A re-assessment of the significance of status signalling in populations of wild great tits, Parus major

Abstract

The great tit is quoted as a species exhibiting badge signalling of social status, through its black ventral stripe. Two empirical studies on which such statements are based, however, are flawed (Järvi & Bakken, 1984, Anim. Behav., 32, 590–596; Järvi et al., 1987, Ethology, 76, 334–342) and there is little evidence bearing on whether or not ventral stripe size is a costly trait. A third study provides evidence of status signalling by wild great tits but took place outwith the birds' territorial system (Maynard Smith & Harper, 1988, Phil. Trans. R. Soc. Ser. B., 319, 557–570) . The present study examined relationships between dominance and stripe size within areas subsequently used for breeding. There was a weak positive correlation between stripe size and dominance in female dyads, but not in males. Female dyads interacting at feeders involved birds more similar in stripe size than did random samples of dyads drawn from the winter population. Interactions between females were more likely to escalate to attacks the more similar were the stripe sizes of the opponents. Neither relationship was found for male dyads. Status signalling may have been of limited significance amongst female great tits, but was not involved in resolving male contests. The importance of territory establishment for male great tits may be one long-term factor making the value of winning interactions with other males too great for badge signalling to be used, except where birds are interacting outwith their territorial system. The possible importance of positive feedback between social status, physiological state and plumage is discussed, and it is emphasized that, in species with only one annual moult, selection pressures exerted during the breeding season may also be important in the evolution of plumage characteristics.