Vertical collision risk of Red-crowned Cranes at coastal onshore wind farms in eastern China.

BACKGROUND

With the continued expansion of coastal wind farms toward wetland edges, understanding the mechanisms that drive collision risk for large waterbirds around wind turbines is becoming increasingly important.

METHODS

Based on satellite tracking data from seven Red-crowned Cranes (Grus japonensis) in the coastal area of Yancheng, Jiangsu Province, and the geometric parameters of the wind turbine rotor-swept zone (RSZ), we developed a coupling framework linking crane flight heights with the vertical position of the RSZ. We used this framework to assess potential collision risk during the non-migratory period.

RESULTS

Crane flight height showed clear vertical overlap with the RSZ, but potential collision risk was not evenly distributed throughout the RSZ. Instead, risk was concentrated in several adjacent low to medium altitude bands. The 30-35 m band contributed the most, followed by the 35-40 m and 40-45 m bands. Simulations showed that increasing turbine hub-height could substantially reduce collision risk by shifting the RSZ upward as a whole. A 20 m increase in hub-height reduced overall risk by 48.9%.

DISCUSSION: Based on empirical flight height data, this study revealed the heterogeneous vertical distribution of potential collision risk for Red-crowned Cranes and the mechanisms underlying its formation. It also identified key risk height bands, providing a more mechanistic basis for turbine-design optimization, risk mitigation, and coordination between coastal wind power development and waterbird conservation.