The birds are getting smaller because of climate change

The weight and wings of hundreds of birds are decreasing due to global warming.

Pink chestbills.Photo: bobnaturephoto.com.

Bergman's law in biology affirms: The higher the ambient temperature, the smaller the size of the animal. Therefore, the species that live in the northern latitudes are usually larger in size than those that live in low latitudes.

The reason why Bergman's law happened is still a mystery. However, it makes some scientists question: Does the size of an animal change according to global warming?

According to BBC, to find out, Dr. Josh Van Buskirk of the University of Zurich in Switzerland and Robert Mulvihill, Robert Leberman - two experts of the Carnegie Museum of Natural History in Rector City, Pennsylvania, USA - decided to study Save the size of some 486,000 birds of 102 species that were captured by scientists during their journey through the state of Pennsylvania between 1961 and 2007.

The results showed that the weight loss and wingspan length showed in 60 migratory birds in the spring, 75 species migrated in the fall, 51 species migrated in the summer and 20 species migrated in the season. east for a period of 46 years.

In fact, the weight loss and wingspan in the bird are negligible.

'On average, the body weight of spring migratory species only decreased by 1.3% in 46 years. For a warbler weighing 10 g, the weight only decreased by 130 mg , 'Dr. Buskirk said.

But the size reduction in many species is greater than the above. For example, weight loss rates in pink-breasted big beaks are about 4%.

'Our research shows the body size of many North American birds, mostly songbirds, which are decreasing,' the BBC quoted Dr. Buskirk.

The reduction in body size has affected at least 20 generations of birds. However, their number did not decrease. This suggests that North American birds are following Bergman's rule by shrinking their bodies when temperatures rise.

The three researchers do not know whether the tendency to reduce the size of the body will cause any long-term consequences for birds.

'Many previous studies have shown that some species will benefit and some will suffer badly when temperatures rise. We cannot know in advance which species will be affected , ' Buskirk said.

Buskirk said that scientists need to collect more data to confirm this trend and find out if the downward trend can happen to other animals.