Impacts of Intraspecific Kleptoparasitism and Diet Shifts on Razorbill Alca torda productivity at the Gannet Islands, Labrador

• Main Authors: Lavers, JL, Jones, IL
• Format: Article in Journal/Newspaper
• Language: English
• Published: African Seabird Group 2007
• Subjects: Biological Sciences; Ecology; Ecology not elsewhere classified; Gannet Islands; Alca torda; Razorbill
• Online Access: http://www.marineornithology.org/; http://ecite.utas.edu.au/77910

Intraspecific kleptoparasitism, the stealing of food from members of the same species, has received widespread but mostly superficialattention in the scientific literature. However, the effects of such behavior can be significant. Here we report on high rates of intraspecifickleptoparasitism in the Razorbill Alca torda at the Gannet Islands, a behavior that appears to be colony-specific. Razorbills carry their preyconspicuously in the bill, making them vulnerable to kleptoparasitic attacks from neighboring birds. We examined the relationship betweenthe frequency of kleptoparasitic attacks and the prey species carried by breeding adults. During 20032006, 69% of all Razorbills carryingfood to a chick were attacked (n = 182) and of these attacks, 18% (n = 22) were successful. Group attacks (two or more kleptoparasites) weremore successful numerically (27%, n = 71), but only one member of the group ever received the reward. The frequency of kleptoparasitismobserved by Razorbills at the Gannet Islands is one of the highest reported for any seabird, including many specialist kleptoparasites such asfrigatebirds. This finding, combined with the lowest observed Razorbill productivity (overall success = 0.39, n = 222) for the Gannet Islandsand drastic shifts in diet, may indicate decreased food availability.