Data for: Flying through gaps – How does a bird deal with the problem and what costs are there?

Animals flying in the wild often show remarkable abilities to negotiate obstacles and narrow openings in complex environments. Impressive as these abilities are, this must result in costs in terms of impaired flight performance. In this study, I used a budgerigar as model for studying these costs. The bird was filmed in stereo when flying through a wide range of gap widths from well above wingspan down to a mere 1/4 of wingspan. 3D flight trajectories were acquired and speed, wingbeat frequency and accelerations/decelerations were calculated. The bird used two different wing-postures to get through the gaps and could use very small safety margins (down to 6mm on either side) but preferred to use larger when gap width allowed. When gaps were smaller than wingspan flight speed was reduced with reducing gap width down to half for the smallest and wingbeat frequency was increased. I conclude that flying through gaps potentially comes with multiple types of cost to a bird of which the main may be: i) reduced flight speed increases the flight duration and hence the energy consumption to get from point A to B, ii) the underlying U-shaped speed to power relationship means further cost from reduced flight speed, and associated with it iii) elevated wingbeat frequency includes a third direct cost.Analysis of the coordinate files is done by running the matlab-script "Analyse_flights.m". It will allow the user to specify the files to analyse and will ask for the files (calibration file, frames to analyse and reference plate position) it needs in order to run analysis. All required files are included in the folders with the coordinates. The reference plate positions (called Plate points SX) contain three points on the calibration plate in horizontal orientation in the first frame and this will define the coordinate system to put it into real world. The Matlab file "Analyse_WT_distance.m" will run the calculations of the wing-tip distances using the same coordinates files as with the speed analysis. "Plot_all_speeds_over_time.m" will calculate accelerations and plot all together. See "Read Me.txt" for more details. Funding provided by: VetenskapsrådetCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100004359Award Number: 2018-04292Stereo filming and 3D trajectory calculations. The dataset contains digitized coordinates and the code included can be used to re-run all calculations that was done for during the analysis for the study