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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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Nest choice after migration in Mediterranean storm petrels

Nest choice after migration in Mediterranean storm petrels

Petrels are highly philopatric and return from migratory journeys of thousands of kilometres to breed in the same burrow year after year. During the breeding season, some burrowing petrel species rely on their sense of smell to locate their nest at night, but the mechanisms involved in the homing behaviour after several months at sea are virtually unknown. To understand whether the sense of smell is involved in nest finding at the return from migration and to study the interplay with other positional cues, the homing behaviour and nest choice by Mediterranean storm petrels was explored. During two consecutive winters, research was conducted in a colony with well-used artificial nestboxes that has been studied for the past two decades. Previously occupied nestboxes were experimentally displaced in late winter and then checked for nest choice and occupancy by breeding individuals in the following breeding season. Almost all individuals nested in the nestbox located at the same position as the year before, regardless of whether the nestbox was the one they had previously occupied or another one. During the breeding period, the olfactory preference for the occupied nestbox with respect to another random one was also tested. Again, storm petrels did not show any olfactory preference for their nest. This study implies that storm petrels rely on other positional cues than olfactory ones to home and suggests a mechanism combining tactile and proprioceptive cues to find the nest in the dark. informacion[at] Dell'Ariccia G et al 2015 Mediterranean storm petrels rely on nest position for homing after migration: a test with artificial nest-boxes Anim Behav 107:97-104. DOI information: 10.1016/j.anbehav.2015.06.010