Staying in plastic containers interferes with the orientation of clock-shifted homing pigeons

Staying in plastic containers ventilated with natural air during transport and while waiting at the release site was found to affect the initial orientation of pigeons, Columba livia f. domestica, that were exposed to a 6-h clock-shift. The deflection from the mean direction of controls was significantly smaller, and the mean vector length was significantly shorter, than that of clock-shifted pigeons transported in conventional wooden cages. This effect was most pronounced when the birds stayed in plastic containers for the first and second time. Nonshifted control birds seemed to be largely unaffected by plastic containers. There was no influence on homing performance, which suggests a transient nature of the effect. Since the clock-shifted birds had access to the same orientational cues as the controls, we suggest that their sun compass was impaired by stress. We discuss general implications of this container effect, particularly in relation to some cases of olfactory deprivation where containers have been used and stress-induced side-effects cannot be excluded. Copyright 1999 The Association for the Study of Animal Behaviour.