Variation in nutritive quality over time and among forage plants is important for herbivores such as geese. We examined the seasonal variation of some nutritive attributes (nitrogen, neutral detergent fibre, and phenolic compounds) of five plant species consumed by Greater Snow Geese ( Chen caerulescens atlantica ) L. in mesic tundra, a habitat where goose feeding ecology has been little studied compared with wetlands. We sampled ungrazed, aboveground plant tissues five times at 10–14 d intervals between 1 July and 15 August 2003 on Bylot Island, Nunavut. The species were Arctagrostis latifolia (R. Br.) Griseb. (Gramineae), Luzula nivalis (Laest.) Beurl. (Juncaceae), Oxytropis maydelliana Trautv. (Leguminosae), Oxyria digyna (L.) Hill, and Polygonum viviparum L. (both Polygonaceae). All species showed a seasonal decline in nitrogen content in both leaves and flowering heads (includes flowers and fruits) but the amplitude was variable among species (from 10% to 62% decline depending on the species). Neutral detergent fibre concentration in leaves remained stable or increased slightly over time in contrast to flowering heads where it increased in all species (from 7% to 94%). Fibre content was higher in flowering heads than in leaves. The total content of phenolic compounds varied throughout the summer. In some cases, the content of phenolic compounds remained stable but in others it initially increased and then decreased later on, or it increased throughout the summer. Seasonal variations in plant nutritive quality were smaller than interspecific differences. The nitrogen content of forbs (especially Oxytropis ) was high and their fibre content low compared with the grass and rush species (Luzula), particularly during the early summer.
