Ornithologists have figured out why many birds have become smaller in recent decades

(ORDO NEWS) — Over the past three decades, the body size of many species of North American birds has decreased – by only a fraction of a percent, but these are very rapid changes in such a short period from an evolutionary point of view.

Now scientists have discovered who or, more precisely, what is to blame for the fact that quite ordinary swallows and blackbirds “decided to become” hummingbirds.

For birds that spend a lot of time in flight, even a slight change in body weight speaks volumes.

A study by scientists at the University of California, Los Angeles (USA) showed that over the past three decades, the body weight of 105 considered species of North American birds has decreased by an average of 0.6 percent, and in some species by 3.0 percent.

These figures may seem insignificant, but it is worth considering that, from the point of view of evolution, 30 years is less than an instant, and the fact that changes have affected a variety of species occupying different ecological niches indicates a certain global impact on all birds.

And researchers suspect that global warming is to blame for the decrease in birds.

The fact is that in warmer climates, it is more advantageous for large animals to become smaller, because a higher ratio of surface area to volume helps to remove heat.

But in cold regions, on the contrary, animals become larger and “rounder” in order to maintain body temperature and not freeze.

Birds that “lose mass” fastest are those living in the warmer regions of North America, but even there, the decrease in their size was only 40 percent of the indicators that birds should achieve based on increased temperatures.

In other words, animals are not keeping up with the climate, and if the pace of global warming continues, this could lead to mass death of birds from overheating.

The overall reduction in body size has hardly affected the size of the wings, probably because, covered with insulating feathers, they are useless for generating or dissipating heat.

It is also possible that larger wings will allow birds to spend less effort on flight and, as a result, produce less heat.

In today’s world, which is warming up much faster than the evolution of most living things, bird adaptations are a cool drop in a boiling sea, but they prove that animals are much more plastic than we think they are.

Suffice it to reduce the rate of global warming, and then our neighbors on the planet will have more time to adapt, which can save dozens of species of living beings.


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