The Girl With The Skeleton Hand

The Girl with the Skeleton Hand

Now You Know (Source)

aphroditehell

“When we presented the jays with ten empty and ten full identically looking pods (pods without or with three nuts inside), we noticed that after picking them up the birds rejected the empty ones and accepted the full peanuts, without opening them.” says Dr. Sang-im Lee of Seoul National University – the corresponding author of the paper. A series of similar experiments with identically looking normal nuts and nuts that were 1g heavier (pods with some clay added) confirmed that jays always were able to distinguish and preferred the heavier nuts. How did they know which were empty without opening them? The researchers used slow motion videos to see what happens when the bird is deciding whether to drop or take away the peanut pod. “We found out that birds shake the nuts in their beaks. We think that these movements may provide them with the information generally similar to our feeling of "heaviness” when we handle an object in our hands", says Dr. Jablonski.

In another experiment the researchers prepared one type of peanut pods by opening the shell, removing two out of the three nuts and closing the shell again. The second type of pod was prepared by opening a small pod, which normally contains only one nut, and closing it. Thus, the jays were to choose between nuts of similar content and mass but of different size. “The jays figured out that the larger pods did not weigh as much as they should and the birds preferred the smaller pods, which weighed as expected for their size”, comments Dr. Fuszara. They behaved as if they knew that “something is wrong” with the larger nuts.

So how do they know it? When they shake the nuts in their beaks, the birds produce sounds by opening and closing their beaks around the peanut shell for brief moments. The researchers think that the jays also take this sound into account.