Abstract
Parasitism is a hostile relationship that helps greatly in the development and evolution of many creatures in their race for survival. Chewing lice of nestlings of the osprey Pandion haliaetus (L.) have been studied in Farasan Island, Saudi Arabia. All previous chewing lice records from this bird have also been reviewed. Four species of chewing lice are previously known to infest P. haliaetus. The nestlings of the osprey in Farasan were only infested by Colpocephalum turbinatum Denny, 1842. This species of chewing lice is recorded herein for the first time from the Kingdom of Saudi Arabia and its distributional pattern is very characteristic among three different avian orders (Accipitriformes, Columbiformes, and Strigiformes). Colpocephalum turbinatum was found mainly on terrestrial birds of the order Columbiformes and it may be transferred to predatory birds in the other two orders, but the presence of this parasite on some aquatic birds of prey like osprey may indicate that the ancestors of these birds were terrestrial hunters that acquired this louse from their prey such as doves and pigeons before their transference to aquatic life. The pattern of chewing lice distribution through their host populations and habitats may reveal some important ecological and evolutionary events that happened to their hosts in the past.