The effect of human disturbance on shorebird distribution at a critical stopover area on New Jersey’s Atlantic coast, USA

Shorebird populations in North America are experiencing worrisome rates of decline, with 93% of shorebird species showing negative trends in abundance during 1980–2019. These declines are attributed mainly to habitat loss, decreases in food availability (e.g. American Horseshoe Crab Limulus polyphemus eggs), and climate change. Human disturbance at migratory stopover sites may exacerbate the effects of these major threats by affecting rates of mass gain and patterns of space use by shorebirds. We recorded the abundance and behavior of migratory shorebirds at critical barrier island staging sites surrounding Little Egg Inlet on the New Jersey Atlantic Coast, and the impacts of human activities on shorebird abundance and distribution in the study area. We found that increased human activity was associated with a significant decrease in shorebird abundance and that humans and shorebirds preferred to use the same areas of the beach. Certain human activities tended to cause more disturbance than others, mainly motorized watersports and people walking, suggesting that shorebirds find some human behaviors more immediately threatening than others. We recorded a distinct second peak, in mid-October, in Red Knot Calidris canutus abundance. Based on our results, we recommend keeping staging sites in our study area seasonally closed to the public from April 1 through November 1 (instead of September 1) when the bulk of shorebird migration has passed.