A new study, which was published in the Journal of Ornithology, has found that some birds are weighing peanuts, and then choosing the heavier ones to eat. Since most of the food that animals such as birds eat have shells, it’s hard to know what seeds and nuts are good, but this study is showing birds have their own way to determine the quality of the food inside of the shell.
The study was carried out by an International research team from Korea and Poland in Arizona, and it revealed how Mexican Jays can weigh and listen to peanuts when handling them in their beaks. The leading researchers for this study were Drs. Sang-im Lee, Piotr Jablonski, Maciej and Elzbieta Fuszara. The researchers along with students spent hours opening the shells of hundreds of peanuts, then changing the contents of them, and then presenting them to the Mexican Jays. The researchers wanted to know whether or not the birds would be able to figure out the differences in what was inside of the shells, with them looking identical in terms of the peanut pods, which is the peanuts in the shell. The researchers found out that when they presented the Mexican Jays with 10 empty peanut shells and 10 identically looking pods, the Mexican Jays would pick up and then put down the empty ones. The Mexican Jays then went to the full peanuts without even opening them and accepted them, which was because the pods were fuller in terms of weight.
Another experiment was conducted with identically looking nuts that were normal and nuts that were 1 gram heavier, which contained clay or another product. The Mexican Jays were able to distinguish between which were the good nuts and which were the bad nuts, and then would choose the heavier nuts. The researchers then use a slow motion video in order to see what the Mexican Jays were doing during this process, and they found out that the birds would take the nuts and shake them in their beaks. The researchers determined this was how the birds were able to weight the nuts with their beaks, and that is how they can tell which nuts were empty or full of food. This is similar to people in terms of how we weight melons in our hands at the store, which helps us determine which melons are ripe and ready to eat.
The researchers also performed another experience by opening the shell of the peanut pods, removing a few nuts and then closed the shell. The second pod involved opening a small pod, which usually only has one nut, and then closing it again. The nuts were of almost the same content but they were different sizes, and the Mexican Jays once again weighed the nuts in order to pick out the best ones. The birds chose the smaller pods, which makes sense considering the bigger ones had been tampered with by the researchers and had nuts removed. The birds were able to weigh the pods and determine that the smaller ones were the weight they were supposed to be.
When the birds ended up shaking the nuts in their beaks, there was a sound produced from opening and closing the beak around the peanut shell. The researchers believe that this sound is what the Mexican Jays used to help them determine which of the peanuts were good and which ones were bad. The sound would be different from the smaller lighter nuts to the heavier nuts, and that helps the birds figure out which is heavier than the other. The researchers next want to find out if the sound is relative to the perception of heaviness in terms of the acorns, which are the natural food of the Mexican Jays. This study will be able to help researchers determine how other birds also use sound and weight to determine which products are good and safe to eat as opposed to products that might have been tampered with, either by people or other animals. If the researchers can find out that the Mexican Jays also use the same methods with the acorns, then this will help them in terms of tracking down more information about the responsibility of the beak of birds. There is a lot that is not known in terms of how birds use their beaks and what exactly the beaks help the birds do. The researchers are also hoping that this research can help in other parts of the bird world as well.