In response to human activity and ecosystem changes, large gulls in eastern North America have shown a variety of population trends over the last 100 years. Seven years of capture-mark-recapture data were analyzed for Herring (Larus argentatus) and Great Black-backed (L. marinus) gulls breeding in eastern Newfoundland, Canada to estimate apparent survival and survival rates. Estimated survival was 0.864 for Great Black-backed Gulls and 0.837 for Herring Gulls. For both species, the survival rate calculated using live and dead encounters was higher than the apparent survival rate calculated from resighting data only and added almost an additional year of expected life. While these values are in the range of survival rates reported from other studies along the eastern coast of North America, the values for Herring Gulls were lower than survival rates reported elsewhere in North America and Europe. The lower survival rates seen in eastern North American Herring Gulls may be attributable to characteristics of the migration and wintering habitat, including poorer habitat quality (i.e., highly developed and industrialized east coast) and possibly gull (Laridae) control programs.
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