Sea Duck Ecology - Methods

Methods Summary

Study Areas

1. Chesapeake Bay (Pungoteague/Onancock Flats)
   1. Polyhaline (salinity ranging from 18-22 psu) area encompassing water depths ranging from 1-10 m that had discrete regions of muddy and sandy sediments (Fig. 1).
   2. Encompassed 102 km² in the vicinity of Onancock, Pungoteague and Nandua creeks.
2. Coastal Lagoon (Hog Island Bay)
   1. Coastal bay seaward of the Delmarva Peninsula that is a shallow, partially intertidal bay which lies between a barrier island to the east and the mainland to the west
   2. ~30 psu salinity and a diversity of fine-scale habitats ranging from intertidal flats and oyster reefs to deeper channels
   3. A diversity of discrete sediment types was also encountered.

 Sea Duck Distribution

• Vessel and fixed-wing surveys from November 2008 until the end of April 2009
• Locations recorded using a global positioning system (GPS)
• Abundance of surf scoters and long tailed ducks was enumerated for each aggregation

 Habitat Characteristics

• Benthic sampling based on sea duck aggregations from surveys
• Samples were collected using a Smith-McIntyre grab
• Sampled seabed to a depth of 10-15 cm, depending on sediment characteristics.
• Water depth was measured at the approximate centroid of each sampling and manually corrected to mean higher high water (MHHW) based on predicted vs. observed tides at appropriate reference stations.
• Percentage of organic matter and grain size analysis of sediment was determined from grabs.
• Sample washed on a 1-mm mesh sieve. Flora and fauna retained on this sieve were identified to the lowest practical taxonomic level for each individual grab.
• Bivalves, gastropods, fish and amphioxus (up to 50 per grab) were measured to the nearest mm in the organisms' longest dimension.
• Ash-free dry weight (i.e. dry tissue biomass) was determined.

Diet

• Limited number of LTDU and SUSC were haphazardly collected from groups observed to be foraging.
• Field necropsies were performed within ~30 min of collection.
• Several anatomical measurements were then taken.
• Esophagus from the bill to the gizzard (including the proventriculus) was removed with contents intact and preserved in 10% formalin.
• Gizzard was then removed and preserved separately.
• Macroflora and fauna from esophagus/proventriculus and gizzard samples were identified to the lowest practical taxonomic level for each bird.
• All bivalves, gastropods, fish and amphioxus were measured to the nearest mm in the organisms' longest dimension.
• Ash-free dry weight (i.e. dry tissue biomass) was determined.