@article {Bulla084806, author = {Martin Bulla and Mihai Valcu and Adriaan M. Dokter and Alexei G. Dondua and Andr{\'a}s Kosztol{\'a}nyi and Anne Rutten and Barbara Helm and Brett K. Sandercock and Bruce Casler and Bruno J. Ens and Caleb S. Spiegel and Chris J. Hassell and Clemens K{\"u}pper and Clive Minton and Daniel Burgas and David B. Lank and David C. Payer and Egor Y. Loktinov and Erica Nol and Eunbi Kwon and Fletcher Smith and H. River Gates and Hana Vitnerov{\'a} and Hanna Pr{\"u}ter and James A. Johnson and James J. H. St Clair and Jean-Fran{\c c}ois Lamarre and Jennie Rausch and Jeroen Reneerkens and Jesse R. Conklin and Joana Burger and Joe Liebezeit and Jo{\"e}l B{\^e}ty and Jonathan T. Coleman and Jordi Figuerola and Jos C. E. W. Hooijmeijer and Jos{\'e} A. Alves and Joseph A. M. Smith and Karel Weidinger and Kari Koivula and Ken Gosbell and Klaus-Michael Exo and Larry Niles and Laura Koloski and Laura McKinnon and Libor Praus and Marcel Klaassen and Marie-Andr{\'e}e Giroux and Martin Sl{\'a}de{\v c}ek and Megan L. Boldenow and Michael I. Goldstein and Miroslav {\v s}{\'a}lek and Nathan Senner and Nelli R{\"o}nk{\"a} and Nicolas Lecomte and Olivier Gilg and Orsolya Vincze and Oscar W. Johnson and Paul A. Smith and Paul F. Woodard and Pavel S. Tomkovich and Phil F. Battley and Rebecca Bentzen and Richard B. Lanctot and Ron Porter and Sarah T. Saalfeld and Scott Freeman and Stephen C. Brown and Stephen Yezerinac and Tam{\'a}s Sz{\'e}kely and Tom{\'a}s Montalvo and Theunis Piersma and Vanessa Loverti and Veli-Matti Pakanen and Wim Tijsen and Bart Kempenaers}, title = {Unexpected diversity in socially synchronized rhythms of shorebirds}, elocation-id = {084806}, year = {2016}, doi = {10.1101/084806}, publisher = {Cold Spring Harbor Laboratory}, abstract = {The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1{\textendash}4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1,5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6{\textendash}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{\textendash}9,11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5{\textendash}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{\textendash} and between-species diversity in incubation rhythms. Between species, the median length of one parent{\textquoteright}s incubation bout varied from 1 {\textendash} 19 hours, while period length{\textendash}the time in which a parent{\textquoteright}s probability to incubate cycles once between its highest and lowest value {\textendash} varied from 6 {\textendash} 43 hours. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) 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 prevalent 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{\textendash}7,9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.}, URL = {https://www.biorxiv.org/content/early/2016/11/23/084806}, eprint = {https://www.biorxiv.org/content/early/2016/11/23/084806.full.pdf}, journal = {bioRxiv} }