Decline of salt marsh-nesting birds within the lower Chesapeake Bay (1992-2021)

A survey was conducted of a network of patches (N = 186) within tidal salt marshes located in the lower Chesapeake Bay (1992, 2021) for 12 species of breeding birds to evaluate trends in occupancy and abundance. The data includes 13 tables: Marsh Patch (patch codes and dates), Point Locations, and tables for the 11 surveyed species.

Methods
Plots were considered for inclusion if they were dominated (>90%) by and contained all of the plant forms including smooth cordgrass (≥30%), black needlerush (≥20%), salt meadow hay and salt grass combined (≥15%) and groundsel tree (≥10%). Four replicate patches were randomly selected for each size category from a pool of marshes that met criteria.

Birds were surveyed within 30-m fixed radius plots using a call-response technique. The call-response survey consisted of a 5-min sequence of alternating silent listening periods and species recordings in the following order; 1) 30 sec of silence; 2) 50 sec of black rail advertising call; 3) 10 sec of silence; 4) 50 sec of Virginia rail advertising call; 5) 10 sec of silence; 6) 50 sec of clapper rail advertising call; 7) 10 sec of silence; 8) 50 sec of king rail advertising call; 9) 40 sec of silence. Although black and king rails were never detected during either survey period, the playback sequence was maintained for consistency. Counts were executed by standing at the plot center and recording birds seen or heard during the playback sequence.