Sounds of Modified Flight Feathers Reliably Signal Danger in a Pigeon Trevor G. Murray, Jochen Zeil, Robert D. Magrath  Current Biology  Volume 27, Issue 22, Pages 3520-3525.e4 (November 2017) DOI: 10.1016/j.cub.2017.09.068 Copyright © 2017 Elsevier Ltd Terms and Conditions

Current Biology 2017 27, 3520-3525.e4DOI: (10.1016/j.cub.2017.09.068) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 Wing Movement, Sound Production, and Feather Morphology (A and B) A single wingbeat cycle from the takeoff of a crested pigeon. Vertically aligned by time are separate frames of high-speed video (A) (Movie S1) and the spectrogram of wing sounds (B) (Audio S1). (C) The mean start and end time of each note in relation to the upstroke and downstroke during a single wingbeat. Error bars show 95% confidence intervals. (D) A crested pigeon wing with the outmost six primaries labeled. (E) The width of the outer six primary feathers of the crested pigeon and its eight closest relatives (CP, crested pigeon; see Figure S1 for further detail and other species’ names). Current Biology 2017 27, 3520-3525.e4DOI: (10.1016/j.cub.2017.09.068) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 2 The Effects of Feather Removal on Sound Production (A–C) Spectrograms of wing sounds produced under three experimental treatments: control, no feathers removed (A); P8, the 8th primary of each wing removed (B); and P9, 9th primaries removed (C). A spectrogram after P7 removal is not depicted. (D–F) Quantitative effects of treatments on sound produced. (D) The mean change in relative amplitude of the high note (high–low, dB), with the y axis centered on the mean of the control. (E and F) Mean tonality of the low note (E) and mean tonality of the high note (F). Bars show means with SE from a linear regression, and asterisks show significant differences from the control (∗ < 0.05; ∗∗ < 0.01; ∗∗∗ < 0.001). See Table S1 for summary statistics. Current Biology 2017 27, 3520-3525.e4DOI: (10.1016/j.cub.2017.09.068) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 3 Effects of Flight Type on the Acoustic Properties of Takeoff Sounds and Flight Performance (A–C) The mean difference during takeoff between escape and routine takeoffs in wingbeat frequency (A); linear acceleration (B); and tempo of the tonal note cycle (C). Asterisks highlight significant differences from the ANOVA (∗p < 0.05; ∗∗∗p < 0.001), and bars show SE. (D and E) The relationship between wingbeat frequency and tonal wing sound tempo (D), and linear acceleration across all takeoffs (E). Black lines represent the line of best fit from linear regression. Linear acceleration is the change in forward velocity during the first 0.5 s of the takeoff (see Figure S2). Current Biology 2017 27, 3520-3525.e4DOI: (10.1016/j.cub.2017.09.068) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 4 Proportion Fleeing to Cover after Playback of Wing Sounds The playbacks: Escape, a normal high-tempo escape takeoff; P8 Trim, high-tempo release takeoff with 8th primaries removed; P9 Trim, high-tempo release takeoff with 9th primaries removed; No Trim, a high-tempo release takeoff with no feathers removed; and Routine, a normal low-tempo routine takeoff. Bars are model predicted means (±SE) from binomial generalized linear mixed models. Asterisks show the significant difference (∗∗ < 0.01) in the key contrast of P8 and P9 removal. See Table S2 for summary statistics. Current Biology 2017 27, 3520-3525.e4DOI: (10.1016/j.cub.2017.09.068) Copyright © 2017 Elsevier Ltd Terms and Conditions