Climate change is making birds smaller and threatening their lives — study

Photo by: petrovaliliya / iStock

One of the consequences of rapid climate change has been the shrinking size of birds. This is the conclusion reached by scientists at the University of California, USA, reports Phys.org.

The study found that over the past 30 years, the body weight of 105 of the feathered species examined has decreased by an average of 0.6%, and by 3% for some species. For example, tree swallows became lighter by 2.8%, American robins by 1.2% and downy woodpeckers by 2.2%.

At first glance, the changes do not seem major, but in terms of evolution, the process is very fast.

The scientific report describes how much temperature affects the physical characteristics of living creatures.

According to ecologist Morgan Tingley, a large number of species have been affected by the decline in size, suggesting that the trend is caused by a global process such as climate change. If the cases were private, the cause could be blamed on less significant factors.

Smaller bodies help birds cope with rising temperatures because a higher surface area to volume ratio helps dissipate heat. Conversely, larger and rounder bodies, typical of birds in colder regions, retain temperature better.

The study showed that the size of the birds varies predictably according to location. Birds in warmer regions tend to be smaller than their counterparts in colder areas.

It has also been found that in warmer areas the birds start to become smaller relatively quickly.

Despite signs of adaptation, scientists are concerned about the future of the birds. The decline in size cannot keep up with the rate of warming. Given the rate at which global average temperatures are rising, the decline in bird body mass is only 40 per cent of what biologists expect. This means the creatures are at greater risk of overheating, dehydration and death.

Another curious finding was that the shrinking trend did not affect the size of the birds’ wings and they became larger relative to their body size.

Morgan Tingley suggested that wings have almost no effect on a bird’s ability to get rid of excess heat. There are legs and a beak for that.

Researchers have discovered another factor influencing the size and shape of birds. The report provides the first large-scale evidence that birds living at higher altitudes tend to have longer wings, an adaptation that helps them fly in the thin air of mountains. In these places, birds have longer wings and smaller bodies despite the lower temperatures.

Cover photo: Andrey Zhuravlev / iStock