Behavioral Ecology Advance Access published online on March 7, 2008
Behavioral Ecology, doi:10.1093/beheco/arn029
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Mechanosensory function for facial ornamentation in the whiskered auklet, a crevice-dwelling seabird
Department of Biology, Memorial University, St John's, Newfoundland and Labrador, A1B 3X9, Canada
Address correspondence to S.S. Seneviratne. E-mail: sampath{at}mun.ca.
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Abstract |
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Sexual selection has been the prevalent explanation for the evolution of birds' elaborate feather ornaments. An overlooked possibility is that feather appendages arose due to a naturally selected sensory function involving sensitivity to pressure or touch to facilitate obstacle avoidance either in flight or on land. Here, we show experimentally that elongated facial feather adornments of whiskered auklets (Aethia pygmaea), a sexually monomorphic crevice-dwelling seabird, have a mechanosensory use for orientation in darkness underground. While navigating inside a lightproof maze simulating the structure and conditions of breeding crevices, whiskered auklets (n = 99) showed a 275% increase in frequency of head bumps in the absence of their protruding feather crest and facial plumes. A weak positive relationship (R = 0.36, P = 0.04) between natural crest length and the frequency of head bumps in the absence of the crest suggested that individuals with longer ornaments depend more on these traits for navigation in the wild. We hypothesize that protruding feathers evolved through a combination of natural selection for sensory function and sexual selection as known for other auklets. More widely, birds inhabiting cluttered environments would benefit from elongated facial plumage that mechanically detects obstacles.
Key words: Aethia, feather ornaments, mechanosensory function, sexual selection, whiskered auklet.
Received 27 September 2007; revised 26 January 2008; accepted 28 January 2008.