ARCTIC FOX INFLUENCE ON A SEABIRD COMMUNITY IN LABRADOR - A NATURAL EXPERIMENT

The Gannet Islands contain the single most important seabird colony in Labrador, both in terms of numbers and species diversity. In 1992, we discovered arctic foxes (Alopex lagopus) on these islands during the breeding season. Of five islands examined, two had resident foxes (in one case breeding), two had been visited by foxes earlier in the seaso n, and one had no foxes and had not been visited. A comparison of thes e islands in 1992 and with our detailed studies from the early 1980s, revealed the effect that foxes had had on seabirds. On islands with fo xes, Razorbills (Alca torda), Common Murres (Uria aalge), and Thick-bi lled Murres ((U. lomvia) had ceased breeding. Atlantic Puffins (Frater cula arctica) continued to attempt to breed, but fox predation on adul t birds and eggs was intense and breeding success low. On islands visi ted by foxes earlier in the season, the number of breeding Razorbills was reduced, and breeding by Common Murres was delayed by 2-3 weeks.