Populations status of gulls on île Nue de Mingan

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Study Results

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Populations status of gulls on île Nue de Mingan

ROBERGE, B. 1999. État des populations de goélands de l'île Nue de Mingan et caractérisation des impacts de la faune sur la végétation . Réserve de parc national de l'Archipel-de-Mingan - 1996. Parcs Canada, Service de la conservation des ressources naturelles, Unité de gestion de Mingan. 53 p.

ABSTRACT

Damage to vegetation caused by gulls
© Parks Canada / B. Roberge / Z 02 04, 1996

The Herring Gull ( Larus argentatus ) and Muskrat ( Ondatra zibethicus ) populations on île Nue de Mingan are a potential threat to its unique vegetation. An inventory was conducted in 1996 to verify the status of the various gull populations and determine the impact of the fauna on the vegetation of Île Nue de Mingan in the Mingan Archipelago National Park Reserve. The experimental approach involved a systematic count of active gull nests coupled with an estimate of the amount of damage to vegetation caused by gulls and muskrats. The total gull population on Île Nue de Mingan was estimated at 7,124 couples in 1996, and was composed of 4,487 Herring Gull couples, 144 Great Black-backed Gull couples, 2,488 couples that were either Herring or Great Black-backed Gulls, and five Ring-billed Gull couples. Île Nue gull populations, especially Herring Gulls, have been on the decline since 1990. The exception is Great Black-backed Gulls, which are increasing in numbers. Ring-billed Gulls have all but disappeared since 1983. The gulls mainly congregate at the Eastern end of Île Nue , which is protected from prevailing winds, as well as on the elevated central plateau. Common and Arctic Stern populations (107 couples) are stable, while the Common Eider population (341 couples) is rising. These three species are, however, confined to peripheral areas avoided by gulls. The negative impact of gulls on the vegetation of Île Nue is due to trampling, physical damage and deposition of feces in nesting and roosting areas. The most frequently encountered signs of damage are patches of yellowing vegetation interspersed with areas of bare ground, although large areas of vegetation are occasionally destroyed totally. The area of vegetation damaged by gulls is currently estimated at 2,4% (54,661 m ² ) of the entire island, with approximately 0,8% (18,468 m ² ) of the island vegetation totally destroyed. Some 9,256 active and inactive muskrat burrows and feeding holes as well as five lodges have been inventoried on île Nue . Despite this, muskrats are unlikely to overpopulate the island since the wet environments and food sources preferred by these rodents are fairly rare. Muskrat burrows and holes can be found everywhere on the island but damage to vegetation caused by burrowing activities is quite low at approximately 73 m ² . Gulls use and have the most impact on the barrens, while muskrats use and have the most impact on fens and barrens. Certain fascinating and rare plants are threatened by their close proximity to gull and muskrat habitats. Passive managment measures to monitor the vegetation, gulls and muskrats on Île Nue are recommended because of the stable gull population, the limited potential for overpopulation by muskrats and the small area of vegetation that has so far been damaged by the fauna. This study emphasizes the importance of stating national management guidelines with respect to the disappearance or loss of elements of interest by natural processes in the ecosystems of Canada's national parks.

This report is available at the Regional Library of Parks Canada in Quebec (in French).