The distribution of age and sex classes of wintering Snow Buntings was examined at 11 sites in North-east Scotland. These sites were all close together (relative to the distance from the breeding grounds) and therefore controlled for the widely held view that costs of migration distance can influence winter settlement patterns. They varied markedly in altitude (and consequently habitat and climate), enabling us to test the effect of site quality on settlement patterns in isolation from migration distance. The proportions of adult males and adult females increased with altitude, whilst the proportion of juvenile females decreased. Because males are the larger and more dominant sex, and adult birds have the advantage of previous experience, the distribution of age and sex classes suggests that more elevated sites are of higher quality. Consequently, we argue that environmental factors (such as reduced competition, fewer predators, or similarity to breeding conditions) are responsible for this altitudinal segregation and can therefore also help explain latitudinal segregation patterns of the age and sex classes.