Scientists understand why birds change their color with the course of evolution

There are two theories. First, the mechanisms that allow organisms to adapt well to their

current environment, and the mechanisms that allowchange adaptations are different—the latter are suppressed as organisms become better and better suited to their current conditions. Therefore, adaptations are activated only when the environment changes.

Second, the mechanisms that force organisms to fit into the current environment themselves change during evolution.

It is difficult to distinguish between these possibilities becauseIn evolutionary biology, we necessarily study processes that occurred in the past, events that we missed. Instead, we conclude that we have missed out on comparing species that exist today. While this approach can tell how well living organisms fit into their current environment, it cannot tell how they got there. 

Alex. Badyaev, professor of ecology and evolutionary biology at the University of Arizona

Badyaev and his team were eager to observeadaptation to new conditions in action, paying special attention to the mechanisms involved. For this they chose a domestic finch. This bird has spread over most of North America over the past century and now occupies the largest ecological range of any existing bird species.

These birds color themselves by eating and integrating pigmented molecules called carotenoids into their feathers.

Carotenoids are large molecules, they fillfeathers of birds, as a result, their appearance and structure change. In feathers where structural integrity is important, such as temperature-regulating down or flight feathers, mechanisms develop that inhibit feather growth by incorporating carotenoids. For this reason, flight or down feathers are almost never colorful in any species of bird. At the opposite end of the spectrum, ornamental feathers benefit from being colorful and developing mechanisms that alter their structure to allow for greater carotenoid incorporation and improve their appearance.

Sources of carotenoid pigments in householdfinches vary. In local desert populations, finches get their pigments from pollen and cactus fruits, while in urban populations they get them from newly introduced plant species and bird feeders. In northern populations, they contain pigments from grass seeds, buds and berries.

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