Antibiotic treatment increases yellowness of carotenoid feather coloration in male greenfinches (Chloris chloris)

Carotenoid plumage coloration is an important sexually selected trait in many bird species. However, the mechanisms ensuring the honesty of signals based on carotenoid pigments remain unclear. It has recently been suggested that intestinal integrity, which is affected by gut parasites and microbiota and influences nutrient absorption and acquisition, mediates the relationship between carotenoid ornamentation and individual quality. Here, we test whether carotenoid plumage coloration in greenfinches (Chloris chloris) is affected by the treatment of an antibiotic or an antiparasitic drug. We captured wild greenfinches (N = 71) and administered anticoccidial medication toltrazuril (TOLTRA) to one group, antibiotic metronidazole (METRO) to the second group to target trichomonosis, and the third group received no medication. In the METRO group, feathers grown during the experiment had significantly higher chroma of yellow parts, but there was no effect of TOLTRA on feather chroma. The results suggest that METRO increased the efficiency of carotenoid modification or deposition to the feathers rather than nutrient acquisition and/or freed energy resources that could be invested in coloration. Alternatively, though not measured, METRO might have affected microbial community and host physiology as microbial metabolites can modulate mitochondrial and immune function.

Antibiotic treatment increases yellowness of carotenoid feather coloration in greenfinches (Chloris chloris)

Carotenoid plumage coloration is an important signal of quality, and plays an important role in mate choice in many bird species. However, it remains unclear what mechanism makes carotenoids an honest signal. Here, we test the hypothesis that carotenoid plumage coloration might indicate gut health. Parasitic and microbial infections can affect nutrient absorption due to decreased gut surface or by altered gut microbiome. We took an advantage of a naturally occurring coinfection of parasites inhabiting the upper and lower portions of the digestive track to distinguish between the direct and indirect effects of parasites on carotenoid acquisition. Protozoan coccidian intestinal parasites are widespread in greenfinches (Chloris chloris) and the majority of greenfinches are infected in nature. Trichomonosis is an emerging disease of the upper digestive track that causes high mortality among greenfinches. We captured wild greenfinches (N=71) and administered anticoccidial medication toltrazuril (TOLTRA) to one group, antibiotic metronidazole (METRO) that is also effective for treating Trichomonas gallinea, to the second group, and third group received no medication. In the METRO group, feathers grown during the experiment had significantly higher chroma of yellow parts, but there was no effect of TOLTRA on feather chroma. These results suggest that METRO increased the efficiency of carotenoid modification or deposition to the feathers rather than nutrient acquisition, and/or freed energy resources that could be invested in coloration. Alternatively, in accordance with shared pathway hypothesis, increase in efficiency of vital cellular processes might have occurred, as many microbial metabolites can modulate mitochondrial and immune function.

The identity of Azara’s description No. 18 “Gavilán mixto pintado” is a juvenile Harris’s hawk (Parabuteo unicinctus)

The classic ornithological work by Félix de Azara “Apuntamientos para la historia natural de los páxaros del Paraguay y Rio de la Plata” was one of the first descriptive texts dealing with the avifauna of the Southern Cone of South America. Azara’s No. 18 “Gavilán mixto pintado” has long been misidentified as a juvenile great black hawk (Buteogallus urubitinga ((Gmelin, 1788)). However, there are clear inconsistencies in the description of the plumage coloration, shape and measurements which make that identification erroneous, and Azara’s No. 18 can in fact be convincingly identified as the juvenile plumage of the Harris’s hawk (Parabuteo unicinctus (Temminck, 1824)). The description by Azara contains numerous diagnostic characteristics for that species, and the measurements provided by him are inconsistent with those of the great black hawk, yet remarkably similar to those provided by the same author for the description of the adult No. 19 “Gavilán mixto obscuro y canela”. No scientific names have apparently ever been based on Azara No. 18.

Sex-specific relationships between urbanization, parasitism, and plumage coloration in house finches

Historically, studies of condition-dependent signals in animals have been male-centric, but recent work suggests that female ornaments can also communicate individual quality (e.g., disease state, fecundity). There also has been a surge of interest in how urbanization alters signaling traits, but we know little about if and how cities affect signal expression in female animals. We measured carotenoid-based plumage coloration and coccidian (Isospora spp.) parasite burden in desert and city populations of house finches Haemorhous mexicanus to examine links between urbanization, health state, and feather pigmentation in males and females. In earlier work, we showed that male house finches are less colorful and more parasitized in the city, and we again detected such patterns in this study for males; however, urban females were less colorful, but not more parasitized, than rural females. Moreover, contrary to rural populations, we found that urban birds (regardless of sex) with larger patches of carotenoid coloration were also more heavily infected with coccidia. These results show that urban environments can disrupt condition-dependent color expression and highlight the need for more studies on how cities affect disease and signaling traits in both male and female animals.

De Novo Assembly of the Northern Cardinal (Cardinalis cardinalis) Genome Reveals Candidate Regulatory Regions for Sexually Dichromatic Red Plumage Coloration

Northern cardinals (Cardinalis cardinalis) are common, mid-sized passerines widely distributed in North America. As an iconic species with strong sexual dichromatism, it has been the focus of extensive ecological and evolutionary research, yet genomic studies investigating the evolution of genotype–phenotype association of plumage coloration and dichromatism are lacking. Here we present a new, highly-contiguous assembly for C. cardinalis. We generated a 1.1 Gb assembly comprised of 4,762 scaffolds, with a scaffold N50 of 3.6 Mb, a contig N50 of 114.4 kb and a longest scaffold of 19.7 Mb. We identified 93.5% complete and single-copy orthologs from an Aves dataset using BUSCO, demonstrating high completeness of the genome assembly. We annotated the genomic region comprising the CYP2J19 gene, which plays a pivotal role in the red coloration in birds. Comparative analyses demonstrated non-exonic regions unique to the CYP2J19 gene in passerines and a long insertion upstream of the gene in C. cardinalis. Transcription factor binding motifs discovered in the unique insertion region in C. cardinalis suggest potential androgen-regulated mechanisms underlying sexual dichromatism. Pairwise Sequential Markovian Coalescent (PSMC) analysis of the genome reveals fluctuations in historic effective population size between 100,000–250,000 in the last 2 millions years, with declines concordant with the beginning of the Pleistocene epoch and Last Glacial Period. This draft genome of C. cardinalis provides an important resource for future studies of ecological, evolutionary, and functional genomics in cardinals and other birds.