Researchers in Australia have found that several species of birds appear to be shrinking.

The Australian National University carried out a study into how birdlife has changed over the last century and found that many varieties are smaller than they once were.

Indeed, eight species were said to be between two and four per cent smaller than they were 100 years ago.

Dr Janet Gardner, one of the researchers behind the study, believes the birds are reducing in size because they are adapting to the effects of climate change, thereby reducing the costs of heat stress.

"How much and how rapidly a species can change in response to rising temperatures remains to be answered," she commented.

Dr Gardner stated that she would like to look at a broader range of species to see if the same pattern of size changes is apparent.

This comes after researchers from Imperial College London found that a similar trend is taking place among Soay sheep in the Outer Hebrides.

A study found that this is because milder winters caused by climate change are enabling smaller sheep to survive.