Distribution and Abundance of Waterbirds in Summer in Severn Sound (Georgian Bay), Lake Huron: an IJC Area of Concern

Abstract

The shoreline of Severn Sound was surveyed for waterbirds from late May to July in 1991 and 1992. The Sound was divided into 32 subareas and traversed by powerboat, paralleling the shoreline, 100 to 150 m offshore. More than 10,000 birds of 14 species were identified during the study. Herring and ring-billed gulls were the most numerous species recorded (66% of total) followed by Caspian terns (14%), common terns (5%), Canada geese (5%), and black terns (4%). The number of waterbird species varied significantly among sub-areas, ranging from 2 to 13, and was greatest in Hog Bay and Matchedash Bay. The number of waterbirds also varied significantly among sub-areas, ranging from 1.6 to 46.2 per km, and was greatest in Penetanguishene Bay, Midland Bay, Matchedash Bay, and Hog Bay. Relatively undeveloped areas with emergent vegetation and cattail marshes in Hog, Matchedash, and Sturgeon bays were major feeding and loafing areas for species less common and more “sensitive” to human presence such as Caspian and black terns and common moorhens. Areas along the northern shoreline associated with Roberts and Quarry islands were focal points for species such as ospreys, double-crested cormorants, and common terns. The more urban and heavily developed shoreline near the towns of Midland and Penetanguishene was heavily used by species, such as gulls, Canada geese, and mallards, which appear to be more tolerant of human activity. The conservation and protection of these natural habitat areas that are heavily used by waterbirds is an important consideration in any further shoreline development, particularly in the southern portion of the Sound.