Numerous sources of monitoring information have documented increases, in some cases dramatic increases, in the abundance of Double-crested Cormorants in Canada. Results from the Breeding Bird Survey (BBS) for Canada show a strong increase relative to 1970, and are moderately precise. The BBS is the only monitoring program that provides population information for the species in the Prairie Potholes Bird Conservation Region, the most important regions for cormorants. Though the trend estimate for that region has low precision, there is no doubt that the population has increased. Christmas Bird Count results for both Canada and North America also show a strong increase in the abundance of wintering cormorants, though the results for North America represent an unknown mixture of resident birds in the U.S. and Canadian migrants. Counts at colonies in Quebec (see Analysis of Seabird Colony Monitoring Program) suggest population increases of almost 4% per year, while counts in the Great Lakes rose from only 427 nests in 1979 to 58,613 nests in 2009, a 137-fold increase (Environment and Climate Change Canada and Ontario Ministry of Natural Resources, unpublished data, and see Great Lakes Decadal Colonial Waterbird Census below). Together, these varied sources of monitoring information provide strong evidence of a large increase in the abundance of this species in Canada and North America. The Double-crested Cormorant is at an acceptable level relative to its national population goal (see Canada BBS graph below).
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
Additional information on: British Columbia Coastal Waterbird Survey
Additional information on: Christmas Bird Count (CBC)
Additional information on: Great Lakes Decadal Colonial Waterbird Census
Additional information on: Seabird Colony Monitoring Program
