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Sounds of Modified Flight Feathers Reliably Signal Danger in a Pigeon

2017; Elsevier BV; Volume: 27; Issue: 22 Linguagem: Inglês

10.1016/j.cub.2017.09.068

1879-0445

Trevor G. Murray, Jochen Zeil, Robert D. Magrath,

Animal Behavior and Reproduction

In his book on sexual selection, Darwin [1Darwin C. The Descent of Man and Selection in Relation to Sex.Princeton University Press, 1981 Edition. J. Murray, 1871Crossref Google Scholar] devoted equal space to non-vocal and vocal communication in birds. Since then, vocal communication has become a model for studies of neurobiology, learning, communication, evolution, and conservation [2Catchpole C.K. Slater P.J.B. Bird Song: Biological Themes and Variations. Cambridge University Press, 2008Crossref Scopus (271) Google Scholar, 3Marler P. Slabbekoorn H. Nature's Music: The Science of Birdsong. Elsevier, 2004Google Scholar]. In contrast, non-vocal "instrumental music," as Darwin called it, has only recently become subject to sustained inquiry [4Bostwick K.S. Mechanisms of feather sonation in Aves: unanticipated levels of diversity.Acta Zool. Sin. 2006; 52: 68-71Google Scholar, 5Clark C.J. Locomotion-induced sounds and sonations: mechanisms, communication function, and relationship with behavior.in: Suthers R.A. Fitch W.T. Vertebrate Sound Production and Acoustic Communication. Springer, 2016: 83-117Crossref Google Scholar]. In particular, outstanding work reveals how feathers, often highly modified, produce distinctive sounds [6Bostwick K.S. Prum R.O. Courting bird sings with stridulating wing feathers.Science. 2005; 309: 736Crossref PubMed Scopus (54) Google Scholar, 7Clark C.J. Elias D.O. Prum R.O. Aeroelastic flutter produces hummingbird feather songs.Science. 2011; 333: 1430-1433Crossref PubMed Scopus (47) Google Scholar, 8Clark C.J. Kirschel A.N.G. Hadjioannou L. Prum R.O. Smithornis broadbills produce loud wing song by aeroelastic flutter of medial primary wing feathers.J. Exp. Biol. 2016; 219: 1069-1075Crossref PubMed Scopus (14) Google Scholar, 9Niese R.L. Tobalske B.W. Specialized primary feathers produce tonal sounds during flight in rock pigeons (Columba livia).J. Exp. Biol. 2016; 219: 2173-2181Crossref PubMed Scopus (17) Google Scholar], and suggests that these sounds have evolved at least 70 times, in many orders [10Clark C.J. Prum R.O. Aeroelastic flutter of feathers, flight and the evolution of non-vocal communication in birds.J. Exp. Biol. 2015; 218: 3520-3527Crossref PubMed Scopus (23) Google Scholar]. It remains to be shown, however, that such sounds are signals used in communication. Here we show that crested pigeons (Ochyphaps lophotes) signal alarm with specially modified wing feathers. We used video and feather-removal experiments to demonstrate that the highly modified 8th primary wing feather (P8) produces a distinct note during each downstroke. The sound changes with wingbeat frequency, so that birds fleeing danger produce wing sounds with a higher tempo. Critically, a playback experiment revealed that only if P8 is present does the sound of escape flight signal danger. Our results therefore indicate, nearly 150 years after Darwin's book, that modified feathers can be used for non-vocal communication, and they reveal an intrinsically reliable alarm signal.