https://ift.tt/2wwdHAe Parrots Think They’re So Smart. Now They’re Bartering Tokens for Food Birds, Animal Behavior, Animal Cognition Parrots can judge the relative value of food, holding out for tasty walnut slivers. JAMES GORMAN https://ift.tt/2oY5bTZ September 11, 2018 at 05:30AM

By JAMES GORMAN from NYT Science https://ift.tt/2wZS0Gq