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The vibrational sensitivity of awake pigeons was tested with the heart rate conditioning method. This method proved to be a very sensitive instrument for the behavioural measurement of the pigeon's sensitivity to mechanical stimuli.Sine wave vibrational stimuli between 50 and 2000 Hz were applied to the 1st, 7th and 16th primary feathers of the wing. The resulting threshold curves were U-or V-shaped with 3 characteristics: (i) The frequency of best response was either 800 or 900 Hz. (ii) Within the broad frequency range of vibrational sensitivity (50 to 2000 Hz) the sensitivity was extremely high at the best frequency: threshold amplitudes lay between 0.5 and 0.09 ~tm. (iii) The threshold curves showed very sharp tuning at best frequency with bandwidths between 0.3 and 0.7 octaves (measured at best frequency 10fold above threshold). The functional meaning of the characteristic vibrational sensitivity of the wing for flight control is discussed; it is interpreted as an adaptation to special situations occurring during flight.

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