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

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Bolsa Chica Lowlands Restoration Monitoring2007 Annual ReportCalifornia Least Tern and Western Snowy Plover MonitoringMethodologyCalifornia least tern (Sternula antillarum browni) nest monitoring occurred on North Tern Island(NTI), South Tern Island (STI), Nest Site 1 (NS1), Nest Site 2 (NS2), and Nest Site 3 (NS3). NTI andSTI are located in Inner Bolsa Bay, outside of the project survey area, but are included in this report inorder to give a more complete understanding of tern reproductive success at the Bolsa Chica complex.NS1, NS2, and NS3 are newly created nesting islands within the project area; NS1 is in the FTBbetween the FTB and Inner Bolsa Bay, NS2 is located within Zone 42 of the southern MTB, and NS3is located in Zone 14 of the FFTB. Western snowy plover (Charadrius alexandrinus nivosus) nestsites included all tern colonies listed above but also included the Seasonal Ponds (Zones 1 through 37).The principal survey effort for least terns and western snowy plover was undertaken by CaliforniaDepartment of Fish & Game seasonal staff member, Peter Knapp. Merkel & Associates biologist,Bonnie Peterson, participated intermittently in the survey efforts as support and to aid in collectingdata for report preparation. STI and NS1 were surveyed by vehicle from the West Levee Road prior toarrival of the least terns and then on foot. NTI was used primarily by nesting elegant terns (Thalasseuselegans) and black skimmers (Rynchops niger) and therefore required minimal monitoring for ternsand plovers. NS2 was surveyed by vehicle from the East Levee Road weekly using a spotting scopeand once a month on foot. NS3 was surveyed by vehicle from the north end of the site. The largemajority of suitable western snowy plover nesting habitat in the Seasonal Ponds was visible from theroad network. The observer(s) would slowly drive along the roads that subdivide this area. Frequentstops were made to examine specific areas adjacent to the road with binoculars or spotting scopewithout exiting the vehicle.NS1, NS2, and NS3 are sectioned by markers, which form the basis for data recording. NS1 issectioned south to north from A though CC in a regular grid. Each least tern and snowy plover nestlocated on NS1 was marked with a numbered tongue depressor and mapped for ease of relocation onsubsequent visits.California least tern monitoring began as soon as the terns started arriving at Bolsa Chica in mid-Apriland continued until the terns had fledged and left the breeding grounds in late August. The observerswould walk active tern colonies and mark and record the section of all new nests. This activitytypically occurred between 0800 and 1200 hours, 1 to 2 times per week. Observers would record anyhatched, abandoned or depredated nests. Any signs of disturbance within the tern colonies were alsorecorded. At other times during the week, observations on the status of the colony were made fromobservation points outside of the colony. Observations on least tern chicks and fledglings were madeevery 1 to 2 days to determine hatching and fledging success.Beginning late-March, surveys for nesting western snowy plovers were conducted at least twice aweek, sometimes 4 or 5 times a week, until the beginning of September. Data collected during thisstudy included the gender of the incubating adult, length of incubation (days), number of eggs in theclutch, condition of the nest (e.g. signs of disturbance), and the fate of each nest (hatched, predated, orabandoned). Observations of western snowy plover distribution were also recorded by cell number,throughout the study area, not just those birds associated with nests. Close examination of nests wasusually conducted only once or twice per nest. As snowy plover nests were located they wereprotected by Mini-Exclosures (MEs) placed over the nest.Merkel & Associates, Inc. 53
Bolsa Chica Lowlands Restoration Monitoring2007 Annual ReportObservations of snowy plover broods were made 3 to 5 days per week. It was usually possible tofollow the movements and determine the fate of the chicks from each brood since there was dispersionover space and time sufficient to differentiate between broods. These regular brood observations wereconducted to determine chick survival or fledgling production, as well as to detect movement betweencells and use of specific cells for brood rearing.ResultsCalifornia Least TernThe complete 2007 results for the California least tern breeding season at Bolsa Chica EcologicalReserve can be read in the annual report (Knapp and O’Reilly 2007)(Appendix 1-F).California least terns arrived at Bolsa Chica on April 14, 2007 and were last observed on the site on August23. The terns nested on STI and NS1 and did not utilize NTI, NS2, or NS3. The overall data were notbroken down by individual site. The first nest was found 15 May on STI and the last nest was found 9 Julyon NS1. From an estimated number of 212 pairs, a total of 392 eggs were laid in 226 nests. The averageclutch size was 1.7 and the first least tern fledgling was recorded on 2 July. California least tern nestpredation was high at 65 (31%) nests and fledgling success for the 2007 season was limited to 15 fledglings(3.8%), 3 from STI and 12 from NS1.Ninety-five-percent of documented least tern mortality was due to depredation (175 chicks and 65 eggs).Most mortality was attributed to the black-crowned night heron (Nycticorax nycticorax; 168 chicks) andblack skimmers (65 nests, 97 eggs). Black-crowned night heron tracks were found on NS1 (U – CC) andon STI. At the same time, chick loss in these areas was nearly 100%. On NS1, black skimmers initiallyestablished nests in the area centered on grids R, S, and T, then expanded into grids O and W. This areawas already the site of least tern nests that were subsequently lost through trampling and potentiallyaggressive behavior by skimmers defending their nests and broods. In addition, 6 chicks were lost to agreat blue heron (Ardea herodias) and ants depredated one chick. Other potential predators included gull,Caspian tern (Hydroprogne caspia), white-tailed kite (Elanus leucurus), red-tailed hawk (Buteojamaicensis), American kestrel (Falco sparverius), American crow, common raven, coyote (Canis latransclepticus), and California ground squirrel (Spermophilus beecheyi nudipes). A subadult male peregrinefalcon (Falco peregrinus) was also captured and relocated from Bolsa Chica to eliminate the potentialthreat of predation.Drought conditions and black skimmer activity destroyed most of the vegetation on NS1, limiting chickcover, which also contributed to the low fledging success.Merkel & Associates, Inc. 54
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BOLSA CHICA LOWLANDSRESTORATION PRO
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Page 20 and 21: MutedPocket MarshSTATION 1wq1STATIO
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Sampling Location CoordinatesCalifo
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Cordgrass Transplant in Bolsa Chica
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Shorebirds (cont'd)Upland birdsRudd
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2007 Breeding Season for the Califo
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Final ReportWestern Snowy Plover Ne
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StudyAreaMeters0 250 500 1,000Figur
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2007 Nest LocationsNest LocationAt
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Western Snowy Plover Nesting at Bol
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