A passenger on the Air New Zealand flight which left Dunedin Airport at 7.10am for Wellington said passengers smelled burning bird after takeoff.
The pilot told passengers he saw the birds, but the only evidence of the bird strike was the smell of the bird being cooked by the engine.
The passenger said it smelled like "grandma had burnt the Christmas turkey".
He said it appeared passengers were confused rather than alarmed, though noted landing in Christchurch interrupted travel plans and resulted in lengthy delays.
An Air New Zealand spokeswoman confirmed flight NZ680 from Dunedin to Wellington was diverted to Christchurch following the bird strike.
There was an aircraft change in Christchurch before the flight continued to Wellington.
Bird strikes were not uncommon, she said.
Aircraft were designed with that in mind and pilots were trained to respond to the scenario.