A comparison was made of the behaviour of budgerigars housed singly in commercially available cages obtained from a pet supplier, and budgerigars housed in a group of six in a small aviary. Budgerigars housed in the aviary consumed significantly more food and were more active, performing
more wing stretching and flying. Caged budgerigars performed significantly more vocalizations. When tested individually, aviary birds were more active in a novel test chamber and were significantly more likely to approach an unfamiliar bird. Cage birds were generally reluctant to approach
an unfamiliar bird, but showed an increasing tendency to approach when allowed a longer period of familiarization. Pet budgerigars are commonly housed in isolation from conspecifics, with little consideration of potential effects on welfare. The aim of this study was to provide some initial
information about the effects of social isolation on the behaviour of budgerigars.