Supportive wind conditions influence offshore movements of Atlantic Coast Piping Plovers during fall migration

ABSTRACT In advance of large-scale development of offshore wind energy facilities throughout the U.S. Atlantic Outer Continental Shelf (OCS), information on the migratory ecology and routes of federally threatened Atlantic Coast Piping Plovers (Charadrius melodus melodus) is needed to conduct risk assessments pursuant to the Endangered Species Act. We tagged adult Piping Plovers (n = 150) with digitally coded VHF transmitters at 2 breeding areas within the southern New England region of the U.S. Atlantic coast from 2015 to 2017. We tracked their migratory departure flights using a regional automated telemetry network (n = 30 stations) extending across a portion of the U.S. Atlantic Bight region, a section of the U.S. Atlantic coast, and adjacent waters of the Atlantic Ocean extending from Cape Cod, Massachusetts, to Cape Hatteras, North Carolina. Most adults departed within a 10-day window from July 19 to July 29, migrated nocturnally, and over 75% of individuals departed within 3 hr of local sunset on evenings with supportive winds. Piping Plovers migrated offshore directly across the mid-Atlantic Bight, from breeding areas in southern New England to stopover sites spanning from New York to North Carolina, USA, over 800 km away. During offshore migratory flights, Piping Plovers flew at estimated mean speeds of 42 km hr–1 and altitudes of 288 m (range of model uncertainty: 36–1,031 m). This study provides new information on the timing, weather conditions, routes, and altitudes of Piping Plovers during fall migration. This information can be used in estimations of collision risk that could potentially result from the construction of offshore wind turbines under consideration across large areas of the U.S. Atlantic OCS. LAY SUMMARY The Atlantic coast population of the Piping Plover is listed as “Threatened” under the U.S. Endangered Species Act. Previously, little was known about exactly when, under what conditions, and along which routes these shorebirds undertake their migration from nesting areas along the Atlantic coast to wintering sites extending to eastern Caribbean islands. To help fill these information gaps, we attached miniature digitally coded VHF transmitters to 150 adult Piping Plovers at nesting areas in southern New England and constructed 35 radio antenna towers along the Atlantic coast to track their routes during fall migration. Most of the Piping Plovers in our study departed from southern New England in late July, at sunset, with tailwinds supporting offshore migratory flights across the mid-Atlantic Bight to stopover areas spanning from coastal New York to North Carolina. During offshore migratory flights, Piping Plovers flew at estimated mean speeds of 42 km hr–1 and at altitudes of 288 m. Our results provide the first empirical data on Piping Plover flight routes, altitudes, and weather conditions during fall migration. This information can be used to estimate collision risk from offshore wind turbines currently under consideration across large areas of the U.S. Atlantic Ocean.