Comparison of shorebird abundance and foraging rate estimates from footprints, fecal droppings and trail cameras

Accurate estimates of shorebird abundance and foraging rate are important for population monitoring and habitat quality assessment. Shorebird abundance and foraging rate are often estimated using footprints and fecal droppings as proxy measurements. However, the relationship between shorebird counts and these proxy measurements is not well described in the scientific literature. This study investigates how observations of footprints and fecal droppings compare to shorebird counts from time-lapse photos as a way of measuring foraging rate (droppings bird^-1 min^-1). Trail cameras successfully recorded fine-scale movement of large flocks of Western Sandpipers Calidris mauri during a migratory stopover period at Roberts Bank, BC, Canada, providing a viable method for shorebird observation in intertidal mudflats and other sensitive habitat. I found a strong positive linear relationship between density of fecal droppings and number of Western Sandpipers. There was a weak positive relationship between footprint coverage and counts, with footprints reaching 100% spatial cover when counts of Western Sandpipers exceeded 30. I found Western Sandpipers foraged on Roberts Bank at a rate of 0.4 droppings min^-1, similar to estimates previously reported in studies across the Fraser River Delta (0.5 droppings min^-1), which suggests fecal droppings provide a robust estimate of shorebird abundance and foraging rate.