Carotenoids in nestling Montagu’s harriers: variations according to age, sex, body condition and evidence for diet-related limitations

Abstract

Carotenoids are colored pigments forming the basis of many avian social traits. Before their utilization carotenoids must be acquired through diet and mobilized for specific uses. The relationships between carotenoid-based coloration, circulating carotenoids and body condition have been well studied in adult birds, but little is known in nestlings. Here, we investigated variations in carotenoid-based coloration in a raptor nestling, the Montagu's harrier (Circus pygargus), both in captivity and in natural conditions, and within a vole (poor-carotenoid source and cyclic prey) specialist population. We studied these variations according to nestling age and sex, and possible limitations in carotenoid availability by comparing years of contrasted prey abundance and using carotenoid supplementation experiments. Captive nestlings, fed only with mice, were strongly carotenoid limited. Wild nestlings were also carotenoid limited, especially in a year of high vole abundance. Nestlings were in better condition but less colored during a peak vole abundance year than during a low vole abundance year, when harriers targeted more alternative preys (birds, insects). Thus, variation in vole abundance resulted in a de-coupling of body condition and carotenoid-based coloration in this population. This suggested that the positive relation between the body condition and carotenoid-based traits, typically found in adult birds, could be restricted to adults or nestlings of species that feed on carotenoid-rich food. Our results should stimulate more work on the functions and mechanisms of carotenoid-based traits in nestlings, which deserve more attention and most likely differ from those of adult birds.

Need and Seek for Dietary Micronutrients: Endogenous Regulation, External Signalling and Food Sources of Carotenoids in New World Vultures

“…The carotenoid profile in plasma of predatory and scavenger raptors showed a predominance of xanthophylls (∼90%), especially lutein, and traces of other carotenoids [11], [12], [20], [43], [44]. In this study, we found an unexpectedly large variety of carotenoids in plasma of Andean condors and American black vultures, two scavengers that mostly feed on herbivore mammal carcasses in varying states of decomposition [24], [25], [30].…”

Male Red-backed Fairywrens appear to enhance a plumage-based signal via adventitious molt

“…Juvenile birds can also convey condition via leg coloration, as in storks and raptors (Negro et al 2000, Casagrande et al 2009, Sternalski et al 2010, and the UV reflectance of nestling skin appears to be a signal that influences parental feeding (Jourdie et al 2004, Bize et al 2006. Juvenile American Coots (Fulica americana) display bright red skin on their head as well as orange feathers, which both appear to have evolved via parental favoritism for colorful chicks (Lyon et al 1994).…”

Disentangling the effects of environmental conditions on wintering and breeding grounds on age‐specific survival rates in a trans‐Saharan migratory raptor

“…about a week before fledging (note that some nests were fenced to protect them from harvesting activities, which also reduces predation risk before fledging). This pigment is involved in the immune response and birds with higher levels may be fitter (Sternalski et al 2010(Sternalski et al , 2012. Unexpectedly, the effect of mean breeding success was negative, meaning that juveniles experienced lower survival when born in years with higher mean breeding success (i.e.…”