December 10, 2019
Estimates suggest as many as a billion birds die each year as a consequence of flying into buildings. While this is undoubtedly a tragedy, one man has been able to find an interesting silver lining. Over a period of 40 years ornithologist Dave Willard collected 70,716 birds from Chicago and has now personally collected measurements from each of these specimens.
From this data he has been able to determine that over this period of time North American migratory birds have changed. Their body size has been getting smaller, and their wings have been getting longer. During this same 40-year period the Earth has been getting warmer as a consequence of the climate crisis. Willard and University of Michigan assistant professor Brian Weeks believe this warming is responsible for the changes seen in the birds.
The increased temperatures, they say, may mean the birds need less body mass in order to stay warm, which could help explain why their bodies have become smaller over time. However, this smaller body size means that migration uses up more energy, so to compensate their wings are becoming longer to make flight more energy efficient. This is a fascinating example of evolution in response to our changing climate.
Source: Popular Mechanics
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