Wild common crossbills produce redder body feathers when their wings are clipped

• Published in: BMC Zoology
• Main Authors: Blanca Fernández-Eslava, Alejandro Cantarero, Daniel Alonso, Carlos Alonso-Alvarez
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2022
• Subjects: Animal coloration; Carotenoid-based ornaments; Flying effort; Flight workload; Shared-pathway hypothesis; Sexual signaling; Zoology; QL1-991; Avian Studies
• Online Access: https://doi.org/10.1186/s40850-022-00150-9; https://doaj.org/article/bde81ea30ca849ebbaade60971dc0340

Abstract Background The animal signaling theory posits that conspicuous colorations exhibited by many animals have evolved as reliable signals of individual quality. Red carotenoid-based ornaments may depend on enzymatic transformations (oxidation) of dietary yellow carotenoids, which could occur in the inner mitochondrial membrane (IMM). Thus, carotenoid ketolation and cell respiration could share the same biochemical pathways. Accordingly, the level of trait expression (redness) would directly reveal the efficiency of individuals’ metabolism and, hence, the bearer quality in an unfalsifiable way. Different avian studies have described that the flying effort may induce oxidative stress. A redox metabolism modified during the flight could thus influence the carotenoid conversion rate and, ultimately, animal coloration. Here, we aimed to infer the link between red carotenoid-based ornament expression and flight metabolism by increasing flying effort in wild male common crossbills Loxia curvirostra (Linnaeus). In this order, 295 adult males were captured with mist nets in an Iberian population during winter. Approximately half of the birds were experimentally handicapped through wing feather clipping to increase their flying effort, the other half being used as a control group. To stimulate the plumage regrown of a small surface during a short time-lapse, we also plucked the rump feathers from all the birds. Results A fraction of the birds with fully grown rump feathers (34 individuals) could be recaptured during the subsequent weeks. We did not detect any significant bias in recovery rates and morphological variables in this reduced subsample. However, among recaptured birds, individuals with experimentally impaired flying capacity showed body mass loss, whereas controls showed a trend to increase their weight. Moreover, clipped males showed redder feathers in the newly regrown rump area compared to controls. Conclusions The results suggest that wing-clipped individuals could have endured higher energy ...