Proceedings of the Third International Conference on Invasive ...

Chapter 4: Spartina Control and Management<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaShorebirds/m 2 /hr86420Native Tilled Sprayedmudflat meadow /mowedmeadowSprayedmeadowUntreatedSpartinameadowFig. 1. A summary <strong>of</strong> <strong>the</strong> comparative use <strong>of</strong> Spartina affected tideflats byshorebirds during <strong>the</strong> winter/spring migration in 2003 based on foragingflux density data from remote sensing cameras as a funciton <strong>of</strong> Spartinacontrol method. Bars = Std. Err.Bird number / ha / 15 minutes1500 Western SandPiperDunlin1000Untreated Spartina50001500100050001500100050001500Sprayed SpartinaTilled Spartinatilled Spartina meadow, sprayed Spartina meadow, spraymowedSpartina meadow and an untreated Spartinameadow. Data collected included beak probe density,footprint density, fecal dropping density, visual countsduring peak migration in spring 2003 and winter <strong>of</strong>2003/2004, and remote monitoring with video cameras inwinter/spring 2003. The study site was on Willapa NationalWildlife Refuge property at <strong>the</strong> south end <strong>of</strong> Willapa Bay.The Spartina infestation was 10 to 14 years old and coveredover 1000 hectares (ha). Treatment sites were adjacent toeach o<strong>the</strong>r and large enough to be considered ecologicallysignificant units (>60 ha). This part <strong>of</strong> <strong>the</strong> bay supported anabundant bird population prior to infestation by Spartina(Jacques 2002). Although <strong>the</strong> sites had similar bathymetryprior to Spartina infestation, <strong>the</strong>ir current elevations weremeasured to be greater than 35 centimeters (cm) above <strong>the</strong>adjacent mudflats. The bare mudflat site is and has beenSpartina-free. The tilled site has been treated since2000/2001 with mowing, tilling, and spraying for cleanup. Ithas been relatively free <strong>of</strong> Spartina since 2002. The sprayedand spray-mowed sites were treated with 2 gallons/acre <strong>of</strong>glyphosate (Rodeo®) in summer <strong>of</strong> 2002 and had follow-upspraying in summer <strong>of</strong> 2003. The spray-mowed site wasmowed to a level <strong>of</strong> approximately 14 cm during <strong>the</strong> spring<strong>of</strong> 2003 to remove dead stubble and encourage bird usage.The untreated Spartina area is a large meadow comprisingmore than 200 ha at <strong>the</strong> southwest end <strong>of</strong> <strong>the</strong> bay.Shorebird dataBeak probe density, footprint density, and fecaldropping density (#/0.25 m 2 ) data were collected on May 13,2003, using five replications per habitat per location, withfive subsample counts per replication. For each replication,comparative habitats (treatments) were located within 20feet <strong>of</strong> each o<strong>the</strong>r. Remote monitoring <strong>of</strong> sites was doneusing video cameras in winter/spring 2003. A Mitsubishi1000500Bare mudflat011/22/03 12/12/03 1/1/04 1/20/04 2/9/04Date <strong>of</strong> observationFig. 2. Visual counts <strong>of</strong> <strong>the</strong> major shorebird species in Willapa Bay inWinter 03/04 as a funciton <strong>of</strong> <strong>the</strong> Spartina control method.Time Lapse Security Recorder, Model #HS-1280U, wasused to record <strong>the</strong> black and white image from a SuperCircuits PC23C camera with a 12-mm 1/3” CS TV lens.Power was provided using three 12-volt deep cycle marinebatteries and a 16-watt solar pane with a DC to AC, 12-volt,150-watt inverter. Cameras were mounted in wea<strong>the</strong>rpro<strong>of</strong>camera housing on 7-m poles 133 m from <strong>the</strong> native marsh.The camera focal area for each site varied slightly, rangingfrom approximately 90 to 180 m 2 . Total bird usage(shorebird and waterfowl) from each tape was recordedevery 30 seconds and <strong>the</strong> data was converted to mean dailyflux densities (#/m 2 /hour). For shorebirds, daily fluxdensities were based only on time periods during <strong>the</strong> daywhen <strong>the</strong> tideflats were exposed. The total number <strong>of</strong> days <strong>of</strong>complete data collection, from February 18, 2003 to May 14,2003, ranged from 20 to 40 depending on <strong>the</strong> site. Visualobservation <strong>of</strong> bird usage in <strong>the</strong> winter <strong>of</strong> 2003/04 was doneusing a single observer. Three plots (one hectare each) persite were observed for 10 minute intervals using a spottingscope. Observations were timed to coincide with peak usageat each site, just prior to tidal submergence or after tidalwithdraw. Observation frequency was at least once a week.Bird species and behavior were noted.Soil and plant dataIntact cores to <strong>the</strong> bottom <strong>of</strong> <strong>the</strong> root system (80+ cm)were collected by digging a 1-m wide and deep trench.- 208 -