measuring waterbird response to salinity, depth, and foraging...

Measuring Waterbird Response to Salinity, Depth, and Foraging Area Manipulation: An Experiment to Inform

Adaptive Management

John KrauseCalifornia Department of Fish and Wildlife, Eden Landing Ecological Reserve

Susan De La CruzU.S. Geological Survey, Western Ecological Research Center, San Francisco Bay Estuary

Field Station

E12/13 Project Location

Before: Seasonal Ponds, dry in summer

2008 EIR/S Design (no reservoir, cells larger, island locations not optimized, no “mounds”)

Berms Re-aligned, Cells Smaller; New Forebay with Pump

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SNPL Nest Buffer Size: Island Location Optimized re: Disturbance

Islands Located Based on Trail Buffer max.(600 feet)

Constructed Berms with Finished Grade, Varied Slopes (5:1 to 10:1) for Enhanced Foraging/Roosting

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Excavated Channels, Built Mounds (< 12” high, 25:1 side slopes) for Topo Variation (Bird Roosting/Foraging)

5 Test Islands, to Address Cracking: Varied Surface Treatments, incl. Lime, Gravel, Oyster Shells, Lower Top Elevation

Test Islands: Gravel, Oyster Shell, Lime-treated Excavated Mud, Imported Dirt Fill

Islands Constructed

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E12-E13: Flooded, Operated 2014-16; Reached targets

Waterbird and Invertebrate Response

Research Questions

1. Was a salinity gradient established and maintained?

2. How are invertebrate community composition and abundance responding to variations in salinity level and water depth?

3. Are waterbirds responding to habitat characteristics?

E13

Methods - Habitat characteristics

• Real-time kinematics GPS elevation survey• Continuous water quality measurements in each cell with Odyssey salinity

loggers and Hach Hydrolab mini-sondes and data-sondes

Methods - Invertebrate SamplingOctober – May Benthic Invertebrates• Monthly cores (60cc, 2.6cm)*• Sampled 6 elevation zones/mound • 24 mounds

Aquatic Invertebrate Sweeps• Monthly within channels

Analyses• Generalized Linear Mixed Model with negative binomial

distribution

• Response variable: Total Benthic Invertebrate Abundance

• Fixed effects: Dissolved Oxygen, Percent Exposure, Month, Temperature, Salinity, pH, Elevation (Mound Zone); Random effects: Season Year, Pond, and Mound nested in Pond

*Sutherland et al. 2000. Marine Bio. Pomeroy & Butler. 2005. Waterbirds.

Methods - Waterbird Counts Whole Pond Counts• Monthly

• Birds assigned to 125 x 125 m grids

Foraging Mound Counts• Weekly

• Birds assigned to elevation zones

Analyses• Generalized linear mixed models with a zero-inflated

negative binomial distribution

• Response variables: Foraging and roosting small and medium shorebird abundance (mound counts)

• Fixed effects: Salinity, percent mound exposed, invertebrate density, distance to the nearest levee; Random effects: Month nested in Year, Mound nested in Pond

Average Salinity (ppt)

Targets: C1 = 20 – 50 ppt; C2 = 50 – 80 ppt; C3 = 80 - 140

Average DO (mg/L)

Benthic Invertebrate Densities

C1 C2 C3

Invertebrate Abundance Model Benthic Invertebrates

Fixed Effect Estimate Standard

Error Z Value p

Intercept 2.780 1.347 2.064 0.039

Salinity -0.008 0.008 -1.020 0.308

Temperature -0.010 0.024 -0.426 0.670pH -0.164 0.150 -1.094 0.274Dissolved Oxygen -0.065 0.024 -2.688 0.007

Mean Percent Exposure -0.004 0.001 -3.421 0.001Zone3 -0.048 0.103 -0.464 0.643Zone5 -0.086 0.104 -0.825 0.409October -0.051 0.244 -2.08 0.445November 0.286 0.202 1.42 0.157December 0.533 0.202 2.64 0.014February 0.492 0.163 3.01 0.003March 0.634 0.160 3.98 <0.001April 0.997 0.158 6.3 <0.001May 0.874 0.172 5.09 <0.001

Monthly Invertebrate Densities

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Waterbird Total AbundanceMound Scale

