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Thayer's Gulls breed in restricted areas across the Canadian Arctic, and are not targeted by any large-scale, systematic monitoring programs. The species is common along the Pacific coast in winter, and is documented by both the Christmas Bird Count (CBC) and the British Columbia Coastal Waterbird Survey (BCCWS). However, results from the two surveys are contradictory; CBC indicates a large increase since 1970, while the BCCWS indicates a decrease since 1999. These surveys may be unreliable for Thayer’s Gull because the numbers sighted could be influenced by an increasing tendency for birds to use developed coastal habitats such as lawns and garbage dumps. Repeated observations from known breeding areas are few. However, colony counts up to 2009 suggest no substantial changes in the abundance of Thayer's Gulls in the southwestern Foxe Basin (Gaston, A. J., M. L. Mallory and H. G. Gilchrist, Environment Canada, unpublished report) and this area may support one third of the global population. These varied results and the absence of strong data from large parts of the breeding grounds means data are insufficient to determine its status.
Additional information on: Thayer's Gull Colony Counts
View numerical data of the graph.
Additional information on: British Columbia Coastal Waterbird Survey
Assessment date: 2011
Additional information on: Christmas Bird Count (CBC)
