DOI: 10.5061/dryad.j3tx95xv2
title: Elkhorn Slough National Estuarine Research Reserve: Monitoring waterbirds

description: The purpose of this monitoring is to track migratory and resident
 shorebirds, waders, and waterfowl using the tidal wetlands of Elkhorn
 Slough in central California, USA. While this modest program will
 not be sufficient to detect subtle alterations, we will be able to detect
 dramatic changes. By comparing our results to those from other wetlands
 along the coast, we can determine whether the changes are due to local
 factors affecting only the Slough (loss of foraging areas due to tidal
 scour, elimination of prey due to oil spill, etc.) or regional processes
 affecting the whole coast (breeding failure, El Niño effects on prey
 recruitment, etc.). Elkhorn Slough National Estuarine Research
 Reserve teams have been counting waterbirds since 2003 to the present
 (2025 at current data submission).
description: Using spotting scopes and binoculars, surveys are conducted
 during peak migration, once or twice in the fall (September and November)
 and once or twice in the spring (early-mid March, mid-late April). Surveys
 take place during spring tides, within 2 hours of low tide listed between
 +2.0 and -1.5 ft. We submit our November survey data to Point Blue as part
 of their annual Pacific Flyway Shorebird Survey (PFSS). 
 Four sites are surveyed on the same day (or within a few days of
 each other), coinciding with the low tide: Main Channel (by boat), North
 Harbor/Bennett Slough West, Parsons Slough, and Oak Marsh/Shark Flats; one
 site (Pelican Marsh/Estrada) is surveyed on the same day at high
 tide. Main Channel: from the Hwy 1 bridge to Hudson
 Landing. Divided into 4 sections (Section A-E), each of which is surveyed
 separately; see additional information below. We used
 cell phones to communicate between the two boats to avoid double counting
 (particularly grebes and terns in center of channel) – one boat surveys
 waterbirds on the north bank and the other boat surveys the south bank.
 Bring Kvitek bathymetry GIS for difficult navigation from Kirby to Hudson.
 Start the survey at the Hwy 1 bridge and work up towards Hudson.
 Section A – Bridge to Dairy Section B – Dairy
 to mouth of Parsons Slough Section C – Parsons Slough
 mouth to Coyote Island Section D – Coyote Island to
 Kirby Park Dock Section E – Kirby Park Dock to Hudson
 Landing Bridge North Harbor/Bennett Slough West: on
 mudflats off Jetty Road, Moss Landing State Beach. Survey the mud/sand
 flats on the northern half of North Harbor (from the seal haul out, all
 the way to Jetty Rd), from various vantage points, as well the southern
 portion of Bennett Slough West. Parsons Slough: at
 ESNERR, near end of Parsons Overlook trail. Walk down peninsula at end of
 trail and gradually walk about 20 m to either side of point; survey
 mudflats visible from this area. Oak Marsh/Shark Flats:
 at ESNERR, on either side of berm just past footbridge on Oak Marsh loop
 trail. Survey Oak Marsh, and Shark Flats on other side. (Note: this site
 surveyed from 2003 – 2018 only). Pelican Marsh/Estrada:
 at ESNERR, from water monitoring station at tide gates, on road running
 down from Pelican Marsh Overlook. Survey areas visible from this vantage
 point. Then drive to Estrada Overlook and survey Estrada Marsh.
