All About Feathers

Unique to birds and their dinosaur ancestors, feathers have evolved into impressive biological structures that come in a surprising diversity of colors and forms. Here, we cover the breadth of feather biology by looking at feathers from a variety of scientific viewpoints including their anatomy, function, development, and evolution.

Amazon Parrot tail feather illustration by Andrew Leach

From the fluffy down on a swan chick to the brilliant spiral on a King Bird-of-Paradise tail, feathers are remarkable not just in the way they look to the naked eye, but also for their intricate microstructure. Understanding feather anatomy at the microscopic level provides insight into how feathers function. For example, the interlocking Velcro-like structure on many bird feathers creates the smooth, flexible, and resilient surface that supports flight and sheds water.

As feathers grow, they mature into highly branched structures. Careful study of this process inspired new hypotheseshypothesisan explanation that is testable through study and experimentation about the evolution of feathers through stages of increasing complexity. Newly unearthed dinosaur fossils from China and Canada have supported these hypotheses by providing specimens from each stage in the proposed evolutionary history—a clear example of how investigating biological structures across contexts can create scientific breakthroughs.

Feather Science From Many Angles

Thorough understanding of biological structures like feathers requires examination from many angles. We now recognize that how feathers function is intricately connected to how they’re structured, and how they grow is closely linked to how they evolved.

Tinbergen, via Wikimedia Commons
Niko Tinbergen, a 1973 Nobel Prize winner for his work to understand animal behavior, developed what he called the four levels of analysis that biologists have been using ever since to structure their research. For us to fully understand anything in nature, he said, we need to think about these four questions:

  • How does it work? (mechanism)
  • How does it function? (adaptation)
  • How does it develop? (development)
  • How did it evolve? (evolution)

Here we have taken Tinbergen’s advice and explored each of these questions to give you a comprehensive understanding of feather biology.

Fiery-throated Hummingbird detail - photo by Joseph F. Pescatore
Photo: Fiery-throated Hummingbird by Joseph F. Pescatore