Ornamental plumage does not signal male quality in red-billed queleas

Abstract

Sexually selected ornaments often function as condition-dependent signals of quality (or`indicators'). When ornamentation is costly, only high-quality individuals can a¡ord to produce the most elaborate signals. The plumage ornamentation of male red-billed queleas, Quelea quelea, is an ideal candidate for an indicator because it is continuously variable, conspicuous, sexually dimorphic, is displayed only during breeding and is partially based on carotenoid pigmentation. However, I show here that quelea plumage is not an indicator because ¢rst, plumage colour is not correlated with physical condition or age; second, plumage colour is a genetically determined phenotype that is unresponsive to environmental variation; third, di¡erent plumage characters have bimodal distributions; fourth, plumage characters vary independently of one another; and ¢nally, plumage colour is not correlated with reproductive success. To my knowledge, this is the ¢rst demonstration of non-condition dependence in colourful and sexually dimorphic breeding ornamentation. Instead, plumage variation may function as a sexually selected signal of individual identity among territorial males that nest in huge, densely packed and highly synchronized colonies.

Candidate genes for carotenoid coloration in vertebrates and their expression profiles in the carotenoid-containing plumage and bill of a wild bird

“…Throughout their non-breeding season, queleas are sexually monomorphic, with a melaninbased dull brown plumage, and a carotenoid-based red bill, eye-rings and legs [8 -10]. The red coloration in bills and feathers is due to the presence of enzymatically derived keto-carotenoids similar to those found in several other bird species, such as the zebra finch ( [8,9], table 1). Prior to the breeding season, female queleas lose the carotenoid coloration of their bare body parts.…”

“…The mask coloration is due to differential levels of eumelanin deposition and also has a strong genetic basis. The mask and breast polymorphisms assort independently of each other [8,9] and both traits are developmentally fixed, genetically determined characters of which the expression appears to be independent of phenotypic condition or environmental variation [8,9]. The polymorphic breeding plumage is hypothesized to be under sexual selection for signalling individual identity among neighbouring territorial males and the high levels of variability present are probably maintained through negative frequency-dependent selection [11,12].…”

“…Breeding males, however, retain this coloration and also moult into a bright nuptial plumage that is polymorphic for both breast colour that varies from red to buff and for face colour that varies from white to black (figure 1). The breast colour polymorphism is due to differences in carotenoid deposition and is inherited in a quasi-Mendelian fashion [8,9]. In buff-breasted males, carotenoids are absent, the buff coloration being owing to phaeomelanin, whereas red-breasted males have variable amounts of keto-carotenoids present.…”

How plant?animal interactions signal new insights in communication

“…Although some male ornaments function as accurate indicators of male quality [35,36], the general occurrence of such 'honest' signals remains controversial [37,38]. Conflicting reproductive strategies between, and behavioural flexibility within, the sexes [4] might constrain the evolution of honest sexual signals.…”

A permanent signal related to male pairing success and survival in the lizard Psammodromus algirus

“…The slides were digitized by means of Nikon Coolscan III and Adobe Photoshop (Dale, 2000) was used to quantify colour saturation in six randomly selected points of the anterior patch of the left side. We selected the anterior blue patch because is usually larger than the others.…”