Birds Show Fruit Color Pecking Order

Study shows that birds prefer red and black over other fruit colors, suggesting that bird preferences may have influenced fruit color evolution.

AsianScientist (Jul 17, 2014) – A study published in Scientific Reports shows that tropical Asian birds seem to favor red and black fruits, suggesting that fruit color evolution is partially influenced by bird preferences.

Red and black are the most common colors for fleshy fruits distributed by birds, leading to the hypothesis that plants produce fruits in those colors to attract birds. To date, however, there have not been studies which definitively prove this idea.

Although birds have excellent color vision which they might use to locate fruit, they may select fruit for its nutritional content rather than color. Similarly, plants may have evolved certain colors due to positive selection for pigments which are unrelated to their attractiveness to birds. For example, anthocyanins protect vegetative tissue and prevent fungal growth.

In order to evaluate the color preferences of birds, Professor Quan Rui-Chang from the Xishuangbanna Tropical Garden under the Chinese Academy of Sciences tested the behavior of four species of fruit eating birds in response to artificial and natural fruit of five different colors. Artificial fruits were made from a mixture of apple, pear, banana, wheat and corn flour, and were dyed black, red, yellow, green or blue, matching the colours of the natural ripe fruits used.

“My first finding from this study was working with young birds is not easy: they need to be constantly fed and carefully tended!” Prof. Quan told Asian Scientist Magazine. “But really the most interesting finding was that these hand-raised birds more accurately reflected the colors of fruit found in nature, more than the wild-caught adults. Indeed, the hand-raised birds preferred black natural fruits, which are the most common color.”

“It is makes sense from an evolutionary perspective that young birds should innately prefer common fruit colors as this would quickly lead them to find food. In contrast, adults have had a lot of experience with fruit and may select fruit based on many different characteristics, not just color,” he explained.

Prof. Quan intends to further his study on seed dispersal in birds by next looking at how seeds are effected by passing through the gut, with birds in aviaries at the Xishuangbanna site.

“Recently, my colleagues and I have also put videocameras on wild bird nests, which will allow us to observe food selection at a critical time for the nestlings’ survival,” he said.

The article can be found at: Duan et al. (2014) Bird Fruit Preferences Match the Frequency of Fruit Colours in Tropical Asia.


Copyright: Asian Scientist Magazine; Photo: Tatters/Flickr/CC.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Rebecca did her PhD at the National University of Singapore where she studied how macrophages integrate multiple signals from the toll-like receptor system. She was formerly the editor-in-chief of Asian Scientist Magazine.

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