Assessing anthropogenic disturbances to develop buffer zones for shorebirds using a stopover site

Abstract

ABSTRACTAnthropogenic disturbance can degrade the quality of stopover sites for migratory shorebirds. We investigated the potential effects of pedestrian traffic and shellfishing on foraging shorebirds at a key stopover site at Monomoy National Wildlife Refuge (Monomoy Refuge), Massachusetts, USA. We experimentally approached 11 species of shorebirds to quantify flight‐initiation distances (FID) and found that species and age affected FID. Smaller Calidris sandpipers generally allowed pedestrians to approach within 25 m before flushing, whereas larger shorebirds (black‐bellied plover [Pluvialis squatarola] and American oystercatcher [Haematopus palliatus]) had FID over 50 m. We also found that juveniles of all species had shorter FID than adults. Based on adult FID, we developed species‐specific buffer distances for 11 species that ranged from 61 m for least sandpiper (Calidris minutilla) to 186 m for black‐bellied plover. We also investigated the potential impacts of commercial and recreational shellfish harvesters, who rake for soft‐shell clams (Mya arenaria) on mudflats where shorebirds actively foraged. Microhabitats with recent shellfishing activity had a positive influence on the density of 2 species (ruddy turnstone [Arenaria interpres], and American oystercatcher), whereas the presence of shellfishers did not appear to affect the density of other species of shorebird we monitored. We regularly detected black‐bellied plovers and ruddy turnstones actively foraging in microhabitats where shellfishers had recently exposed sediment. Given the levels of shellfishing and pedestrian traffic at Monomoy Refuge, we found no evidence to suggest that current human activity has a strong negative impact on migratory shorebirds using Monomoy Refuge. However, if the amount of pedestrian traffic and shellfishing were to increase substantially, a buffer zone system might have to be implemented during peak migration periods to minimize impacts, with buffers >185 m from key foraging sites to reduce disturbance to the most sensitive species. © 2013 The Wildlife Society