Effects of aviary and box sizes on body mass and behaviour of domesticated budgerigars (Melopsittacus undulatus)
Forty-eight budgerigars (Melopsittacus undulatus) were pairwise housed in small (80 × 40 × 50 cm) and large (160 × 40 × 50 cm) (length × breadth × height) boxes, as well as in 2.0 × 1.0 × 2.0 m aviaries. All boxes and aviaries had
two or three (aviaries) perches and food was offered on the bottom. The body masses of female budgerigars increased significantly when they were housed in boxes instead of aviaries. The size of the box did not influence body mass. The frequency of flying was adjusted to the size of the box
as both males and females flew approximately twice as often from perch to perch in a small box than in a large box of double length. Flying behaviour differed significantly between large and small boxes and aviaries. The ratio of invariantly flying from perch to perch to all flying events
increased from aviaries < large boxes < small boxes. About 75% of all flying events in small boxes consisted of flying from perch to perch. Females in boxes spent more time on the bottom where the food was placed than females in aviaries. Both the significant body mass gain in female
budgerigars, as well as the invariant, stereotypic flying movements, indicated reduced welfare in budgerigars housed in boxes, compared with those in aviaries. Providing a large box did not prevent body mass gain, but did increase the variation in flying patterns. Under long-term housing conditions,
boxes could lead to at least two serious welfare problems; obesity and stereotypic behaviour, and should be avoided for budgerigars. Therefore, aviary housing should be chosen wherever possible.