Because of limited resources, biodiversity conservation practice is often reduced to measures directed at single species in the hope that this will simultaneously benefit other species in the same community. Such "umbrella species" should therefore have habitat requirements that are similar to those of the other species, whereas their spatial needs should be more extensive. The umbrella-species concept is often applied in management yet rarely tested beforehand. The Capercaillie (Tetrao urogallus) is a large forest grouse that is declining over much of its range in Central Europe. It is considered a good example of an umbrella species and is now widely receiving attention from forestry managers. We tested its usefulness as an umbrella species in the Swiss Prealps by analyzing relationships between Capercaillie occurrence and avian biodiversity and asked whether both were associated with the same habitat-structure parameters. Study plots with Capercaillie did not hold significantly higher bird diversity than plots without the grouse. However, the species richness and abundance of birds that are more or less restricted to subalpine forests (mountain birds) and that at the same time are on the red list was considerably higher in Capercaillie plots than in those without Capercaillie. Both Capercaillie and mountain birds responded positively to forest structure characterized by intermediate openness, multistoried tree layer, presence of ecotonal conditions, and abundant cover of ericaceous shrubs. Capercaillie may therefore be a useful umbrella species, at least for that part of avian biodiversity of conservation interest.