The effects of cage volume and cage shape on the condition and behaviour of captive European starlings ( Sturnus vulgaris)

Abstract

Cage size is widely recognised as an important determinant of captive animal welfare, but in contrast, cage shape has received far less attention. Husbandry recommendations for flying birds state that cages should be long in shape because this allows greater potential for flight. However, so far no studies have investigated the impact of cage shape on the behaviour or welfare of captive flying birds. We measured the effects of cage size and shape on the condition and behaviour of captive wild-caught European starlings ( Sturnus vulgaris) using a 2 × 3 factorial design in which birds were individually housed for 1 week in cages of one of two volumes (either medium at 0.3 m 3 or large at 1 m 3), and one of three shapes (long with an aspect ratio (i.e. length/height) of 3.43), standard with an aspect ratio of 1.72 or tall with an aspect ratio of 0.86). We found effects of cage size and the interaction of cage size and shape on the behaviour and condition of birds. In interpreting the welfare implications of our results we focused on stereotypic behaviour as measured by incidence of somersaulting and a novel statistic that quantifies sequential dependencies in the birds’ locations within the cage. The lowest measures of stereotypic behaviour were recorded in the large cages and the medium long cage. Cage shape was more important in determining the quantity of stereotypic behaviour in the medium cages than the large cages. Our findings support the recommendation that starlings be housed in long-shaped cages.