C1 C2 C3

Small Shorebird Distribution and Abundance on Mounds

11 Dec 201526 Dec 20159 Jan 201613 Jan 2016

Waterbird Monthly Abundance Pond Scale

Small Shorebird ModelForaging

Fixed Effect Estimate Standard error Z value pIntercept 3.796 0.797 4.766 <0.001Salinity -0.026 0.012 -2.211 0.027Benthic Invertebrate Density 0.007 0.014 1.597 0.110Distance To Levee (m) 0.005 0.006 0.917 0.359Percent Exposed (0 – 14%) 0.533 0.235 2.274 0.023Percent Exposed (15 -29 %) -0.265 0.326 -0.813 0.416Percent Exposed (30 – 44 %) 0.773 0.326 2.371 0.018Percent Exposed (45 – 59 %) -0.039 0.350 - 0.112 0.911Percent Exposed (60 – 74%) 1.011 0.259 3.900 0.173Percent Exposed (75 – 89 %) 0.280 0.617 0.454 0.154Percent Exposed 100% N/A N/A N/A NA

Small Shorebird ModelRoosting

Fixed Effect Estimate Standard error Z value pIntercept 4.859 1.008 4.822 <0.001Salinity - 0.040 0.018 1.948 0.028Benthic Invertebrate Density 0.007 0.014 0.436 0.663Distance To Levee (m) 0.001 0.003 0.483 0.029Percent Exposed (0 – 14%) 0.096 0.296 0.323 0.747Percent Exposed (15 -29 %) -0.118 0.443 -0.265 0.791PercentExposed (30 – 44 %) 0.830 0.463 1.793 0.073PercentExposed (45 – 59 %) 0.129 0.569 0.227 0.820PercentExposed (60 – 74%) 0.890 0.630 1.413 0.158Percent Exposed (75 – 89 %) N/A N/A N/A N/APercent Exposed 100% -0.626 1.022 -1.383 0.167

Medium Shorebird Model

Medium ShorebirdFixed Effect Estimate Standard error Z value p

Intercept -0.656 0.729 -0.899 0.368Salinity -0.020 0.014 -1.419 0.156Benthic Invertebrate Density 0.029 0.021 1.369 0.171Distance To Levee (m) 0.001 0.005 0.269 0.788Percent Exposed (0 – 14%) 0.021 0.257 0.081 0.935Percent Exposed (15 -29 %) 0.212 0.432 0.490 0.624Percent Exposed (30 – 44 %) 0.340 0.429 0.794 0.427Percent Exposed (45 – 59 %) -0.013 0.503 -0.027 0.979Percent Exposed (60 – 74%) -0.811 1.035 -0.783 0.434Percent Exposed (75 – 89 %) 0.788 1.099 0.717 0.473Percent Exposed 100% -19.690 29891.000 -0.001 0.999

Summary and Lessons Learned So Far….. Water Quality

• Salinities differentiate among cells, especially in drier months • Target salinities in C3 often difficult to reach • DO increases in early winter, but then drops – less circulation and macroalgae

influence?

Invertebrates• Communities highly differentiated among cells• Highest densities and diversity in C1. What about biomass?• Total abundance driven by DO and percent of mound exposed, not related to salinity

Waterbirds on mounds• Primary use was by small shorebirds• Highest abundances in C2 • Foraging small shorebirds associated with lower salinity cells and mounds that were

more inundated • Roosting small shorebirds associated with lower salinities and on mounds that were

greater distance to surrounding levees

On-going Work• Use true elevation (RTK) and staff gauge data to

calculate water depths for inclusion in models• Model response of individual dominant invertebrate

taxa to habitat variables• Evaluate invertebrate community composition

• Multi-dimensional modeling – canonical correspondence analyses, Permanova

• Model invertebrate biomass effect on shorebird abundance

• Evaluate waterbird use of pond bottom and associated habitat features

• Goals: • User-friendly model to

achieve and maintain differentiated salinity across cells; minimize pump use

• Develop niches or habitat "envelopes" for the major invertebrate species found in the South Bay Salt Pond restoration

• Collaborative effort• DU engineering and

model design• Model informed by USGS

water quality and invertebrate field data

E12/13 Hydrologic Model

Thanks to All of our Project Partners!

~ rJMlTED