Integrated vertical profiles for 16 coastal NEXRAD weather surveillance radars from 2014 to 2023

This dataset quantifies offshore and adjacent terrestrial migration of
landbirds along the western North Atlantic and Gulf of Mexico coasts from
2014–2023. Offshore flights of migratory landbirds are common but
difficult to quantify due to lack of offshore monitoring. Offshore wind
development is expanding rapidly and may overlap with migration corridors.
Understanding the timing, locations, and numbers of offshore birds can
identify high-risk periods and areas for collision mitigation. We used 16
coastal weather surveillance radars in the western North Atlantic and Gulf
of Mexico to evaluate differences in passage, altitude, and timing of
migration between adjacent terrestrial and offshore habitats for spring
and fall from 2014 to 2023. We used machine learning methods to predict
unobserved low altitude densities that the radar beam overshoots at
increasing distances from the radar. Migration traffic varied
geographically and seasonally, with offshore migration traffic being lower
in spring than fall and lower than terrestrial migration year-round.
Offshore migratory activity below 300m (common rotor-swept zones) showed
shorter durations and fewer peak nights than terrestrial migration.
Offshore flight altitudes were 8-14% lower than over land, and the
propensity for offshore flights was higher in fall, especially near
coastlines perpendicular to migratory directions. We identify regional
patterns in offshore migration to inform wind energy siting decisions and
operation. Migration of landbirds in the offshore environment at rotor
swept zones is common, and increasing wind energy operations will likely
increase interaction between birds and rotors. The limited number of peak
nights and shorter migration windows offshore increases opportunities for
dynamic conservation. Curtailment targeting high-risk regions, seasons and
nights, will reduce operational downtime while protecting birds. Fall
migration and areas downstream of coastlines perpendicular to migratory
direction have a higher propensity for offshore migration, suggesting that
spatial and temporal variation in migration intensity should be considered
when balancing collisions risks and operational costs.