Ann Arbor Times

For centuries, scientists have observed that animals in warmer climates tend to have longer limbs, a pattern known as Allen’s Rule. Traditionally attributed to maintaining body temperature, the exact mechanisms behind this pattern have been unclear. However, a new computer vision system has confirmed that this principle applies to bird wings as well. This finding reshapes the understanding of bird wing evolution by including temperature regulation alongside flight mechanics and may offer insights into how birds are adapting to climate change.

Brian Weeks, lead author of the study and assistant professor at the University of Michigan’s School for Environment and Sustainability, stated: “Collecting skeletal measurements on a large scale lets us answer big questions about how species evolve and interact with their environments.” The study was published in Global Ecology and Biogeography after six years of collaboration between ecologists and computer scientists at the University of Michigan and New York University.

The team developed "Skelevision," an artificial intelligence system that identifies and measures bird bones from photographs. David Fouhey, one of the senior authors from NYU Tandon School of Engineering and NYU's Courant Institute, explained: “We use a deep neural network to detect individual bones in specimen images, identify their type, and create a precise digital outline of each one.” This system simplifies 3D measurement into a 2D task using advanced computer vision systems.

Before this technology was available, researchers had to manually handle fragile bones for measurements. The Skelevision system combines physical imaging hardware with sophisticated AI software for analyzing bird skeletons efficiently. It reduces specimen handling time significantly—from about 15 minutes per sample to approximately one minute—demonstrating its accuracy across over 12,000 specimens as established in a 2023 report.

Researchers analyzed wing-bone measurements from 1,520 species of passerine birds across various continents using specimens primarily from the University of Michigan Museum of Zoology supplemented by Chicago’s Field Museum. Weeks highlighted that “wing bones play a unique role in thermoregulation,” emphasizing that muscles supported by these bones help dissipate heat generated during flight rather than conserving it.

The study also involved Christina Harvey from UC Davis; Joseph Tobias from Imperial College London; Catherine Sheard from the University of Bristol; Zhizhuo Zhou from both Carnegie Mellon University and the University of Michigan. Funding was provided by The David and Lucile Packard Foundation.

Looking forward, researchers plan to expand their technology with an advanced 3D scanning system to measure additional properties like volume and surface area while making their dataset publicly accessible along with open-source code.