Physiological Correlates of Urbanization in a Desert Songbird

Rapid worldwide urbanization is creating novel environments to which animals must adapt, a topic of growing interest for biologists. Studies of how organisms are affected by cities historically centered on large-scale censusing of populations, but recent investigations have considered finer-scaled, urban-rural differences among individuals and species in their behavior, morphology, and physiology, specifically as they relate to urban stress. A number of factors (e.g., corticosterone (CORT)-related stress response) may contribute to the degree of stress experienced by animals living under urban versus natural conditions, but several physiological variables have yet to be considered together in a large-scale assessment. Here, in a widespread species of desert passerine (the house finch, Haemorhous mexicanus), we quantified variation in plasma oxidative stress, plasma concentrations of vitamins and carotenoids, and body-mass of males in three successive seasons (winter, spring, and late summer/early fall) along an urban-rural gradient in Phoenix, Arizona, USA. We found that degree of urbanization was: (1) negatively related to circulating vitamin A concentrations in winter, (2) positively correlated with body-mass during spring, and (3) negatively associated with plasma concentrations of two carotenoids: zeaxanthin (during breeding) and 3-hydroxy-echinenone (3HE) (during molting). The striking link between 3HE levels and urbanization is consistent with previous research showing that urban songbirds have lower carotenoid levels and faded plumage; our finding is the first to implicate specific effects on a metabolically derived carotenoid for coloration. The fact that we observed only season-specific links between urbanization and indicators of quality in finches suggests that (at least for these metrics) there are no strong, lasting urban pressures imposed on finch physiology over the year. Interestingly, we found that a metric of plasma oxidative stress (lipid peroxidation) was positively correlated with levels of two carotenoids (lutein during breeding and 3HE during molting), which is consistent with a prior study of ours showing that finches with redder plumage deposit higher levels of CORT in their feathers; taken together, our studies suggest complex associations between carotenoids and stres

The effects of sun exposure on carotenoid accumulation and oxidative stress in the retina of the House Finch (Haemorhous mexicanus)

Additional file 1: Tables S1–8. Detailed data tables from each of the experimental comparisons

Astaxanthin is responsible for the pink plumage flush of Franklins and Ring-billed gulls

ABSTRACT. Carotenoid pigments produce the red, orange, and yellow plumage of many birds. Carotenoidcontaining feathers are typically rich in color and displayed by all adult members of the species. In many gulls and terns, however, an unusual light pink coloring (or flush) to the normally white plumage can be found in highly variable proportions within and across populations. The carotenoid basis of plumage flush was determined in an Elegant Tern (Sterna elegans; Hudon and Brush 1990), but it is not clear if all larids use this same mechanism for pink plumage coloration. We examined the carotenoid content of pink feathers in Franklin's (Larus pipixcan) and Ring-billed (Larus delawarensis) gulls and found that a single carotenoid-astaxanthin-was present. Astaxanthin was primarily responsible for the flush in Elegant Terns as well, but was accompanied by other carotenoids (e.g., canthaxanthin and zeaxanthin), as is typical of most astaxanthin-containing bird feathers. In both gull and tern species, carotenoids were contained within feathers and did not occur on the plumage surface in preen oil, as some have previously speculated. We hypothesize that some gulls turn pink because they acquire unusually high amounts of astaxanthin in their diets at the time of feather growth. It is tempting to link the increase in sightings of pink Ringbilled Gulls since the late 1990s with the introduction of pure, synthetic astaxanthin to the diets of hatchery-raised salmon. SINOPSIS. Astaxantina, responsible del plumaje Rosado en Larus pixpican y Larus delawarensis Los pigmentos carotenoides son los responsables de la coloración roja, anaranjada y amarilla en el plumaje de aves. Plumas que contienen carotenoides, generalmente son ricas en color y son mostradas en variados patrones de conducta por los adultos con dicha coloración. No obstante, en muchas gaviotas se puede observar una coloración rosada, en vez del típico plumaje blanco y su proporción puede ser variable en una o entre poblaciones. La presencia de carotenoides, y plumaje rosado, fue documentado en Sterna elegans, pero no quedo claro, si el mismo tipo de mecanismo aplica a otros laridos. Examinamos el contenido carotenoides en plumas rosadas de las gaviotas, Larus pixpican y L. delawarensis, y encontramos que la presencia de astaxantina. Este mismo carotenoide fue el principal responsable de la coloración rosada en Sterna elegans, sin embargo estuvo acompañado de otros carotenoides (ej. cantaxantina y seazantina). En las diferentes gaviotas estudiadas se encontró que los carotenoides se encontraban dentro de la pluma y no presentes en la superficie de estas o en el aceite de la glándula uropigial, como se había previamente especulado. Nuestra hipótesis es que algunas gaviotas adquieren un plumaje rosado a consecuencia de la dieta ingerida durante el periodo de crecimiento de las plumas. Es tentador tratar de atar el color rosado en gaviotas como L. delawarensis a partir del 1990 con la introducción de astaxantina sintética en la dieta de salmones criados en cautiverio

Positive Carotenoid Balance Correlates with Greater Reproductive Performance in a Wild Bird

Background: Carotenoids can confer somatic and reproductive benefits, but most evidence is from captive animal experimentation or single time-point sampling. Another perhaps more informative means by which to assess physiological contributions to animal performance is by tracking an individual’s ability to increase or sustain carotenoids or other health-related molecules over time, as these are likely to be temporally variable. Methodology/Principal Findings: In a field study of North American barn swallows (Hirundo rustica erythrogaster), we analyzed within-individual changes in carotenoid concentrations by repeatedly sampling the carotenoid profiles of individuals over the course of the breeding season. Our results demonstrate that carotenoid concentrations of individuals are temporally dynamic and that season-long balance of these molecules, rather than single time-point samples, predict reproductive performance. This was true even when controlling for two important variables associated with reproductive outcomes: (1) timing of breeding and (2) sexually selected plumage coloration, which is itself positively correlated with and concomitantly changes with circulating carotenoid concentrations. Conclusions/Significance: While reproduction itself is purported to impose health stress on organisms, these data suggest that free-ranging, high-quality individuals can mitigate such costs, by one or several genetic, environmental (diet), or physiological mechanisms. Moreover, the temporal variations in both health-linked physiological measures and morphological traits we uncover here merit further examination in other species, especially when goals include the estimation of signal information content or the costs of trait expression