Final answer:
The change in the scarlet tanager's feather color from vibrant red in spring to a duller color in fall is due to seasonal changes, similar to how deciduous trees' leaves change color with less chlorophyll production in the fall.
Step-by-step explanation:
The change in color of the scarlet tanager from a vibrant red in spring to a less intense red in fall can be explained by seasonal changes affecting pigment production. In fall, environmental changes such as shorter days and cooler temperatures cause the bird to produce less of the vibrant red pigments, similar to how leaves produce less chlorophyll, allowing other pigments to become more visible. This is akin to how deciduous trees respond to the change in seasons with their leaves' color transitions from green to autumnal colors like orange, yellow, and brown.
Chlorophyll production decreases in plant leaves as days shorten, letting colors from other pigments become visible. For birds like the scarlet tanager, their feather pigmentation can also change due to hormonal variations that can be influenced by the length of the day.
Colors in nature can fade differently when exposed to the Sun, as blue and violet pigments have relatively higher photon energy and stability compared to reds, yellows, and greens, as indicated by experiments, such as one involving how different pigments in leaves respond to sunlight.