Feeding and Chick-Rearing Areas of Common Loons

Abstract

We characterized the feeding and chick-rearing areas used by 16 resident pairs of common loons (Gavia immer) on 3 large lakes in Maine. Adults preferred water depths of 1.1-2.0 m and avoided depths >3 m for feeding in most breeding territories. Chicks were kept in shallow water areas ( 3 m) distant from shore were avoided by chicks and adults. We suggest that near-shore recreation may be more detrimental to loons than man's activities in deep, open water. J. WILDL. MANAGE. 53(1):72-76 The breeding range and population size of the common loon have been reduced in the lower 48 United States (McIntyre 1986) and parts of southern Canada (McNicholl 1988). Development of shoreline areas and aquatic recreational activities by humans have affected the availability and suitability of summer habitat and are believed to be the primary causes of the decline (McIntyre 1986). Population recovery efforts have focused on public education and protection of nest sites in most areas (Sutcliffe 1979, Wood 1979). Nesting areas of common loons are described (Vermeer 1973, McIntyre 1975, Sutcliffe 1980) and strategies for protection have been suggested (Strong et al. 1987). Chick-rearing and feeding areas are important components of the summer habitat of common loons. Some features of chick-rearing habitat have been described by McIntyre (1983). Strong et al. (1987) reported annual use of nursery areas but a description of chick-rearing habitat is incomplete and feeding habitat has not been studied. Our objectives were to characterize chick-rearing and feeding areas of common loons on large lakes. We thank R. C. Burke II, F. J. Dibello, D. B. Kingman, Jr., P. G. R. Jodice, R. Souza, and C. P. Terry for their help in data collection. W. A. Halteman provided statistical assistance. J. A. Sherburne initiated the project that was funded by the Maine Department of Inland Fisheries and Wildlife (MDIFW). The Maine Cooperative Fish and Wildlife Research Unit, University of Maine Wildlife Department, Libby's Sport Camps, R. S. Skinner, and F. Voight provided support services. This is contribution 1280, University of Maine Agricultural Experiment Station. STUDY AREAS AND METHODS We conducted field work from May through August 1982-84 on Grand Lake Seboeis (1,006 ha), Snowshoe Lake (258 ha), and Millinocket Lake (1,094 ha) in northern Maine. Lake shapes were irregular with numerous coves, peninsulas, and islands. Maximum water depths were 10, 13, and 16 m, respectively. At least 20 species of game and forage fish typical of northern Maine occurred in the lakes (MDIFW, unpubl. data). Human use of lakeshores was limited; the few cabins were used only sporadically during summer. Little recreational use occurred. We collected activity and location data on all resident pairs from May through August. Individuals were unmarked, thus we were unable to identify individual birds; however, resident pairs generally occupied specific areas on the lakes. We delineated territories for each resident pair based on observations during the 3year period. Pairs did not occupy mutually exclusive areas (Strong and Bissonette 1988) so territory boundaries were approximated using observations of territorial behavior and social