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circannual rhythm

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Any biological rhythm involving a biological or psychological process that occurs or fluctuates at intervals of approximately one year, even in controlled environments from which seasonal cues have been eliminated, such as the seasonal changes in behaviour of some migratory birds, which persist even under constant laboratory conditions from which fluctuations in temperature, daylight, and other seasonal cues have been excluded. See also biological clock, chronobiology, Zeitgeber. Compare circadian rhythm, infradian rhythm, ultradian rhythm. [From Latin circa about + annus a year]

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