When the sun never sets: diverse activity rhythms under continuous daylight in free-living arctic-breeding birds

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: Kamiel Spoelstra, Martin Wikelski, Barbara Helm, Bart Kempenaers, Silke S. Steiger, Mihai Valcu
• Other Authors: Animal Ecology (AnE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2013
• Subjects: international; circadian clock; continuous daylight; mating system; arrhythmic activity; Arctic; Calidris; 14; 60; 70; Research Articles; General Biochemistry; Genetics and Molecular Biology; General Immunology and Microbiology; General Agricultural and Biological Sciences; General Environmental Science; General Medicine; envir; geo; Barrow; Alaska
• Online Access: http://eprints.gla.ac.uk/79859/1/79859.pdf; https://www.rug.nl/research/portal/files/62479630/20131016.full.pdf; https://pure.knaw.nl/portal/files/1697072/2013_Spoelstra_ProcRoySoc.pdf; https://doi.org/10.1098/rspb.2013.1016; http://www.scopus.com/inward/record.url?eid=2-s2.0-84893019727&partnerID=MN8TOARS; https://pure.knaw.nl/portal/en/publications/8d0a445d-43a2-42b4-b4c8-d41cb6b515e9; http://europepmc.org/articles/PMC3712422; https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2013.1016; https://royalsocietypublishing.org/doi/full-xml/10.1098/rspb.2013.1016; https://royalsocietypublishing.org/doi/10.1098/rspb.2013.1016; https://www.ncbi.nlm.nih.gov/pubmed/23782884; https://europepmc.org/article/MED/23782884; http://core.ac.uk/display/16458857; https://pure.mpg.de/pubman/faces/ViewItemOverviewPage.jsp?itemId=item_2165956; http://pubman.mpdl.mpg.de/pubman/item/escidoc:2165956; http://eprints.gla.ac.uk/79859/; https://kops.uni-konstanz.de/handle/123456789/38231; https://www.rug.nl/research/portal/publications/when-the-sun-never-sets(af942c23-5e6f-46ca-99b3-7ee32bd82446).html; https://pure.knaw.nl/portal/en/publications/when-the-sun-never-sets-diverse-activity-rhythms-under-continuous; https://rspb.royalsocietypublishing.org/content/280/1764/20131016?ijkey=237f423857380d06e47cdce3c4bf1af7e4a9d0e6&keytype2=tf_ipsecsha; https://paperity.org/p/49480778/when-the-sun-never-sets-diverse-activity-rhythms-under-continuous-daylight-in-free-living; https://www.narcis.nl/publication/RecordID/oai%3Apure.knaw.nl%3Apublications%2F8d0a445d-43a2-42b4-b4c8-d41cb6b515e9; https://academic.microsoft.com/#/detail/2052099282

Circadian clocks are centrally involved in the regulation of daily behavioural and physiological processes. These clocks are synchronized to the 24 h day by external cues ( Zeitgeber ), the most important of which is the light–dark cycle. In polar environments, however, the strength of the Zeitgeber is greatly reduced around the summer and winter solstices (continuous daylight or continuous darkness). How animals time their behaviour under such conditions has rarely been studied in the wild. Using a radio-telemetry-based system, we investigated daily activity rhythms under continuous daylight in Barrow, Alaska, throughout the breeding season in four bird species that differ in mating system and parental behaviour. We found substantial diversity in daily activity rhythms depending on species, sex and breeding stage. Individuals exhibited either robust, entrained 24 h activity cycles, were continuously active (arrhythmic) or showed ‘free-running’ activity cycles. In semipalmated sandpipers, a shorebird with biparental incubation, we show that the free-running rhythm is synchronized between pair mates. The diversity of diel time-keeping under continuous daylight emphasizes the plasticity of the circadian system, and the importance of the social and life-history context. Our results support the idea that circadian behaviour can be adaptively modified to enable species-specific time-keeping under polar conditions.