Bright coloration in birds is an important indicator of individual quality often used in social displays. Structural, carotenoid-, and melanin-based colors are long-lasting, widespread, and widely studied. Hemoglobin-based colors are ephemeral, rare, and less studied. Hemoglobin-based displays occur when an individual facultatively enhances or restricts blood flow through caruncles, combs, wattles, or other highly vascularized un-feathered skin patches. In Crested Caracaras (Caracara cheriway; hereafter “caracara”) highly vascularized ceres facultatively undergo immediately reversible hemoglobin-based color changes, hypothesized to correlate with status during contests. I predicted aggressors in contests would consistently display hemoglobin-deprived ceres (hereafter “light”), and receivers would display hemoglobin-enhanced ceres (hereafter “dark”), or vice versa. To test this hypothesis, I conducted 149 30-min group observations during which I recorded outcomes of all observed intra- and interspecific agonistic interactions involving caracaras in groups including up to 46 caracaras (x¯  =  13.4, SD  =  6.9). I recorded 2586 agonistic interactions in which I could identify cere colors and ages of both caracaras involved in an intraspecific interaction (n  =  1160), or of one caracara involved in an interspecific interaction (n  =  1426). Cere colors of caracaras were consistently light when acting as aggressors in intra- and interspecific agonistic interactions, and dark when acting as receivers. Within age classes, caracaras displaying light-colored ceres were consistently aggressors toward caracaras displaying dark ceres, and between age classes, adults with light-colored ceres were aggressors toward younger birds with dark ceres. Caracaras displaying light-colored ceres were aggressors toward Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) and caracaras with dark ceres were receivers of aggression from these species. Regardless of the cere color, caracaras were subordinate to much larger Bald Eagles (Haliaeetus leucocephalus) and dominant over much smaller American Crows (Corvus brachyrhynchos). My observations support the hypothesis that cere color is correlated with agonistic behaviors and support the signaling hypothesis by correlating specific cere colors displayed with individual roles in intra- and interspecific interactions.

En las aves, la coloración brillante es un indicador importante de calidad individual que se usa a menudo en los despliegues sociales. Los colores estructurales y basados en carotenoides y melanina han sido estudiados desde hace tiempo y de forma amplia y generalizada. Los colores basados en la hemoglobina son efímeros, raros y menos estudiados. Los despliegues basados en la hemoglobina ocurren cuando un individuo aumenta o restringe facultativamente el flujo sanguíneo a través de las carúnculas, crestas u otros parches de piel sin plumas altamente vascularizados. En Caracara cheriway, las ceras altamente vascularizadas experimentan de forma facultativa cambios de color inmediatamente reversibles basados en la hemoglobina, los cuales se piensa que están correlacionados con el estatus durante las competencias. Predije que en una competencia, los individuos agresores desplegarían consistentemente ceras carentes de hemoglobina (de aquí en más “claras”) y que los individuos que reciben la agresión desplegarían ceras realzadas por la hemoglobina (de aquí en más “oscuras”) o viceversa. Para evaluar esta hipótesis, realicé 149 observaciones grupales de 20 minutos cada una durante las cuales registré los resultados de todas las interacciones agonísticas intra e inter-específicas observadas que involucraban a ejemplares de C. cheriway en grupos de hasta 46 individuos (x¯  =  13.4, DE  =  6.9). Registré 2586 interacciones agonísticas en las cuales pude identificar el color de l