Hamilton and Brown suggested that bright autumn coloration in trees is an energetically expensive and therefore honest (handicap) signal of defensive commitment against insects. If this is so, one should expect that the intensity of the proposed signal should depend strongly on tree health. However, to the best of our knowledge, the link between vigour and autumn colour has never been tested. We explored the relationship between autumn coloration and tree condition (i.e. leaf fluctuating asymmetry) in mountain birch (Betula pubescens). Our results indicate that bright autumn birches are in better condition and therefore consequently should be better at combating herbivores.