This data file describes motor and acoustic display parameters and body mass index of male blue-black grassquits. The data were collected by Lilian T. Manica, Regina H. Macedo, Jeff Graves and Jeff Podos. Column headings #bird: male identity #bmi: body mass index, calculated as the ratio between body mass (g) and tarsus length (mm) #song_duration: song duration (s) #freq_band: frequency bandwidth (Hz) #heightNS: leap height (mm), extracted from normal speed videos. See Figure 1 for illustration of measurement. #rotationNS: forward body rotation angle (degrees), extracted from normal speed videos. See Figure 1 for illustration of measurement. #display_rateNS: sum of leap displays plus perched vocalizations divided by the cumulative duration of focal observation (displays/min), extracted from normal speed videos. #p_leap_displayNS: proportion of leap displays relative to total displays (leap displays plus perched vocalizations), extracted from normal speed videos. #heightHS: leap height (mm), extracted from high speed videos. See Figure 1 for illustration of measurement. #rotationHS: forward body rotation angle (degrees), extracted from high speed videos. See Figure 1 for illustration of measurement. #leap_durationHS: time interval between the frame wherein the bird left the perch and the frame in which he touched it again with both feet (s), extracted from high speed videos. #leap_rateHS: number of leap displays executed divided by the cumulative leap display bout duration (one bout = observed sequences of two or more displays). #wing_beatsHS: average number of up and down wing flaps after the bird left the perch and before he touched it again with both feet, extracted from high speed videos. #velocityHS: leap display launch velocity (mm/s), calculated as the distance traversed by the beak between the frame wherein the bird left the perch and the frame wherein the first wing downstroke was completed, divided by the time interval between these two frames. Missing data are presented as ÒNAÓ. Note that bmi, rotationNS, p_leap_displayNS, heightHS and leap_durationHS were transformed for data analyses, when necessary, and one bmi outlier excluded from heightNS models. All variables were centered to zero and scaled by their standard deviation for data analyses.