Behavior of Alcids with Tail-Mounted Radio Transmitters

-We compared the length and number of absences from the colony/day and the prey delivered to the young of Common Murres (Uria aalge) and Razorbills (Alca torda) which carried radio transmitters, and controls of these species without transmitters. The transmitters were mounted on the upper side of the tail. Birds with transmitters tended to make fewer trips/day, make fewer short trips and return more often without a fish for their chick than controls. These results indicate possible adverse impacts of transmitters on the energetics and foraging behavior of alcids. The various merits of tail and back-mounted transmitters for alcids are discussed. Received 2 February 1989, accepted 4 April 1989.