Do Melanin- or Carotenoid-Pigmented Plumage Ornaments Signal Condition and Predict Pairing Success in the Kentucky Warbler?

Yellow and red feathers pigmented by carotenoids can signal a bird's condition and are important to both female choice and male-male competition. Melanin-based ornaments are thought to be less effective than carotenoid ornaments as indicators of condition, though their signal function is still relatively unstudied. We examined both carotenoid and melanin-pigmented feather ornaments in a single species, the Kentucky Warbler (Oporornis formosus). Both males and females of this species have melanin-pigmented ornamentation (black crown, black face) and carotenoid-pigmented ornamentation (lemon-yellow undersides). Melanin-pigmented plumage patches were larger in males than females, and males had brighter breast plumage, with a larger ultraviolet component, than females. Among males in the wild, individuals in better condition had more extensive black caps and faces, but not brighter-yellow breasts. Males with larger black caps were more likely to attract mates. This work demonstrates that, in a species with both melanin- and carotenoid-pigmented plumage, melanin-pigmented ornaments can signal condition, and that a melanin-based signal can explain variance in mating success. ¿Funcionan Como Indicadores de la Condición Física y Predicen del Éxito de Apareamiento los Ornamentos del Plumaje Pigmentados con Melanina o Carotenoides en Oporornis formosus? Resumen. Las plumas amarillas y rojas pigmentadas por carotenoides pueden indicar la condición de un ave y son importantes tanto para la elección de machos por parte de las hembras como para la competencia entre machos. Se cree que los ornamentos a base de melanina son menos efectivos como indicadores de condición que los ornamentos carotenoides, aunque su función como señal ha sido menos estudiada. Examinamos plumas ornamentales pigmentadas con carotenoides y melanina en la especie Oporornis formosus. Tanto el macho como la hembra presentan ornamentación pigmentada con melanina (corona negra, rostro negro) y ornamentación pigmentada con carotenoides (flancos inferiores amarillo-limón). Los parches de plumaje pigmentados con melanina fueron mayores en los machos que en las hembras y el plumaje del pecho de los machos fue más brillante y con un componente ultravioleta mayor que el de las hembras. Entre los machos en ambiente natural, los individuos con mejor condición tuvieron coronas y rostros negros más extensos, pero no tuvieron pechos amarillos más brillantes. Los machos con coronas negras más extensas tuvieron una mayor probabilidad de atraer parejas. Este trabajo demuestra que en una especie con plumaje pigmentado con melanina y carotenoides, los ornamentos pigmentados con melanina pueden señalar la condición de los individuos, y que una señal con base en melanina puede explicar la varianza en el éxito reproductivo.

Ranging of Conspecific Songs By Kentucky Warblers and Its Implications for Interactions of Territorial Males

Kentucky warblers (Oporornis formosus) each sing a single song pattern. To determine whether males could range (estimate the distance to) conspecific songs, we presented clean and reverberated versions of strangers' songs to 12 males in a factorial design. To assess differences between the playbacks and the subjects' own songs or neighbors' songs, we measured differences in minimal repetition periods between repeated acoustic elements in songs, features that could contribute to assessment of reverberation. Results indicated that Kentucky warblers can range conspecific songs and that similarity between playback songs and established neighbors' songs or a subject's own songs did not enhance this ability. Direct evidence that males misjudged the distance to reverberated playbacks excluded other interpretations of the results based on differences in the detectability or habituation of clean and reverberated songs. These results suggest further that assessment of reverberation is sufficient for ranging and that perceptual analysis of song is not necessarily linked to overt production. As a consequence, repertoires of songs do not necessarily promote interference between territorial neighbors.

Avian attendance and foraging at army-ant swarms in the tropical rain forest of Los Tuxtlas, Veracruz, Mexico

ABSTRACTForaging and attendance of birds at army-ant swarm raids were studied in the tropical rain forest of Los Tuxtlas, Mexico. Sixty-eight raiding swarms were intercepted over a four-year period of which 57% were Eciton burchelli and 43% Labidus praedator. A total of 461 birds (37 species/12 families) were recorded at swarms of E. burchelli and 208 birds (34 species/10 families) were recorded at L. praedator swarms. The mean number of bird species detected per swarm was 7.2 at E. burchelli raids and 5.6 at L. praedator raids. Red-throated ant-tanagers (Habia fuscicauda) were most frequently seen at the swarms of both army-ant species. Other important species were the golden-crowned warbler (Basileuterus culicivorus), the white-breasted wood wren (Henicorhina leucosticta) and the Kentucky warbler (Oporornis formosus). Swarms of both army-ant species were active year-round. Birds weighing between 20 and 40 g dominated perches closest to the ground and the central zone of the swarms, richest in animal prey. Birds weighing less than 20 g occupied higher perches and tended to forage in more peripheral zones. At Los Tuxtlas raiding swarms of army ants are important in the foraging ecology of 44 bird species, including 12 North American migrants.