Variation in badge size in male house sparrows Passer domesticus: evidence for status signalling

Abstract

The relation of patterns of variation in badge size to dominance was studied in male house sparrows, Passer domesticus. Males with large badges were more dominant in winter flocks, irrespective of age, body size and body condition index. The frequency of attacks was higher with increasing similarity of badges of two contestants. Male house sparrows were more frequently engaged in attacks with males having a similar badge size when they had large badges than when they had small ones. Badge size did not change consistently with age. Breeding territory owners approached closer to, and moved less frequently in response to, a house sparrow model with a small badge than to one with a large badge. These results are consistent with a status signalling function of badge size variation in house sparrows.