Nocturnal Activity and Orientation Behavior During Spring Migration
and Early Summer in the Indigo Bunting, Passerina cyanea

Wiltschko, W., Wiltschko, R., Emlen, S.T. & Demong, N.J. (1980). In: Journal of Comparative Physiology, pp. 47-49.

Indigo Buntings (Passerina cyanea) that had been trapped in August were kept during the following months under photoperiodic conditions simulating the ones they would normally experience at that time of the year. From April 24 to June 16, their nocturnal activity and their directional tendencies were recorded. It was found that the activity, although it varied greatly from night to night, continued to be high until the termination of the registration period in mid June, whereas the orientation deteriorated at the end of May, i.e., after the end of the normal spring migration (Fig. 1, Table 1). Thus directed spring migratory restlessness and undirected "summer" restlessness seem to represent two separate phenomena. A possible adaptive significance of "summer" restlessness is discussed.