abstract: There are considerable differences among bird species in the degree of color variation within populations. In some species, there appears to be little difference among individuals, whereas in other species, each individual seems to be unique. Why is there so much interspecific variation in within-species variability? Here I have argued that general patterns of intraspecific variation can be understood from a communication-based theoretical framework in which signalers reveal information about themselves to receivers. Birds use color to reveal seven broad kinds of information—quality, Fisherian attractiveness, behavioral strategy, genetic compatibility, kinship, individual identity, and presence. Quality signals reveal information about relative phenotypic and genetic constitution and are expected to express relatively high degrees of unimodally distributed, environmentally determined (condition-dependent) variability. In addition, quality signals can be associated with “amplifiers,” traits that increase the receiver’s perception of ornament elaboration. In contrast to quality signals, amplifiers are expected to be fixed and express low variability. Fisherian runaway selection results in traits that define attractiveness independent of quality. Fisherian traits are expected to be intense colors that demonstrate relatively low intrapopulation variability and high geographic variability (provided that different populations arrive at different equilibrium states). Strategy signals are expected when individuals form strategy-dependent cooperative alliances and include signals of gender, some forms of delayedplumage maturation, and signals of mating strategy. Strategy signals are expected to be bimodally distributed (one mode for each strategy) and can be genetically or environmentally determined, depending on the specific strategies revealed. Traits that reflect genetic compatibility for mate choice include species isolation signals and signals of genetic similarity. Species isolation processes (reinforcement and species recognition) provide the most promising scenarios to find color-based compatibility signals. Such signals are expected to be genetically fixed traits that express low variability within genetically distinct populations and high variability between them. Kinship signals facilitate discrimination of unfamiliar kin and can be stable for color-based signals, provided that signalers frequently encounter and interact with unfamiliar relatives. Such signals are expected to be based on multiple, variable, and independently assorting traits based on polymorphic loci scattered throughout the genome. Individual identity signals are “name tags” that increase overall recognizability. Signaling individual identity by color display might be widespread in birds and appears to be associated with the highest degrees of observed variability in coloration. Identity signals often display complex, multimodal distributions presumably arising from negative frequency-dependent selection acting on signal phenotypes. They are expected to express similar properties as kinship signals; however, identity signals are only used to discriminate familiar individuals (i.e., the signal must be learned by receivers). Finally, signals of presence either reveal (honest signals) or conceal (dishonest signals) an individual to receivers. Such signals should contrast (or blend) with the ambient environmental conditions and generally be fixed traits that express low degrees of unimodal variability. However, variable background conditions can easily give rise to increased phenotypic variability, particularly with cryptic coloration. These seven signal types represent non-mutually exclusive alternative communication functions for bird coloration and provide a rich arena for the provision of multiple messages by signalers. Furthermore, the framework developed here is expected to be general and should provide insight into signaling in all communication channels in all taxa.