Habitat exploitation and interspecific competition of moulting geese in East Greenland

• Published in: Ibis
• Main Authors: MADSEN, JESPER, MORTENSEN, CHRISTIAN EBBE
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1987
• Subjects: East Greenland; Greenland; Iceland
• Online Access: http://dx.doi.org/10.1111/j.1474-919x.1987.tb03157.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1474-919X.1987.tb03157.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1474-919X.1987.tb03157.x

Jameson Land, East Greenland is a moulting area of c . 5000 non‐breeding Pink‐footed Geese and 5000 Barnacle Geese. Breeding populations of both species in the area are small and scattered. The moulting Pinkfeet originate from Iceland, and the Barnacle Geese from other parts of East Greenland. Both species arrive in the area at the end of June and moult their remiges in July. Moulting flocks of the two species seldom mix. Pinkfoot flocks are common along coastlines, in wide rivers and on lakes with open views to all sides, while Barnacle Geese predominate in smaller rivers and on lakes with surrounding hills. During moult the geese, and especially the Pinkfeet, are extremely wary and depend on a safe area of water serving as a refuge with nearby food supplies (sedge‐dominated marshes). Barnacle Geese graze in a zone 0–100 m from the refuge, Pinkfeet up to 200–250 m from the refuge. The moulting sites fill up with geese according to available marsh areas, and the grazing pressure on average amounts to 594 goose‐days per ha during the moulting period. Food intake is estimated at 149 g and 138 g organic material per 24 h by Pinkfeet and Barnacle Geese, respectively, [n 1984, which was sunny and warm, net above‐ground primary production of a Carex subspathacea marsh (the prime feeding ground during moult) from the beginning of growth to the end of July was 13–15 g dw m 2 , and it is estimated that the geese consumed 60–69% of the production. In 1983, which was cold, geese probably consumed the entire production. Goose grazing did not affect productivity, but nutrient levels were high in grazed compared with ungrazed shoots, and peaked in early July. When separate, the diet of both species comprises sedges and grasses. Where the species co‐exist the amount of mosses in the diet increases, especially in Barnacle Geese. With respect to nutrient and fibre contents, moss is a suboptimal food compared to sedges and grasses. When separate, the geese spend 41–46% of the 24 hr grazing. Where they co‐exist, Barnacle Geese ...