Shorebird migration ecology at Monomoy National Wildlife Refuge

• Main Author: Koch, Stephanie Lianne
• Format: Text
• Language: English
• Published: DigitalCommons@URI 2010
• Subjects: Wildlife Conservation|Ecology|Environmental science; Arenaria interpres; Calidris alpina
• Online Access: https://digitalcommons.uri.edu/dissertations/AAI3451844

Many species of shorebirds (Charadrii) are long-distance migrants that rely on disturbance-free stopover sites with abundant food. Adequate protection of stopover sites requires knowledge of migration chronology, effects of anthropogenic disturbances, and factors affecting habitat selection. We studied shorebird migration ecology at Monomoy National Wildlife Refuge (Refuge), Cape Cod, Massachusetts, one of the most important shorebird stopover sites in eastern North America. Our findings can be implemented by land managers in the future to maintain the integrity of this stopover site. In the first manuscript, we studied seasonal variation in shorebird abundance during migration and determined peak periods of human use. Peak shorebird densities during southward migration (48-52 shorebird-use-days ha-1 ) were approximately three to five times greater than northward migration (9-15 shorebird-use-days ha-1), but were similar between years. We detected 22 species, but six species accounted for 87% of all shorebirds detected. Two migration strategies emerged with species either exhibiting a rather short, distinct window of migration, or a protracted migration. We documented low density human use in both years (0.018 ±0.003 humans ha-1 in 2006 and 0.008 ±0.001 humans ha-1 in 2007). In the second manuscript, we determined shorebird flush distances (to pedestrians) and recommended buffer distances to reduce disturbance. We also examined effects of shellfishing activity on shorebird abundance. Smaller shorebird species generally had shorter flush distances compared to larger species. Age was the most influential variable; juveniles generally flushed at closer distances than adults. Recommended buffer distances ranged from 50 m for Dunlins (Calidris alpina) to over 200 m for Black-bellied Plovers (Pluvialis squatarola). American Oystercatchers ( Haematopus palliatus) and Ruddy Turnstones (Arenaria interpres ) were the only species whose densities were correlated (positively) with shellfishing. In the last manuscript, we examined the spatial distribution of shorebirds using mudflats at lower tides, and evaluated the importance of physical and biological variables in observed shorebird densities. All species exhibited clumped distributions which varied between years and between species. Habitat types (preference for mudflat over saltmarsh), water depth (generally presence of shallow water), and prey densities (especially annelids and horseshoe crab eggs) were all important variables influencing shorebird densities.