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Video 9.3A: This movie shows the explosive eversion of the male duck penis in air. The male is threading on top of a female. The male cloaca is seen on the top left. The high-speed video is 250 frames/second and the entire eversion of the 20 cm penis occurs in 0.35 sec. (From Brennan et al. 2009).
Video 9.3B: This movie shows 6 clips of the eversion of the male duck penis everting in mechanical barriers. The first 2 clips show penis eversion in a straight tube and a counterclockwise spiral where eversion is unimpeded. The next two clips show eversion into mechanical barriers that mimic the female genitalia: one is a clockwise spiral, the other a 135º angle. In both of these, penis eversion is completely blocked. The last 2 clips show eversion into mechanical barriers made out of silicone. The first one is a counterclockwise spiral, where the penis everts unimpeded, the last one is a clockwise spiral where the penis breaks the silicone when it encounters resistance. The high-speed video is 250 frames/second. (From Brennan et al. 2009).
Source: Patricia L. R. Brennan, Christopher J. Clark, Richard O. Prum. Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Published December 23, 2009. DOI: 10.1098/rspb.2009.2139
Textbook Reference: Sexual Arms Races, p. 349