Feeding a parrot uses item in off-hand as well

Feeding a parrot (with seeds or cookies) using the main hand will additionally use the item in the off-hand, if any.

To recreate: Put seeds in you mainhand and a cookie in your offhand
Feed a parrot.
The parrot will die and both items will be consumed
It will also work with a cookie in your mainhand and seeds in you offhand, or with seeds in both hands.