University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Symposium on Double-Crested Cormorants: Population Status and Management Issues in USDA National Wildlife Research Center the Midwest Symposia December 1997 Review of the Population Status and Management of Double- Crested Cormorants in Ontario C. Korfanty W.G. Miyasaki J.L. Harcus Follow this and additional works at: https://digitalcommons.unl.edu/nwrccormorants Part of the Ornithology Commons Korfanty, C. ; Miyasaki, W.G.; and Harcus, J.L., "Review of the Population Status and Management of Double-Crested Cormorants in Ontario" (1997). Symposium on Double-Crested Cormorants: Population Status and Management Issues in the Midwest. 14. https://digitalcommons.unl.edu/nwrccormorants/14 This Article is brought to you for free and open access by the USDA National Wildlife Research Center Symposia at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Symposium on Double- Crested Cormorants: Population Status and Management Issues in the Midwest by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Symposium on Double-Crested Cormorants 130 Population Status and Management of Double-Crested Cormorants in Ontario Review of the Population Status and Management of Double-Crested Cormorants in Ontario By C. Korfanty, W. G. Miyasaki, and J. L. Harcus Abstract: We prepared this review of the status and pairs on the Canadian Great Lakes in 1997, with increasing management of double-crested cormorants (Phalacrocorax numbers found on inland water bodies. Double-crested auritus) in Ontario, with management options, in response to cormorants are protected in Ontario, and there are no concerns expressed about possible negative impacts of large population control programs. With increasing numbers of the numbers of the birds on fish stocks, and vulnerable, threat- birds, population management options were considered, ened and endangered species. Double-crested cormorants ranging from no controls, to controls in specific local areas, to are native to Ontario and were first recorded breeding on widespread controls. The latter does not appear to be Lake of the Woods in northwestern Ontario in the late 1700’s. justified because evidence suggests that cormorants have The birds spread eastward to colonize all of the Great Lakes not had significant effects on sport, commercial or small by the 1930’s. A decline in cormorant populations on the forage fish on an ecosystem basis. Control measures in Great Lakes from the 1950’s to the 1970’s has been attrib- specific local areas may be justified for certain management uted mainly to chemical contaminants and resulting lower purposes, such as protection of endangered species. reproductive success. Populations on the Great Lakes have increased dramatically since the 1970’s in response to Keywords: double-crested cormorant, population control, reduced contaminant levels and increased abundance of management options, Ontario small forage fish. There were an estimated 36,000 breeding The abundance of double-crested cormorants 1997. The draft report was distributed to other govern- (DCCO’s) in Ontario has increased dramatically over ment agencies, interest groups, and other interested the last 2 decades. This situation has prompted parties who had contacted MNR regarding DCCO’s. intense public discussion and many inquiries about the The draft report was also posted, as a registry pro- impact of this increase. For example, Ontario sport posal file, for a 30-day public comment period, on the and commercial fishermen have expressed concerns Electronic Registry in accordance with the require- that increasing DCCO numbers are having adverse ments under the Ontario Environmental Bill of Rights. effects on fish stocks and that steps should be taken to The objectives of the consultation process were to control cormorant populations. Other interest groups ensure as complete an information base as possible, and interested parties, including naturalist groups, to ensure accurate interpretation of existing informa- maintain that DCCO’s are not having significant tion, and to determine reviewer thoughts on manage- impacts on fish stocks, are part of the natural ment options. The comments received were consid- ecosystem, and do not warrant the implementation of ered and used to produce a revised report at the end control measures. However, there are some concerns of 1997 (Korfanty et al. 1997). about the potential destruction of wildlife habitat— The purpose of this paper is to summarize the especially that of vulnerable, threatened and history and updated population status of DCCO’s in endangered species—caused by nesting DCCO’s. Ontario prior to developing and recommending a In response to these concerns, we reviewed the management approach for the Province. Any recom- population status of, and the environmental impacts mended management approach will need to be consis- caused by, DCCO’s in Ontario. A draft report was tent with the following MNR goals: (1) to secure prepared summarizing the history