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When a year takes 18 months: Evidence for a strong circannual clock in a shorebird



When a year takes 18 months: Evidence for a strong circannual clock in a shorebird



Naturwissenschaften 89(6): 278-279



During the last three of 20 years kept as a pet, a red knot (Calidris canutus) went through two complete 'circannual' cycles of body mass and plumage. With a record cycle length of 18 months, this individual shorebird provides evidence for an exceptionally strong circannual clock system. The absence of synchronisation to outdoor but visible periodic cues suggests that the constant, socially-induced, day-night environment was of overriding importance. So far, only for songbirds is there firm experimental evidence that annual cycles are orchestrated by an endogenous circannual clock system. In constant environments the circannual cycles of these passerines tend to have periods that are shorter, rather than longer, than a year.

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Accession: 011651788

Download citation: RISBibTeXText

PMID: 12146795

DOI: 10.1007/s00114-002-0325-z


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