The Fascinating Discovery Behind The Color-Changing Woodpecker

The mystery of the color-changing woodpecker has been solved. For years, scientists have been puzzled by the striking appearance of certain yellow-shafted northern flickers (Colaptes auratus auratus), a common type of woodpecker. Up to one-third of these birds have been observed flaunting reddish and orange plumage, raising questions about their origins and possible genetic influences. A leading theory suggested that hybridization with the western red-shafted flicker, known for its vibrant coloration, was responsible. These two subspecies interbreed where their ranges overlap in the western Great Plains and eastern Rockies, resulting in a spectrum of colors from orange to salmon pink.

However, the intriguing discovery came when these unusually colored flickers were spotted far outside their expected ranges, particularly in the Northeast and along the eastern Seaboard, where the western subspecies was not previously thought to exist. This unexpected finding begged the question: what could explain this colorful enigma? Researchers turned their attention to the diet of these birds, leading to surprising revelations.

Jocelyn Hudon, the curator of ornithology at the Royal Alberta Museum, formulated a hypothesis regarding the reddish hue of these flickers. She suggested that the coloration was linked to pigments found in the berries of two invasive shrubs, namely Tartarian and Morrow's honeysuckle, which were introduced from central Asia and Japan. Studies conducted by Hudon and colleagues, including ornithologist Robert Mulvihill and Professor Alan Brush, indicated that when cedar waxwings feast on these berries, their feathers can take on an orange hue due to the pigments present in the fruit. This phenomenon was also noted in yellow-breasted chats, which can exhibit a slight orange tint after consuming honeysuckle berries.

In a recent study published in the journal The Auk, Hudon and her team confirmed that the red coloration in the flickers indeed stems from a pigment called rhodoxanthin found in these exotic honeysuckle berries. This pigment is chemically distinct from the compounds responsible for the vibrant colors observed in western red-shafted flickers, which are known as 4-keto-carotenoids. Interestingly, rhodoxanthin resembles the chemicals that produce yellow hues and appears to replace them, also inhibiting the production of yellow pigments.

Hudon noted the irony in this situation, as these honeysuckles were initially introduced in the 1960s with the noble intention of enhancing wildlife habitats. "A species introduced with good intentions is messing up the coloration of birds," she remarked, highlighting the unforeseen consequences of human actions on natural ecosystems.

Pigments in feathers are typically derived from a bird's diet. Bill Moore, a professor emeritus at Wayne State University, discovered that when raising birds in a controlled environment, feathers that usually have color appear white unless the birds consume foods containing the necessary pigments. This study underscores the connection between diet and avian coloration.

While it's uncommon for invasive plant species to alter bird coloration, this phenomenon has now been documented in flickers, cedar waxwings, yellow-breasted chats, and other bird species. The implications of this color change are significant, as noted by Moore. The bright feathers of these birds play a crucial role in mate selection; they are often used to signal genetic fitness, which indicates how healthy and attractive an individual is to potential mates. Unfortunately, these new colors could pose challenges for flickers and other birds, potentially affecting their chances in the mating game.