The research, conducted by biologists from the University of Wisconsin-Madison, analyzed the body size of kestrels over a span of four decades. The results showed that the birds have experienced a decline in body mass and size, with the average weight decreasing by 4.2% and the wing length decreasing by 2.4%.

The reasons behind the kestrel’s shrinking size are not yet fully understood, but the researchers believe it may be related to changes in their habitat and food sources. The bird primarily feeds on insects, small mammals, and reptiles, which may be affected by climate change and other environmental factors.

The decline in the kestrel’s size could have significant impacts on the bird’s ability to survive and reproduce. A smaller body size could make it more difficult for the bird to catch prey, and it could also lead to increased competition for resources among individuals.

The American Kestrel is already listed as a species of “High Concern” by the North American Bird Conservation Initiative due to population declines in some areas. The new research adds to concerns about the bird’s future and highlights the need for continued conservation efforts to protect its habitat and food sources.

While the kestrel’s shrinking size is concerning, the researchers note that it is not too late to take action to help the species. They suggest that efforts to create and maintain suitable habitat for the bird, as well as monitoring of its population and food sources, could help to mitigate the effects of environmental changes and ensure the survival of this important species.