn estimated 212 pairs of California least terns, Sternula antillarum browni, (LETE)nested at the Bolsa Chica Ecological Reserve (BCER) during the 2007 breeding season.LETEs were present at BCER between 14 April and 23 August. The terns nested onSouth Tern Island (STI) (Figure 1) and Nest Site 1 (NS1) (Figure 2). The first nest wasfound 15 May on STI and the last nest was found 9 July on (NS1). A total of 392 eggswere laid in 226 nests. The average clutch size was 1.7 and the first LETE fledgling wasrecorded on 2 July. LETE fledgling success for the 2007 season was limited to 15fledglings, 3 from STI and 12 from NS1.At the beginning of the breeding season, numbers of least tern nest initiations and theabsence of disturbance or depredation were comparable to the 2006 season. In late April,it was necessary to take proactive steps to eliminate the potential threat of predation by asubadult male peregrine falcon (PEFA).At our request, J. Sipple captured the PEFA and transferred it to J. Pagel of the USFWS.The PEFA was banded (51 over D (left) and 1126-02205 (right)) and a blood sample wastaken for genetics. Pagel transported the PEFA to northern California and released it nearthe Oregon border, approximately 620 miles north of BCER.During May, LETE breeding proceeded normally with incubation and chick hatching.During the last week in June, it became apparent that chick loss was occurring, as fewLETE runners were seen chasing adults with fish. On NS1, black skimmers (BLSK)initially established nests in the area centered on grids R, S, and T (Figure 2). This areawas already the site of LETE nests. As the BLSKs expanded their nesting area,eventually covering grids O and W (Figure 2), LETE nests were lost through trampling.Also, although undocumented, it is highly probable that BLSKs aggressively defendedtheir own nests and broods by pecking at or throwing intruders into the air. This behaviorwas observed repeatedly within the BLSK colony and no LETE chicks were seen withinthese grids during surveys. Coincident with LETE chick loss in this area of NS1, fivesnowy plover (SNPL) nests protected by Mini-Exclosures (MEs) successfully hatched;however, chicks were never seen again.Simultaneous with nest and chick loss occurring in the BLSK area of NS1, LETE chickloss was discovered in the northern grids of NS1 (U – CC) (Figure 2) and on STI (Figure1). These areas had black-crowned night heron (BCNH) tracks that followed the smallertracks made by LETE chicks. Chick loss in this area was nearly 100%. Prior to thediscovery of these BCNH tracks, night surveys and monitoring had not been performed.However, subsequent to these observations, W. Ross, our contracted predatormanagement specialist, made night surveys and found BCNHs in the area described.There were no reported sightings of BCNHs or other herons or egrets on NS1 duringdaylight hours. The BCNH activity detected on STI is the suspected cause of LETE andSNPL loss there. All 11 SNPL chicks, hatched from four nests on STI, were probably lostto BCNH depredation.2
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BOLSA CHICA LOWLANDSRESTORATION PRO
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Bolsa Chica Lowlands Restoration Mo
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MutedPocket MarshSTATION 1wq1STATIO
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22Temperature35Salinity2134.5203419
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Cordgrass Planting Area (0.7 acres)
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BS PM Rep1BS PM Rep2BS PM Rep3PS1 R
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100%California Halibut Size Class D
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506647Full Tidal BasinFuture Full T
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FullMutedGrandFull Tidal Basin Tida
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FullMutedGrandFull Tidal Basin Tida
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M&A# 05-162-01August 2006 to Januar
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Page 72 and 73: Bolsa Chica Lowlands Restoration Mo
Page 112 and 113: Sampling Location CoordinatesCalifo
Page 114 and 115: Cordgrass Transplant in Bolsa Chica
Page 118 and 119: Shorebirds (cont'd)Upland birdsRudd
Page 120 and 121: 50664749484668694542417040393863717
Page 124: Ninety-five-percent of documented m
Page 128 and 129: Final ReportWestern Snowy Plover Ne
Page 130 and 131: StudyAreaMeters0 250 500 1,000Figur
Page 132 and 133: 2007 Nest LocationsNest LocationAt
Page 134 and 135: Western Snowy Plover Nesting at Bol
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2007 Annual Monitoring Report (pdf 16MB) - Bolsa Chica Lowlands ...

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