title: Free and forced diving in birds.
abstract: Heart rates were measured during free and forced diving on each of two species of aquatic birds: the double-crested cormorant (Phalacrocorax auritus), a true diver, and the Canada goose (Branta candensis), a bottom feeder in shallow water. When they immersed voluntarily they showed no bradycardia, but when the same birds were forcibly held under water there was a rapid drop in heart rate to well below that at rest. This decrease indicates that ther may be a large component of emotional stress in the heart rate records from previous diving studies where restrained animals were forcibly submerged.
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D004242:Diving; D006339:Heart Rate; D006801:Humans; D013315:Stress, Psychological / Q000502:physiology; D013686:Telemetry