Virginia marsh songbird rope-drag data – winter 2014

Bird species that are restricted to tidal marshes during one or all of their life stages are under increasing pressure from sea-level rise. To date, most of the research focused on this group has been conducted during the breeding season despite the fact that more than half of the annual cycle is spent on wintering grounds and the high likelihood that the winter period is the most critical time for adult survival. We used a double-pass rope-drag technique to estimate the winter abundance of sharp-tailed sparrows (Ammospiza nelson and A. caudacutus collectively), seaside sparrows (A. maritimus) and marsh wrens (Cistothorus palustris) within tidal marshes of Virginia along 102 60×250 m transects between January and March 2014. We used the first pass to remove birds from the transect and the second pass was used to estimate detection probabilities. The technique was highly effective producing detection rates of 98% for sharp-tailed sparrows, 95% for seaside sparrows, and 91% for marsh wren..., We used double-pass rope-drag transects to survey sparrows and wrens within marsh sites. Transects were 60m wide and their length varied from 200–250 m depending on the available space and placement within the marsh patch. The 60m rope (0.635 cm diameter) was weighted in the middle by two plastic containers filled with stones to create additional vegetation disturbance. A transect was surveyed at approx. 0.8 m/s-1 by three people where two were stationed on either end of the rope and the third walked <5 m behind the center of the rope. The third observer mapped the transect tracks to ensure that the survey was performed in a straight line. Once the entire transect length was surveyed (first pass) the observers immediately reversed direction to pass over the same area a second time (second pass) following the GPS track and observer footprints to ensure the exact same path was followed on the return pass. When birds were flushed, we recorded whether the bird landed within or outside th...,