The Te Awamutu Warehouse carpark was a sparrow graveyard after the birds were believed to have been poisoned.
Bodies of dead sparrows lay scattered as far as ASB Bank and the Courier office.
Members of the public discovered the dead sparrows underneath two large oak trees in the carpark - the sparrows' usual roosting spot.
Te Awamutu woman Lee-Anne McKee suspects someone poisoned the sparrows because they were sick of bird poo on their car.
"If you park your car under the oak trees then it will get covered in bird poo.
"But too bad, the trees are the homes of the sparrows.
"Park somewhere else."
McKee says the act is "heinous".
"It's just sad and revolting to see something like this happen."
A Waipa District Council worker began to collect buckets full of dead sparrows on Wednesday afternoon.
He said it looked like at least 50 birds were dead.
"At this stage we do not know what caused the birds to die," Waipa District Council senior communications advisor Nicole Nooyen said.
"We're talking with other agencies to see if further investigation is needed."