Scientists say that Arctic migratory birds are now shrinking literally in size, as temperatures become warmer in the northern polar region, according to a new study. Researchers believe that this is a direct effect of climate change, where the red knot may not be able to survive on other continents.

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During the summer, the shore bird begins breeding season and then migrates to warmer habitats in tropical regions during the winter. In this new study, scientists detail how this change in body size is a response by animals, triggered by climate change. 

The red knot also known as the Calidris canutus, is also a wading bird and currently holds one of the records for the longest distance flight during migration period without any breaks, at 5,000 kilometers. In this new study, an international team of scientists studied the bird for more than 30 years in Russia, where the bird stops during its migration.

According to Jan van Gils from the Royal Netherlands Institute for Sea Research and Utrecht University, there is this observable change in body size. Researchers say that they gave strong evidence that this is an effect of climate change, as others also observed these changes in body size, as a response to changing temperatures. This study also marks the first one to show that this response is a disadvantage to the animal's survival, since smaller birds have lower survival rates.

Apart from the birds' body size, researchers also discovered that snow melt rate in the Arctic has been moving to an earlier time by more than two weeks. Coinciding with this is the birds' offspring size, becoming smaller and smaller chicks that can be attributed to the chicks' missing out on the main source of food due to earlier thaw time.

New findings reveal that the red knot's diet during the winter consist of mollusks buried deep inside mud, however, only those who have longer bills can reach them. Those with shorter bills cannot reach the shellfish which drives them to a eat lesser amount and less nutritious food.

Van Gils adds that there are now fewer birds that develop into adulthood, where they are the ones that are small and have a longer bill. According to Martin Wikelski from the Max Planck Institute for Ornithology, these results show that long term changes in the body sizes of the Arctic wading birds can affect their survival especially during their migration to the tropics during winter time, that can have ecological consequences since their habitats are located halfway around the globe from each other.

This new study is published in the journal, Science. 

Tagsred knot bird, arctic bird, Arctic region, shrinking bird due to climate change, Climate Change, arctic wading bird, migratory birds