Songbirds shrinking due to climate change

The change has taken place within just half a century. The birds are evolving into a smaller size with the constant increase in atmospheric temperature, claimed the study conducted by Josh Van Buskirk of the University of Zurich, Switzerland and colleagues Robert Mulvihill and Robert Leberman.

Scientists explain the phenomenon with the help of the old biology rule, Bergman’s rule, which states that animals start shrinking in warmer climates.

Half a million birds studied
The study was conducted on approximately half a million birds from 100 different species, passing through the Carnegie Museum's Powdermill ringing station, in Pennsylvania, from 1961 to 2007.

Each bird was weighed; its wing length measured, as well as the wing chord length of the bird was recorded.

The data was constantly upgraded throughout the study period by the researchers.

Results of the study
The study has revealed that out of the 83 species migrating in spring, 60 have shrunk in size and weighed less than earlier.

Of the 75 species observed during autumn, 66 have grown smaller, and 51 out of the 75 species migrating during summer have been affected by climate change.

There is no evidence that this change is harmful to the birds as their population is not seen dwindling. The change might bring forth major problems in the near future.

The trend of the birds shrinking due to the climate change has been frequently noticed in birds living over a range of latitude or altitude, like the ones that winter in the New World tropics of the Caribbean, Central America and South America.

Details of the discovery are published in the journal Oikos.

Change harmless to birds
There is no evidence that this change is harmful to the birds as their population is not seen dwindling. The change might bring forth major problems in the near future.

Some recent research also suggests that few birds might be responding to the problems like the unavailability of food, rather than warm climate.

"In one obvious sense, the consequences are positive," says Buskirk.
"That is, as temperatures become warmer, the optimal body size is becoming smaller, however, even though the species appear to be adapting to the new climatic conditions, it could still be that their average "fitness" in evolutionary terms, is going down.”

"Evidence from other studies is that some species will benefit and others will be harmed, and it's not always the species we like that will be harmed," says Buskirk.