The Importance of Survey Timing on Shorebird Density Estimates at East Bay, Nunavut, Canada

The Importance of Survey Timing on Shorebird Density Estimates at East Bay, Nunavut, Canada.  Melanie Dickie, Paul A. Smith and H. Grant Gilchrist.  Waterbirds 37(4): 394-401.  Waterbirds is an International journal, publishing new information on shorebirds and promoting new data on waterbirds from around the world.  In the December 2104 issue, this study examined the timing of breeding on counts of five shorebird species during transect surveys at East Bay, Nunavut, Canada, from 2000 to 2010. The species were: Black-bellied Plover (Pluvialis squatarola), Semipalmated Plover (Charadrius semipalmatus), Ruddy Turnstone (Arenaria interpres), White-rumped Sandpiper (Calidris fuscicollis) and Red Phalarope (Phalaropus fulicarius). Transect counts varied widely among species and years, and transect counts were most strongly predicted by the density of nests found during more intensive surveys. However, after accounting for this variation, survey counts were influenced substantially by survey timing. Surveys carried out shortly after the median date of nest initiation (∼2 days after) corresponded most closely to the densities of found nests, and if surveys were not within several days of the median date, the discrepancy between the two estimates was large. Although neither nest densities nor transect surveys are believed to be a perfect indication of local population status, these results suggest that the nearly inevitable variation in survey timing could introduce substantial bias into density estimates.