When pigeons in motion lose sight of their food: behaviour on visible displacement tasks revisited

Abstract

In traditional visible displacement tasks, animals view an object as it is moved out of their sight, but either the object moves behind an occluder or an occluder moves in front of it. Here we present a more ecologically realistic visible displacement task for pigeons ( Columba livia (Gmelin, 1789)) in which it was the animal that occluded the object, a food dish in this case, by virtue of its own motion. In a branched maze, pigeons had visual access to food, which they would lose from view as they moved through the maze. A within-subject design was used whereby the task was presented first in descending order of difficulty (i.e., decreasing memory load owing to the opening of (i) gaps and (ii) windows in the walls of the maze), and followed 10 months later by an ascending order. When the food was visible at all times through windows and gaps, pigeons would make turns in the maze that would bring them closer to the food (i.e., they chose the shortest route above chance levels). In general, they failed to do so when the food was lost from view, but there was one exception at the end of the study (the second time that there were gaps but no windows): there was a significant tendency for the last two turns that brought the bird out of the maze to be the shortest route to the food. The pigeons may have learned to take advantage of opportunities to lighten their memory load.