Picky Birds Weigh and Listen to Peanuts to Choose the Best Ones to Eat

It turns out that birds don't like expending unnecessary amounts of effort. Scientists have found that some birds actually detect how good the food inside nuts are by weighing them before cracking them open.

Humans can detect when one object is heavier than another by moving the items up and down several times and focusing on the "feeling" of heaviness that they perceive. In this case, scientists found that Mexican Jays may be able to "weigh" peanuts and even listen to peanuts while handling them in their beaks, similar to humans knocking on a melon and listening to detect its quality.

"When we presented the jays with ten empty and ten full identically looking pods, we noticed that after picking them up the birds rejected the empty ones and accepted the full peanuts without opening them," said Sang-im Lee, one of the researchers, in a news release.

The researchers conducted a series of experiments, using slow motion videos to see what happens when the bird is deciding whether or not to drop or take away the peanut pod. They found that the birds shake the nuts in their beaks, which may provide them with the information similar to the feeling of heaviness. The jays also shake the nuts in their beaks and produce sounds by opening and closing their beaks around the peanut shell for brief moments. The scientists believe that this may produce sounds which tell the birds about the quality of the nut.

The findings reveal that bird are picky when it comes to what they eat. By determining the quality of a nut, then can avoid expending effort on nuts that aren't worth their time.

The findings are published in the Journal of Ornithology.

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