The Effect of Oil Spraying on Eggs of Double-Crested Cormorants

Spraying eggs with oil has been used as a method of decreasing the reproductive success of super abundant avian species. Double-crested Cormorant (Phalacrocorax auritus) abundances have created a potential disturbance to some endangered species of birds, sport fishing communities and aquaculture facilities. The hatching success of oil sprayed Double-crested Cormorant eggs was investigated. Oil spraying was done during the first, second, or third week of the eggs incubation to determine the most effective time during the incubation period for a one-time treatment. The oil spraying technique was 95–98% effective at preventing hatching. Hatching success was independent of the week of incubation that an egg was sprayed with oil. The maximum number of eggs on the colony occurred four weeks after the first egg was laid. This would be the most efficient week to spray the colony to decrease hatching success.