description: # Elkhorn Slough National Estuarine Research Reserve: Monitoring
 waterbirds Dataset DOI:
 [10.5061/dryad.j3tx95xv2](https://doi.org/10.5061/dryad.j3tx95xv2) ###
 Files and variables: **File: Data_Curation_Areas_Oct2024.kmz**
 **Description:** This is a Google Earth file showing how the Elkhorn
 Slough National Estuarine Research Reserve subdivides the estuary into
 regions and areas that are included as columns in the dataset #### File:
 Waterbirds_survey_sites.kmz **Description:** Google Earth file of the
 waterbird survey site areas #### File: Elkhorn_Slough_Waterbirds.csv
 **Description:** Waterbird count data ##### Variables * Date: Survey date
 * Year: Survey year * Month: Survey month * Day: Survey day * Month_1:
 Survey month * Season: Meteorological season * Oceanographic_season:
 Upwelling (March-August), Oceanic (September-October), Davidson
 (November-February) * Subregion: finer categorization of region used by
 ESNERR; for waterbirds surveys specifically, the boundary between Main
 Channel - Section C and D - separates Lower from Upper Slough,
 respectively; see KMZ file provided separately * Area: Parsons Slough
 complex (Parsons Slough, Oak Marsh/Shark Flats), Pelican Marsh complex
 (Pelican Marsh, Estrada), Main Channel (Sections A-E) * Start_time: Survey
 start time * End_time: Survey end time * Common_Loon: * Pacific_Loon: *
 Red-throated_Loon: * Pacific/red-throated_Loon: Additional counts of
 PALO/RTLO not identified to species * Pied_billed_Grebe: * Horned_Grebe: *
 Eared_Grebe: * Horned/Eared_Grebe: Additional counts of HOGR/EAGR not
 identified to species * Western_Grebe: * Clark's_Grebe: *
 Western/Clark's_Grebe: Additional counts of WEGR/CLGE not identified
 to species * White_Pelican: * Brown_Pelican: * Double-crested_cormorant: *
 Brandt's_cormorant: * Pelagic_cormorant: * Cormorant_sp: Additional
 counts of cormorants not identified to species * Great_Blue_Heron: *
 Green_Heron: * Black-crowned_Night_Heron: * Great_Egret: * Snowy_Egret: *
 Canada_Goose: * Brant: * Duck_sp: Additional counts of ducks not
 identified to species * Mallard: * Northern_Pintail: * Green-winged_Teal:
 * Blue-winged_Teal: * Cinnamon_Teal: * Northern_Shoveler: * Gadwall: *
 American_Wigeon: * Canvasback: * Ring-necked_Duck: * Greater_Scaup: *
 Lesser_Scaup: * Scaup \_sp: Additional counts of Scaup not identified to
 species * Surf_Scoter: * White-winged_Scoter: * Scoter_sp: Additional
 counts of Scoter not identified to species * Common_Goldeneye: *
 Bufflehead: * Red-breasted_Merganser: * Ruddy_Duck: * American_Coot: *
 Black-bellied_Plover: * Snowy_Plover: * Semipalmated_Plover: * Killdeer: *
 Black-necked_Stilt: * American_Avocet: * Greater_Yellowlegs: *
 Lesser_Yellowlegs: * Yellowlegs_sp: Additional counts of yellowlegs not
 identified to species * Willet: * Spotted_Sandpiper: * Western_Sandpiper:
 * Least_Sandpiper: * (Western/Least_sandpiper): Additional counts of
 WESA/LESA not identified to species * Whimbrel: * Long-billed_Curlew: *
 Marbled_Godwit: * Ruddy_Turnstone: * Sanderling: * Dunlin: *
 Short-billed_Dowitcher: * Long-billed_Dowitcher: * Dowitcher_sp:
 Additional counts of dowitcher not identified to species *
 Shorebirds_small_unidentified: Additional counts of small shorebirds not
 identified to species * Shorebirds_large_unidentified: Additional counts
 of large shorebirds not identified to species * Wilson's_Phalarope: *
 Red-necked_Phalarope: * Bonaparte's_Gull: * Heerman's_Gull: *
 Mew_Gull: * Ring-billed_Gull: * California_Gull: *
 California/ring-billed_Gull: Additional counts of CAGU/RBGU not identified
 to species * Herring_Gull: * Thayer's_Gull: * Western_Gull: *
 Herring/Western_Gull: Additional counts of HEGU/WEGU not identified to
 species * Glaucous-winged_Gull: * Gull_sp: Additional counts of gulls not
 identified to species * Forster's_Tern: * Elegant_Tern: *
 Caspian_Tern: n/a represents missing data - sites/dates where no surveys
 were conducted