Moonlight triggers nocturnal display in a diurnal bird.

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From: Animal Behaviour(Vol. 171)
Publisher: Elsevier B.V.
Document Type: Report
Length: 421 words

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Keywords African houbara bustard; Chlamydotis undulata fuertaventurae; lunar phase; moonlight; nocturnal display; vocalization Highlights * We used loggers with an accelerometer to record houbara bustards' nocturnal display. * Nocturnal booming intensity on full moon nights equalled peak diurnal intensity. * Moonlight allows nocturnal visual communication and copulation attempts. * Nocturnal booms are more redundant and informative than diurnal ones. * Males significantly increase their total display time by vocalizing at night. The importance of nocturnal display in diurnal birds has been neglected for a long time, owing to the difficulties in recording behaviour by night. Using loggers with an accelerometer (ACC) we studied nocturnal display in male African houbara bustards, Chlamydotis undulata, ssp. fuertaventurae. Diurnal display of male houbaras consists of a visual component, the display run, and an acoustic component, the boom. Nocturnal display runs were only recorded twice, both on full moon nights. Nocturnal booming intensity was highest on full moon nights when it reached similar levels to those during peak diurnal display at dawn. The more favourable physical conditions for sound transmission and the reduced acoustic competition with wind and other birds at night have been proposed to explain nocturnal vocalizing. Minimizing copulation disruptions, a frequent intramale competition mechanism in bustards, could be an additional advantage of nocturnal display. However, these factors do not explain why vocal activity is highest on full moon nights. We suggest that moonlight may help displaying males to detect predators, as well as to communicate visually with approaching females. Moonlight also allows males to combine booms with visual signals produced by the white neck feathers exposed during booming into more efficient multimodal signals. Moonlight would thus ultimately lead to males achieving nocturnal copulations, which indeed might be more frequent than previously thought, according to rates of nocturnal ACC-recorded precopulatory movements. Finally, nocturnal booming sequences had almost twice as many booms as diurnal ones, which suggests that nocturnal vocalizations transmit higher-quality information about signalling males than diurnal vocalizations. Nocturnal booming significantly increased the total display time of male houbara bustards; thus, future studies should investigate whether nocturnal vocal activity represents an important contribution to individual fitness in this and other nocturnally vocalizing diurnal species. Author Affiliation: Museo Nacional de Ciencias Naturales (CSIC), Departamento de Ecología Evolutiva, Madrid, Spain * Correspondence: J. C. Alonso, Museo Nacional de Ciencias Naturales (CSIC), José Gutiérrez Abascal 2, Madrid, E-28006, Spain. Article History: Received 27 February 2020; Revised 19 May 2020; Accepted 8 October 2020 (miscellaneous) MS. number: 20-00138R Byline: Juan C. Alonso [jcalonso@mncn.csic.es] (*), Inmaculada Abril-Colón, Carlos Palacín

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Gale Document Number: GALE|A648929888