Comparing bird and human soaring strategies

TL;DR

This study compares the thermalling strategies of birds and humans, revealing shared features and suggesting that falcons use a formula similar to glider pilots for optimizing thermal use.

Contribution

It provides the first detailed comparison of bird and human thermalling strategies using high-resolution tracking data, highlighting common optimization features.

Findings

Birds and humans share similar thermalling behaviors.

Falcons appear to use a formula akin to the MacCready for thermal optimization.

Shared strategies suggest convergent solutions to energy-efficient soaring.

Abstract

Gliding saves much energy, and to make large distances using only this form of flight represents a great challenge for both birds and people. The solution is to make use of the so-called thermals, which are localized, warmer regions in the atmosphere moving upwards with a speed exceeding the descent rate of bird and plane. Whereas birds use this technique mainly for foraging, humans do it as a sporting activity. Thermalling involves efficient optimization including the skilful localization of thermals, trying to guess the most favorable route, estimating the best descending rate, etc. In this study, we address the question whether there are any analogies between the solutions birds and humans find to handle the above task. High-resolution track logs were taken from thermalling falcons and paraglider pilots to determine the essential parameters of the flight patterns. We find that there are relevant common features in the ways birds and humans use thermals. In particular, falcons seem to reproduce the MacCready formula widely used by gliders to calculate the best slope to take before an upcoming thermal.