Deciphering choreographies of elaborate courtship displays of golden-collared manakins using markerless motion capture

摘要

Courtship displays are complex behaviours that evolve mainly through sexual selection. Males of golden-collared manakins (Manacus vitellinus) gather in leks and perform very elaborate courtship displays in forest courts to attract females. The rapid movements of the display, that involve acrobatic jumps between saplings, are challenging to record and investigate. Here we describe the use of a combination of tools to quantify the choreographies of manakin displays and reveal previously unknown aspects of the courtship. To test the prediction that aspects of male jump trajectories vary among males and may be subject to female choice, we evaluated whether parameters including take-off angle and velocity vary between individual males and displays. We used a custom-built synchronized camera system to record courtship displays in the field, under highly variable lighting conditions. We then used automatic image pattern recognition software to track the movements of the birds and extract three-dimensional (3D) coordinates of the birds' movements. After post-processing and cleaning of the raw 3D data, we compared automated and manually produced annotations to test the reliability of the 3D tracking methods. A subsequent analysis of tracked movements revealed that individual males performed their displays consistently across different recordings. We found that males express extreme values of force when they jump off saplings and the jump trajectory has a ballistic shape, confirming that no additional propulsion is provided by the wings. We also applied the analysis approach to non-jumping birds and found that they move at greater heights than jumping males. The acquired knowledge and the developed methods will allow us to compare different males in relation to courtship success in order to understand the role of choreographies in mate choice.