In research labs and wild habitats alike, plenty of animals have been observed gifting their friends with grub. Bonobos pass morsels of meat to strangers, vampire bats barf blood into hungry relatives’ mouths, and canines tap their snouts to touch screens to share sausages with packmates.⁠ ⁠ But Brucks and Auguste von Bayern, an animal behaviorist at the Max Planck Institute for Ornithology in Germany, wanted to test the limits of this generosity in parrots, long considered to be among the brainiest of birds. So they set up an experiment that involved the transfer of treats—with a bit of extra mental gymnastics mixed in.⁠ ⁠ _____⁠ ⁠ After training eight African grey parrots and six blue-headed macaws to barter metal rings for walnuts, the researchers paired the birds up with same-species partners. They then put the parrots in clear chambers joined by a transfer hole and gave one bird—the donor—ten rings, while the other was left with none.⁠ ⁠ Even without the promise of a reward for th...