Sunlight's Surprising Effect on Eagle Feathers

Spanish imperial eagles start life with bright orange feathers. But over time, these feathers change color. This is not because they grow new feathers. It is because of sunlight. Scientists studied this effect. They took feathers from young eagles. Then, they put these feathers in the sun for 15 weeks. They watched how the feathers changed. The feathers got brighter. They also got paler. After 15 weeks, the feathers were almost two times paler. The feathers also lost some of their strength. This change happens to young eagles in nature. Their feathers go from dark orange to yellow. This happens in the first few months of their life. They do not grow new feathers. The sunlight changes the color.This change is called photobleaching. It is when sunlight breaks down the pigments in the feathers. These pigments are called melanins. They are common in animals. Young eagles keep their bleached feathers for years. Their feathers turn black when they are older. This happens after they grow new feathers. This takes about 5-6 years. During this time, the feathers are weaker. This might make it harder for the eagles to fly. It might also affect how they hide from predators. Other birds also have this problem. Young birds of prey often have feathers that fade. So do some other birds. For example, wheatears. Their feathers fade without growing new ones. This fading might affect how birds live. It might help them hide. It might also affect when they migrate. Scientists are still studying this.