The flight instructor reported that, while performing maneuvers about 800′ above the ground, a bird hit the left wing.
He returned to the airport in Phoenix, Arizona, without further incident.
A post-accident examination of the airplane revealed substantial damage to the left wing.
The flight instructor reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.
Probable cause: An in-flight collision with a bird.
NTSB Identification: GAA17CA161
This February 2017 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

Hmmm, I wonder what a nice size drone would do?
A friend of mine was flying low on the Colorado river in the Bullhead, Laughlin area in his Comanche 180 when he startled a mud hen that flew straight up and hit the leading edge of the right wing, the damage that incurred on that leading edge was unbelievable, It was about 8″ to 10″ pushed in, needed to replace the entire wing panel. The leading edge of that airplane is about .025″ thick and is radius , being a very tough part of the wing. He was unaware of the damage until he landed and was very surprised, at what damage that 1 – 2 pound mud hen made. Unbelievable !!
Maybe it was the Piper that hit the bird.