PATTERN OF RECOVERIES OF BANDED RAZORBILLS (ALCA-TORDA) IN THE WESTERN ATLANTIC AND SURVIVAL RATES OF ADULTS AND IMMATURES

In North America, Razorbills (Alca torda) breed in colonies scattered along the coast of Atlantic Canada and the northeastern coast of Maine , but with primary concentrations in Labrador and the Gulf of St. Lawr ence. Given the small North American population (ca. 20,000 pairs) and the large decrease which occurred in the Gulf of St. Lawrence during the 1970s, an intensive effort to band Razorbills on the North Shore o f the gulf and to a less extent in Labrador was accomplished between 1 981 and 1995. Using banding recoveries of Razorbills from this operati on, and former one on the Atlantic coast, we traced their movements an d showed how the species could be exposed to different risks during th e non-breeding season. More than 50% of the recoveries came from the l egal Thick-billed Murre (Uria lomvia) hunt in Newfoundland, suggesting that shooting could be the most important mortality factor for immatu re birds. A study of color-banded birds combined with triangular bands that could be read from a distance was started in 1990 at St. Mary's Islands (Quebec) and suggests a mean annual adult survival rare of 90% . This measure of adult survival combined with productivity figures an d current population trends allowed to estimate a 38% survival rate fo r immatures.