The woman made her objections clear as the bird continued to languish.
"I said to her, 'that's not on, it's cruel and distressing to see'.
"And she said, 'yeah, it upsets me as well'." Leaving her shopping in the store, and by this point distraught and crying, the woman took the ailing bird to a nearby vet to be euthanised.
"I just wanted it to be assisted to pass on as quickly as possible. I was very upset ... distraught and crying on the street.
"It's just sad to see an animal suffer."
A self-described animal-lover, the woman suggested the store should invest in traps where birds can be caught before being set free.
Foodstuffs NZ spokeswoman Antoinette Laird said birds loose in supermarkets could spread disease via droppings, "hence the need to remove them".
Asked why traps were not used instead of poison, Laird cited health and safety.
"While our stores endeavour to use the quickest and most humane solutions available for pest control, we also have to look out for the safety of our team.
"Traps in lofty ceiling spots are potentially difficult and dangerous to manage."
However, Laird said the Hillside Rd store had advised it was "looking into alternatives".
She would not be drawn on the type of poison employed.