Becca Safran, Matt Wilkins, Joey Hubbard and Julie Marling have published a paper in PLOS One, describing the dynamic nature of carotenoid concentrations in barn swallows, and relationships with fitness. Here is a link to the paper:
www.plosone.org/article/metrics/info%3Adoi%2F10.1371%2Fjournal.pone.0009420
Congratulations to the Safran Lab!
