Fenthion as a secondary poisoning hazard to American kestrels

The potential of fenthion to act as a secondary poisoning hazard to birds of prey was investigated using American kestrels (Falco sparverius) and house sparrows (Passer domesticus) as a representative model of a naturally occurring predator-prey interaction. Kestrels were presented with live sparrows previously exposed to perches containing Rid-A-Bird 1100$ sp circler$ solution (Rid-A-Bird, Inc., Muscatine, IA), 11% fenthion active ingredient, under simulated field conditions. All 14 kestrels tested died following ingestion of fenthion-exposed sparrows. Decreased brain cholinesterase activity and residue analyses of kestrel gastro-intestinal samples confirmed secondary fenthion poisoning.Prey selection trials were conducted in the laboratory to determine the response of kestrels to a mixed flock of contaminated and uncontaminated sparrows. Kestrels captured fenthion-exposed prey significantly more often (12 out of 15 trials) than normal, unexposed prey.These results suggest that avian predators and scavengers in the wild are at risk from contact with fenthion-exposed prey in areas where Rid-A-Bird perches are in use