and current status of healthy ecosystems in terms of healthy populations DCCO’s in Ontario, based on an overview of the and communities, integrity of natural processes, and scientific literature, discussions with cormorant experts, biological diversity; (2) to identify and protect provin- a survey of Ministry of Natural Resources (MNR) field cially significant natural heritage features and land- staff, and a national survey of other Provincial natural scapes; and (3) to provide a variety of opportunities for resource management offices. The draft report also enjoyment, appreciation, and use of fish and wildlife, presented a series of management options. Public including opportunities for viewing and fishing. consultation on the draft report began on February 23, 131 Symposium on Double-Crested Cormorants Environmental Bill of Rights DCCO’s were nesting in the North Channel of Lake Huron by 1931 and established breeding colonies on The MNR’s interest in environmental protection and Lake Ontario by 1938 and on Lakes Erie and St. Clair ecological integrity is further expressed through its by 1939 (Cadman et al. 1987, del Hoyo et al. 1992, “Statement of Environmental Values” (SEV), prepared Weseloh and Collier 1995). under the Ontario Environmental Bill of Rights. The DCCO’s are now commonly found inland around SEV not only records MNR’s commitment to the bodies of fresh water, along the shores of large lakes environment but also indicates how MNR will be and, less frequently, around smaller inland lakes. The accountable for ensuring consideration of the environ- Great Lakes population migrates south along the ment in its decisions. Mississippi River or travels east to the Atlantic coast and then south to the gulf coast (Cadman et al. 1987, del Hoyo et al. 1992, Weseloh and Collier 1995). History DCCO’s feed primarily on small, shallow-water fish. Prey species vary locally and regionally and in The DCCO is a conspicuous, black, diurnal bird that is Ontario include alewife (Alosa pseudoharengus), native to Canada. Cormorants are very sociable birds rainbow smelt (Osmerus mordax,) yellow perch (Perca and nest in colonies on undisturbed islands with a flavescens), and, to a lesser extent, white suckers convenient food supply nearby. They build their nests (Catostomus commersoni), pumpkinseed (Lepomis in trees near water or on the ground (i.e., on rocks, gibossus), sculpins (Cottus spp.), crappie (Pomoxys islets, cliff tops, and ledges) on the same islands in spp.), bass (Micropterus spp.), and sticklebacks successive years. In establishing a new colony, (Gasterosteidae) (Weseloh and Collier 1995, Neuman DCCO’s often occupy an island for a few years before et al. 1997). nesting. Egg-laying begins in late April and early May DCCO’s expanded their breeding range and following courtship and nest-building activities. Eggs colonized the Great Lakes between the 1900’s and hatch in about 25 to 29 days, and the chicks are 1950’s. By the fifties, the DCCO population on the fledged in about 42 days and reach independence in Canadian Great Lakes peaked at about 900 nests (i.e., about 70 days (Cadman et al. 1987, del Hoyo et al. about 1,800 adults plus juveniles and nonbreeding 1992, Weseloh and Collier 1995). birds). By 1946, sport and commercial fishermen DCCO’s breed throughout Canada from the claimed that DCCO’s were feeding on large quantities Pacific coast, through the Canadian prairies and the of desirable commercial and sport fish, and they called Great Lakes, and along the St. Lawrence River to the for a DCCO control program. In response to these Maritime Provinces and Newfoundland. Breeding pairs concerns, a DCCO control program was introduced in have not been recorded in the Yukon, but there is Ontario, primarily on Georgian Bay (Cadman et al. evidence of breeding in the Northwest Territories 1987, Weseloh and Collier 1995). islands in James Bay off the Quebec coast (Strutton Early control measures included the destruction Island, Caroline Shoals, Eastmaine and Wayrock) of eggs, but the birds responded by laying more eggs (D. McRae, pers. commun.). In Ontario, DCCO’s have at new sites. Later methods of control included been breeding on Lake of the Woods at least since spraying eggs with a solution of formaldehyde and 1798. The species moved eastward into Lakes soap, which suffocated the developing embryo but left Superior and Nipigon between 1900 and 1920, with the the eggs intact. Hatching failure could also have been first nesting in the Great Lakes occurring on the far due to the direct toxic effects of the formaldehyde western end of Lake Superior in 1913 (Smith 1957). solution. DCCO pairs continued to incubate sprayed 132 Population Status and Management of Double-Crested Cormorants in Ontario but intact clutches for the full incubation period until it sites, for a total increase of 270 percent (an average of was too late in the season to start a new clutch (Chris- 39 percent annually) between 1981 and 1985. By tens and Blokpoel 1991, Weseloh and Collier 1995).