Variation in Black Bib of the Eurasian Siskin (Carduelis spinus) and Its Role as a Reliable Badge of Dominance

Abstract

Rohwer (1975, 1982) proposed that the variation and extent of color patches in the plumage of wintering birds could work as badges of social status. The major advantage of these signals would be that individuals of unequal status competing for limited resources would not need to risk accidental injury or waste energy assessing the relative fighting ability of potential opponents (Rohwer 1982). The status-signalling hypothesis has been tested in several species with variable plumage (reviewed by Whitfield 1987; see also Amat 1986, Watt 1986a, b, Fugle and Rothstein 1987, Motter 1987a, b, 1989, Jackson et al. 1988). These studies have, however, produced contradictory results. For plumage differences to act as true badges of dominance, they should correlate within and not just between sex and age classes. This has been demonstrated in only a few species (Great Tit [Parus major], J•irvi and Bakken 1984; Yellow Warbler [Dendroica petechia], Studd and Robertson 1985; House Sparrow

Prior residence effect in wintering male Eurasian siskins is not related to resource holding power

“…In this study, we found no differences between male resident and transient wintering siskins in the black bib area, which is the best proxy for RHP in male siskins (Senar et al 1993;Senar and Camerino 1998). The black bib area alone explained about half of the variation in dominance score (i.e.…”

“…Variation in the relative importance of predation and starvation risks has been proposed to explain these differences, both between and within species (Verhulst and Hogstad 1996). The black bib area of male siskins is positively associated to exploratory behaviour (Mateos-González and Senar 2012) and competitive ability (Senar et al 1993;Senar and Camerino 1998) and, hence, to the personality of birds (Réale et al 2007). Since residency is not related to the black bib size, it is probably not either related to personality, and hence, the dominance of residents over transients is not expected to result from a behavioural syndrome but from a difference in prior residency.…”

“…The black bib area alone explained about half of the variation in dominance score (i.e. RHP) among siskin males in an indoor experiment (Senar et al 1993). The other half was partially related to differences in body size and body condition, which were not either found to differ between residents and transients in this study.…”

“…Moreover, in this species, there is a plumage coloration cue, the black bib of males, that is a good proxy for RHP. The black bib size was found to be the best predictor of the dominance score in a study that analyzed the outcome of the contests between a group of male siskins, whereas age, body mass and body size did not have an effect after controlling for the black bib size (Senar et al 1993). Additionally, an experimental study showed that male siskins on the first encounter discriminate their dominance status merely by the size of the black bib (Senar and Camerino 1998).…”

Both morphological and molecular characters support speciation of South American siskins by sexual selection

“…These traits may function in a social context, as most siskin species gather in large numbers outside the breeding season, also forming mixed flocks that consist of different species. Senar and colleagues [33,34] showed in experiments that enlargements or removals of black bibs in the European siskin C. spinus, (a species resembling the ancestral C. barbata in this trait) have an effect on social status. Large bibs in spinus signalled overt aggression and thus dominant status.…”