Reverse turning and angle compensation in a migratory passerine, passerculus sandwichensis

Abstract

Reverse turning behaviour was revealed in the savannah sparrow ( Passerculus sandwichensis), a migratory passerine, using a T-shaped runway system. Compensatory reverse turns were recorded for experimental birds which were forced to make 90° turns either to the left or right before proceeding to a choice point. Controls ran a straight runway from start to choice point and were as likely to turn left as right. A second experiment revealed an ability to compensate for angular deviations in course. Experimentals were forced to make turns of less than 90° before entering a semi-circular arena. They responded with a compensatory turn of the appropriate sign (left or right) and magnitude. An idiothetic mechanism is probably involved in the observed angle sense (Winkelsinn). The results are broadly relevant to animal orientation.