Approach-withdrawal behavior of peach-faced lovebirds, Agapornis roseicolis, and its modification by brain lesions.

Abstract

I. The frequency of mobbing vocalizations (chips, squeaks, chitters) and wing-beating was increased by the presence of a strange object (a small wooden cylinder) in the cage. The relative increase produced by the cylinder was much greater in birds that were partially isolated from the sounds as well as the sight of others than in birds only visually isolated. 2. The number of mobbing displays given by 20-hour food-deprived birds in response to the cylinders was sharply reduced by simultaneous presentation of food (even though the birds did not eat) but remained significantly above that given to food alone. This effect was observed in all lesioned birds as well as in intact controls. 3. A peculiar vocalization is described and termed singing because of some resemblance to subsong of passerines. It included all the vocalizations encountered in mobbing but occurred mostly in birds that appeared drowsy and was inhibited by stimuli that produced mobbing. 4. Brain lesions that destroyed the medial archistriatum bilaterally greatly reduced the frequency of mobbing displays in response to unfamiliar objects, and simultaneously decreased withdrawal and avoidance and increased some approach behavior. 5. Lesions of the hyperstriatum increased mobbing displays and probably increased the inhibitory effect of the cylinders on feeding compared to intact birds.