Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization 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 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. 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 who 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 captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.</p

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 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, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms 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 1–19 h, whereas period length—the time in which a parent’s probability to incubate cycles once between its highest and lowest value—varied from 6–43 h. 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 who 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, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms

Supporting Information for 'Unexpected diversity in socially synchronized rhythms of shorebirds'

Comparative stud

Unexpected diversity in socially synchronized rhythms of shorebirds

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Supplementary Data 3 - Study sites: location, population wing length, monitoring method, tide

------------------------------------------------------------------------------------------------------<br>Description of the dataset "Supplementary Data 3 - Study sites.csv"<br>--------------------------------------------------------------------------------------------------------<br> The dataset <br>    - is used in the paper "Unexpected diversity in socially synchronized rhythms of shorebirds" Nature 2016 by M. Bulla et al<br>    - contains estimates of mean female and male wing length for each population of biparental shorebirds from a specific study site, plus the locations of the study site, whether the locations had tide, and whether the tide was used by the population for foraging, and how the incubation was monitored.<br>--------------------------------------------------------------------------------------------------------<br> Questions can be directed to: Martin Bulla ([email protected])<br>--------------------------------------------------------------------------------------------------------<br> Values are separated by comma. <br>--------------------------------------------------------------------------------------------------------<br> 1. scinam            : scientific name of the species<br> 2. sp                 : four letter abbreviation of the species's English name<br> 3. study_site             : name of the study site<br> 4. site_abbreviation         : four letter abbreviation of the study site<br> 5. type            : was the study site at the breeding ground (breeding) or not (wintering)<br> 6. lat                : latitude of the study site (decimal)<br> 7. lon                : longitude of the study site (decimal)<br> 8. tidal_habitat             : is the study site at primarily tidal habitat (y=yes, n=no)<br> 9. tidal_used                : if the study site is at primarily tidal habitat, do the birds use it for foraging (y=yes, n=no)<br>10. incubation_monitoring    : method used to monitor incubation (for details see the paper's Extended Data Table 4)<br>11. sexing_method             : identifies the method used to sex individuals to estimate the mean female and male wing length<br>12. pop_wing_f          : mean female wing length for the population<br>13. f_wing_N                  : sample size used for the female mean estimate<br>14. pop_wing_m           : mean male wing length for the population<br>15. m_wing_N              : sample size used for the male mean estimate<br>16. data_source         : is the mean wing estimate based on the primary data ("our primary data") or literature (citation))<br><br>--------------------------------------------------------------------------------------------------------<br><br>WHEN USING THIS DATA, PLEASE CITE:<br><br>Bulla et al (2016). Supplementary Data 3 - Study sites: location, population wing length, monitoring method, tide. <br>    figshare. https://doi.org/10.6084/m9.figshare.1536260. Retrieved ADD DATETIME.<br><br>-------------------------------------------------------------------------------------------------------

Supplementary Data 3 - Study sites: location, population wing length, monitoring method, tide

------------------------------------------------------------------------------------------------------ Description of the dataset "Supplementary Data 3 - Study sites.csv" -------------------------------------------------------------------------------------------------------- The dataset - is used in the paper "Unexpected diversity in socially synchronized rhythms of shorebirds" Nature 2016 by M. Bulla et al - contains estimates of mean female and male wing length for each population of biparental shorebirds from a specific study site, plus the locations of the study site, whether the locations had tide, and whether the tide was used by the population for foraging, and how the incubation was monitored. -------------------------------------------------------------------------------------------------------- Questions can be directed to: Martin Bulla ([email protected]) -------------------------------------------------------------------------------------------------------- Values are separated by comma. -------------------------------------------------------------------------------------------------------- 1. scinam : scientific name of the species 2. sp : four letter abbreviation of the species's English name 3. study_site : name of the study site 4. site_abbreviation : four letter abbreviation of the study site 5. type : was the study site at the breeding ground (breeding) or not (wintering) 6. lat : latitude of the study site (decimal) 7. lon : longitude of the study site (decimal) 8. tidal_habitat : is the study site at primarily tidal habitat (y=yes, n=no) 9. tidal_used : if the study site is at primarily tidal habitat, do the birds use it for foraging (y=yes, n=no) 10. incubation_monitoring : method used to monitor incubation (for details see the paper's Extended Data Table 4) 11. sexing_method : identifies the method used to sex individuals to estimate the mean female and male wing length 12. pop_wing_f : mean female wing length for the population 13. f_wing_N : sample size used for the female mean estimate 14. pop_wing_m : mean male wing length for the population 15. m_wing_N : sample size used for the male mean estimate 16. data_source : is the mean wing estimate based on the primary data ("our primary data") or literature (citation)) -------------------------------------------------------------------------------------------------------- WHEN USING THIS DATA, PLEASE CITE: Bulla et al (2016). Supplementary Data 3 - Study sites: location, population wing length, monitoring method, tide. figshare. https://doi.org/10.6084/m9.figshare.1536260. Retrieved ADD DATETIME. -------------------------------------------------------------------------------------------------------