Changing air density affects flight costs in low-flying birds

Data and code supporting the findings of the study:  For details about the attributes in the data files please see the "README.txt" file. Code included in the study: The R script:"Shepard et al_Changing_air_density_affects_flight_costs_in_low_flying birds.R" is used to run the statistical tests and models presented in the study. The R script: "Shepard et al_density matters at sea level_script_DensityAltitudeEstimation.R" , is used to estimate Density altitude based on the air density over the ocean downloaded from the ERA5 monthly means global re-analysis. For details please see the supplementary information of the study.