Torpor in an andean hummingbird: its ecological significance.
Field studies on an Andean hummingbird showed that nocturnal torpor occurs more frequently and lasts longer in the winter. Energy depletion does not seem to cause this yearly torpor cycle, and a photoperiodically controlled rhythm that enables the birds to automatically conserve energy in early evening for possible metabolic expenditures required later in the winter night is suggested.
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