Breeding populations of Double-crested (Phalacrocorax auritus) and Pe- lagic Cormorants (P. pelagicus) were surveyed in the Strait of Georgia, British Colum- bia, in 1983. Double-crested Cormorant numbers have increased 2.4-fold and Pelagic Cormorant numbers 1.1-fold since 1975. Double-crested Cormorant populations are presently not only increasing in British Columbia but all across Canada and in the northeastern United States. These increases are thought to be the result of decreased disturbance and persecution by man. Drent and Guiguet (1961) provided the first overview of the status of nesting seabirds in British Columbia. Those authors reported population increases for surface-nesting seabirds for which information was available, including the Double-crested Cormorant (Phalacrocorax auritus) and Pelagic Cormorant (P. pelagicus). Drent and Guiguet (1961) suggested that cormorant increases resulted from climatic amelioration and the cessation of egg collecting by man. Campbell (1976) conducted an extensive survey of nesting seabirds in southern British Columbia in 1974 and 1975 and found that cormorant pop- ulations had increased considerably since Drent and Guiguet's survey. In 1983, we conducted a survey of the breeding populations of Double-crested and Pelagic Cormorants in the Strait of Georgia and southeastern Vancouver Island to con- tinue the assessment of population trends of cormorants. The second objective was to compare population trends of Double-crested Cormorants in British Columbia with those elsewhere in North America.
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Vermeer et al. (1984) studied this question.