Wind as Driver of Bird and Bat Abundance, Flight Direction, Altitude, and Speed on the North Atlantic Shelf

TL;DR

This study combines radar and lidar data to analyze how wind influences bird and bat movement patterns at offshore wind sites, providing new insights into animal behavior relevant for collision risk assessment.

Contribution

It introduces a novel methodological framework for integrating radar and lidar data to study offshore bird and bat behavior in relation to wind conditions.

Findings

Wind influences animal presence, flight direction, altitude, and speed.

Smaller animals tend to align flight with wind and vary in altitude.

Larger animals fly in diverse directions at low altitudes.

Abstract

Quantifying the collision risk of birds and bats with offshore wind turbines requires an understanding of the drivers of flying animal behavior at offshore wind sites. An omnidirectional S-band radar system was deployed on a research barge on the Northeastern Shelf of the United States (40.9 deg N, 70.79 deg W) and collected data for a 5-week window during the 2024 autumn bird and bat migration. The barge also sup- ported two profiling lidar systems that measured the wind speed and direction. This study presents a first methodological approach for analyzing radar and lidar data together, providing a framework for future analyses of offshore bird and bat movements that can be used to improve collision risk models. Coupling the radar animal tracks with measured wind speed profiles revealed that wind is a driver of animal pres- ence, flight direction, flight height, and flight speed. Further, a hierarchical clustering methodology was developed to investigate behavior by approximate animal size. For example, smaller animals had con- centrated flight direction distributions aligned with the wind and flew at a variety of altitudes, whereas bigger animals flew in a wide variety of directions but were concentrated at low altitudes. Our results provide the first insights into animal behavior at offshore wind sites with paired radar and lidar data.