Mid-Atlantic Baseline Studies: Nocturnal Migration Monitoring

While oceans can act as barriers to migrating landbirds, including songbirds and raptors, many species also make long transoceanic flights, especially at night. We used two methods to document nocturnal migration over open waters in the mid-Atlantic: avian passive acoustics and weather surveillance radar.

For more information, see Chapters 26 and 27 in the technical report.

Many landbird species migrate at night and emit short species-specific vocalizations during flight. Nocturnal passive acoustic monitoring stations can record those flight calls and provide data on species presence and an index of migratory activity. In our study, a passive acoustic monitoring device was deployed on the survey vessel during nights spent on the water to detect flight calls of landbirds migrating through the study area, both to test the effectiveness of this method from a boat platform, and to obtain preliminary data about the species composition of nocturnal migrants in the offshore environment of the mid-Atlantic.

We analyzed weather surveillance radar (NEXRAD) to identify potential offshore migration pathways and timing, as well as environmental and temporal variables correlated with these patterns. Weather radars send microwaves into the atmosphere to detect precipitation. These microwaves also indicate the locations of flying animals, such as birds, bats, and insects. During migration, “blooms” of migratory activity can be seen surrounding radar units on unfiltered radar maps (in the header image, irregular green and yellow areas represent precipitation, while the more circular blue and gray areas are migratory activity). Innovations developed during this study allowed for targeted exclusion of meterological phenomena, greatly improving the sample size of available data and allowing for examination of migratory activity even during nights with precipitation, which had previously been impossible.

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• Delingat J, Bairlein F, Hedenström A (2008) Obligatory barrier crossing and adaptive fuel management in migratory birds: The case of the Atlantic crossing in Northern Wheatears (Oenanthe oenanthe). Behavioral Ecology and Sociobiology 62:1069–1078. doi: 10.1007/s00265-007-0534-8
• Evans WR (2012) Avian Acoustic Monitoring Study at the Maple Ridge Wind Project 2007-2008: Final Report (No. No. 12-23), Report prepared for the New York State Energy Research and Development Authority. New York State Energy Research and Development Authority