Debajyoti Karmaker

Julia Groening

Ingo Schiffner

Mandyam V. Srinivasan

Abstract

This study investigates how birds (Budgerigars; Melopsittacus undulatus) avoid mid-air collisions by seeking to understand how they identify obstacles and evaluate their threat levels, and to uncover the strategies that they use to avoid collisions with them. In a series of experiments, We presented individual flying birds with three different scenarios: (i) obstacle free flight; (ii) flight past a static mechanical bird; and (iii) flight past a mechanical bird with flapping wings. All experiments were conducted in a purpose-built flight tunnel and the flights were recorded with four synchronized high-speed video cameras. We found that the birds maintained different radial separations from the obstacle, depending on the level of threat that it posed. They consistently passed the mechanical bird at a greater distance when its wings were flapping. The results also suggest that the distance to the mechanical bird is gauged using cues based on optic flow when the wings are stationary, and cues based most likely on image size when the wings are flapping.