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

Ninety-five-percent of documented mortality was due to depredation (175 chicks and 65eggs preyed upon). As described above, most mortality was attributed to BCNHs (168chicks) and BLSKs (65 nests, 97 eggs). In addition, six chicks were lost to a Great BlueHeron and ants depredated one chick. Other potential predators on LETE included gulls,Caspian terns, white-tailed kites, red-tailed hawks, American kestrels, American crows,common ravens, coyotes, and California ground squirrels.Drought conditions and BLSK activity destroyed most of the vegetation on NS1; thuslimiting chick cover for both LETEs and SNPLs.P. Knapp (CDFG) served as the primary LETE monitor and was assisted by B. Peterson(Merkel & Assoc.), L. Hays (CDFG volunteer), and Kelly O’Reilly (CDFG).Management Recommendations for California Least Terns at Bolsa ChicaRegular night surveys are necessary to assess BCNH activity and other potentialnocturnal avian and mammal activity on both NS1 and STI. Predator management will berequired during evening hours as well as during daylight hours.Preventative measures such as raptor capture and relocation should be considered whenwarranted. During early spring 2007, as many as three PEFAs were seen loafing andpreying upon birds at BCER in the vicinity of NS1 and STI. The male PEFA mentionedabove (51 over D) returned to BCER in October and is regularly seen at NS1 along withan adult female PEFA. We hope these raptors will move out of the area after winter.A method of protecting LETE nests from BLSK nesting behavior must be developed.LETEs are early nesters; whereas, BLSKs nest later in the season after LETE nests andhatching have commenced. The use of an open top ME is a possibility; but the success ofthis approach would depend upon the adult LETE’s acceptance of the ME. The placementof chick fencing may limit the expansion of BLSKs into LETE nesting areas; however,this method may have an adverse affect on BLSK productivity due to the potential loss ofBLSK chicks within a confined area.Finally, cover, in the form of vegetation, is necessary on NS1. Vegetative growth mayoccur during the winter of 2007-2008, provided there is sufficient rainfall. Given thepossiblility of continued drought conditions in Southern California, we recommendseeding with native sand dune species, such as beach primrose (CamissoniaCheiranthifolia) and a watering regime to encourage plant germination on NS1.Figure 1. South Tern Island and Figure 2. Nest Site 1, follow on pages 4 and 5.3