Changes in Morphology of Migratory Birds

Environmental & Science Education

STEM

Climate Change

Biodiversity

Nature

Biological Evolution

Edward Hessler

Earth's life will react to global climate change but there are many questions on how--in what ways.. 

In a paper published in Ecology Letters (behind a subscription wall) this abstract of a paper reveals body size reduction in 52 North American migratory bird species. This is a subtle change which is not visible to the naked eye. It must be measured.

The scientists used "a four-decade specimen series of 70,716 individuals. Over the 40-year period studied there were "consistent reductions in body size" and an increase in wing length.  The authors write"Our findings suggest that warming-induced body size reduction is a general response to climate change" and "a similarly consistent and unexpected shift in body shape."

Science Daily provides more details than was available to me from the abstract of the published paper. Here are a few are highlighted.

--"Since 1978, Field Museum personnel and volunteers have retrieved dead birds that collided with Chicago buildings during spring and fall migrations."

--"The new study is the largest specimen-based analysis of body-size responses to recent warming, and it shows the most consistent large-scale responses for a diverse group of birds."

--One person, "David E. Willard, the Field Museum ornithologist and collections manager emeritus...measured all 70,716 birds analyzed in the study. ... For each bird, Willard measured the length of a lower leg bone called the tarsus, bill length, wing length, and body mass. In birds, tarsus length is considered the most precise single measure of within-species variation in body size."

--"Tarsus length declined 2.4% across species."

--"The authors of the Ecology Letters paper suggest that the body-size reductions are a response to climate warming and that increased wing length may help offset the body-mass losses.

​​"The researchers plan to test that idea in a follow-up project, which will again make use of the Field Museum dataset. They'll also look further into the mechanism behind the body size and shape changes and whether they are the result of a process called developmental plasticity, the ability of an individual to modify its development in response to changing environmental conditions.​​"