1988. The influence of Tric*hinella pseudospiralis infection on the behaviour of captive, nonbreeding American kestrels (Falco sparverius) . Can. J. Zool . 66: 1685 -1692.Trichinella pseudospiralis infections induced mild behavioural changes in the American kestrel host (Falco sparverius) within the first 5 days postinoculation, a period that corresponds to the adult phase of the infection. However, more severe effects on mobility were precipitated as the larvae migrated and became established in the musculature. The debilitation persisted for at least 5 weeks postinoculation and involved a reduction in exercising, flying, elevated perching, and preening, and was accompanied by an increase in the frequency of walking and floor perching. Such behavioural effects, attributable to the presence of muscle larvae, may reduce the competitive fitness of infected individuals. The muscle larvae were randomly distributed among various muscle groups. SAUMIER, M. D., RAU, M. E., et BIRD, D. M. 1988. The influence of Trichinella pseudospiralis infection on the behaviour of captive, nonbreeding American kestrels (Falco sparverius). Can. J. Zool. 66 : 1685 -1692. L'infection causee par Trichinella pseudospiralis se manifeste chez la Crecerelle d'Amerique (Falco sparverius) par delegers changements de comportement au cours des 5 premier jours apres l'inoculation; cette pkriode correspond ii la phase adulte de I'infection. Par ailleurs, la mobilite de l'h6te est nettement modifiee lorsque les larves du parasite migrent vers les muscles et s'y etablissent. Les oiseaux sont debilites durant au moins 5 semaines apres l'inoculation et on observe une reduction de la frequence d'exercice et de vol, du temps passe haut perch6 et du temps consacre au lissage des plumes, ainsi qu'une augmentation de la frequence de marche et du temps passe perche au sol. De tels changements de comportement, attribuables ii la presence de larves dans la musculature, peuvent diminuer la capacite de competition de l'oiseau. Les larves sont reparties au hasard dans les differents muscles.