Carotenoids are a class of pigments which are widely used by animals for the expression of yellow-to-red colour signals. such as bill or plumage colour. Since they also have been shown to promote immunocompetence and to function as antioxidants. many studies have investigated a potential allocation trade-off with respect to carotenoid-based signals within the context of sexual selection. https://atlanticknifers.shop/product-category/collections/