PT - JOURNAL ARTICLE AU - Martin Bulla AU - Mihai Valcu AU - Adriaan M. Dokter AU - Alexei G. Dondua AU - András Kosztolányi AU - Anne Rutten AU - Barbara Helm AU - Brett K. Sandercock AU - Bruce Casler AU - Bruno J. Ens AU - Caleb S. Spiegel AU - Chris J. Hassell AU - Clemens Küpper AU - Clive Minton AU - Daniel Burgas AU - David B. Lank AU - David C. Payer AU - Egor Y. Loktinov AU - Erica Nol AU - Eunbi Kwon AU - Fletcher Smith AU - H. River Gates AU - Hana Vitnerová AU - Hanna Prüter AU - James A. Johnson AU - James J. H. St Clair AU - Jean-François Lamarre AU - Jennie Rausch AU - Jeroen Reneerkens AU - Jesse R. Conklin AU - Joana Burger AU - Joe Liebezeit AU - Joël Bêty AU - Jonathan T. Coleman AU - Jordi Figuerola AU - Jos C. E. W. Hooijmeijer AU - José A. Alves AU - Joseph A. M. Smith AU - Karel Weidinger AU - Kari Koivula AU - Ken Gosbell AU - Larry Niles AU - Laura Koloski AU - Laura McKinnon AU - Libor Praus AU - Marcel Klaassen AU - Marie-Andrée Giroux AU - Martin Sládeček AU - Megan L. Boldenow AU - Michael Exo AU - Michael I. Goldstein AU - Miroslav šálek AU - Nathan Senner AU - Nelli Rönkä AU - Nicolas Lecomte AU - Olivier Gilg AU - Orsolya Vincze AU - Oscar W. Johnson AU - Paul A. Smith AU - Paul F. Woodard AU - Pavel S. Tomkovich AU - Phil Battley AU - Rebecca Bentzen AU - Richard B. Lanctot AU - Ron Porter AU - Sarah T. Saalfeld AU - Scott Freeman AU - Stephen C. Brown AU - Stephen Yezerinac AU - Tamás Székely AU - Tomás Montalvo AU - Theunis Piersma AU - Vanessa Loverti AU - Veli-Matti Pakanen AU - Wim Tijsen AU - Bart Kempenaers TI - Unexpected diversity in socially synchronized rhythms of shorebirds AID - 10.1101/084806 DP - 2016 Jan 01 TA - bioRxiv PG - 084806 4099 - http://biorxiv.org/content/early/2016/11/01/084806.short 4100 - http://biorxiv.org/content/early/2016/11/01/084806.full AB - The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment 1–4. Behavioural rhythms are well studied in isolated individuals under laboratory conditions1,5, but in free-living populations, individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6–10. Individuals can temporally segregate their daily activities (e.g. prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (e.g. group foraging, communal defence, pairs reproducing or caring for offspring)6–9,11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5–7,9. Here, we address this in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally-incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within–and between-species diversity in incubation rhythms. Between species, the median length of one parent’s incubation bout varied from one to 19 hours, while period length–the cycle of female and male probability to incubate–varied from six to 43 hours. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis had longer incubation bouts than those that are readily visible or actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less likely at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5–7,9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.