Evidence Supporting a Dietary Basis for Orange-Tipped Rectrices in the Cedar Waxwing (Evidencia a Favor de que el Color Anaranjado en la Punta de las Rectrices de Individuos de Bombycilla cedrorum se Debe a la Dieta)

Cedar Waxwings (Bombycilla cedrorum) normally have yellow-tipped rectrices, but juvenile waxwings with orange tail tips have been observed with increasing frequency in the eastern United States in the past 30 yr. Orange-tipped rectrices contain large amounts of the red pigment rhodoxanthin not found in normal yellow tail tips, and berries containing that pigment have been hypothesized as the source of rhodoxanthin in these feathers. At Powdermill Nature Reserve in western Pennsylvania, the first occurrence and subsequent increase in frequency of orange tail-banded juvenile waxwings correspond closely with the initial introduction and later growth and spread of two species of closely related honeysuckles (Lonicera morrowii and L. tatarica), one of which has been reported to contain rhodoxanthin. The ripe red berries of these shrubs are available from June through July. Nestling waxwings, which develop rectrices at this time, may be fed honeysuckle berries and consequently grow orange-tipped tails. Adults do not normally molt rectrices until the berries are no longer available, and nearly always have yellow-tipped tails. Several immature birds with orange tail bands were found growing yellow-tipped replacement tail feathers in September and October, after the honeysuckle fruiting period; two yellow-tipped birds were growing orange-tipped replacement feathers in July, when honeysuckle berries were available. Consumption of rhodoxanthin-containing honeysuckle berries may also account for orange variants in the Yellow-breasted Chat (Icteria virens) and Kentucky Warbler (Oporornis formosus). /// Los individuos de Bombycilla cedrorum normalmente tienen la punta de las rectrices de color amarillo, aunque en los últimos 30 años, en la parte este de los Estados Unidos, se han estado avistando con mayor frecuencia individuos juveniles con la punta de las rectrices anaranjadas. Rectrices con anaranjado contienen grandes cantidades de rodoxantina, un pigmento rojo que no se encuentra en rectrices con el amarillo típico de la especie. Se ha propuesto como hipótesis que la fuente de rodoxantina en estas plumas son bayas. En la Reserva Natural Powdermill, Pennsylvania, la primera ocasión y subsecuentemente el incremento de anaranjado en la cola de juveniles de B. cedrorum corresponde a la introducción inicial y luego el crecimiento y dispersión de dos especies de bayas (Lonicera morrowii y L. tatarica) una de las cuales ha sido informada contener rodoxantina. Las bayas ma