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Impairment of mixed melanin-based pigmentation in parrots

Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated to pheomelanin synthesis, this study assumed that the latter would be avoided by psittaciform birds. This hypothesis was tested by using Raman spectroscopy to identify pigments in feathers exhibiting colors suspicious of being produced by pheomelanin (i.e., dull red, yellow and grey- and green-brownish) in 26 species from the three main lineages of Psittaciformes. The non-sulphurated melanin form (eumelanin) were detected in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but no evidence of pheomelanin was found. As natural melanins are assumed to be composed of eumelanin and pheomelanin in varying ratios, these results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. The study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity. informacion[at] Neves et al (2020) Impairment of mixed melanin-based pigmentation in parrots. J Experim Biol. DOI 10.1242/jeb.225912
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High livestock numbers have a negative influence on Canarian Egyptian vultures’ body condition

High livestock numbers have a negative influence on Canarian Egyptian vultures' body condition

Individual traits such as body mass can serve as early warning signals of changes in the fitness prospects of animal populations facing environmental impacts. Here, taking advantage of a 19?year monitoring, the question how individual, population and environmental factors modulate long?term changes in the body mass of Canarian Egyptian vultures was addressed. Individual vulture body mass increased when primary productivity was highly variable, but decreased in years with a high abundance of livestock. The hypothesis tested was that carcasses of wild animals, a natural food resource that can be essential for avian scavengers, could be more abundant in periods of weather instability (i.e. variation in primary productivity) but depleted when high livestock numbers lead to over?grazing. Results would also indicate that wild prey represents essential, but highly underestimated, resources, whose availability would affect vulture condition and fitness. In addition, increasing vulture population numbers also negatively affect body mass suggesting density?dependent competition for food. Interestingly, the relative strength of individual, population and resource availability factors on body mass changed with age and territorial status, a pattern presumably shaped by differences in competitive abilities and/or age?dependent environmental knowledge and foraging skills. This study supports that individual plastic traits may be extremely reliable tools to better understand the response of secondary consumers to current and future natural and human?induced environmental changes. Disentangling the complex relationships among ecosystem-level factors, population structure, and individual characteristics that determine animal body condition will help define management strategies for this and other ecologically similar endangered populations. informacion[at] Donázar et al (2020) Too much is bad: increasing numbers of livestock and conspecifics reduce body mass in an avian scavenger. Ecol Appl DOI 10.1002/eap.2125