Wind estimation based on thermal soaring of birds.

Area of Science:

• Ecology
• Biophysics
• Atmospheric Science

Background:

• Bird flight performance is significantly influenced by atmospheric dynamics, particularly wind.
• Understanding wind conditions is crucial for studying bird movement ecology, aerodynamics, and flight strategies.

Purpose of the Study:

• To introduce a systematic method for evaluating wind speed and direction using high-frequency GPS data from bird-borne tags.
• To estimate wind and airspeeds during thermalling flight and provide error estimates for these measurements.

Main Methods:

• Utilized high-frequency GPS recordings from bird-borne tags during thermalling flight.
• Assumed fixed horizontal mean wind speed during short flight segments with constant turn angles.
• Employed a maximum-likelihood approach to estimate drift, wind, and airspeeds.

Main Results:

• Developed an accurate and unbiased method for estimating wind speed and direction from GPS data.
• Provided error estimates for GPS-derived wind speed measurements.
• Validated the approach against weather reanalysis data and independent estimates from pairs of birds.

Conclusions:

• The new method offers precise measurements of wind speed, vertical winds, and uplift structure, which are typically difficult to obtain.
• This approach will advance the understanding of atmospheric conditions, flight aerodynamics, and bird flight strategies.
• GPS-tracked animals can serve as a valuable tool for atmospheric data collection, benefiting ecological and environmental studies.