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 orien tation of pigeons, Columba livia f. domestica, that were exposed to a 6-h c lock-shift. The deflection from the mean direction of controls was signific antly smaller, and the mean vector length was significantly shorter, than t hat of clock-shifted pigeons transported in conventional wooden cages. This effect was most pronounced when the birds stayed in plastic containers fbr the first and second time. Nonshifted control birds seemed to be largely u naffected by plastic containers. There was no influence on homing performan ce, which suggests a transient nature of the effect. Since the clock-shifte d birds had access to the same orientational cues as the controls, we sugge st that their sun compass was impaired by stress. We discuss general implic ations of this container effect, particularly in relation to some cases of olfactory deprivation where containers have been used and stress-induced si de-effects cannot be excluded. (C) 1999 The Association for the Study of An imal Behaviour.