A pilot was killed and his aircraft destroyed when it crashed into the ground at a property near Chinchilla, west of Brisbane, on September 19.
The aircraft hit the ground with the fuselage "in a near vertical attitude" and its "propeller and engine buried in the soft earth", the Australian Transport Safety Bureau's Stuart Godley said.
"A large bird carcass was found in the cockpit and the bird's wings were located about 300 metres north of the wreckage, in-line with the aircraft's track."
The engine appeared to be delivering power at the time of impact, a preliminary report says.
Examination have shown the bird was an Australian bustard or Plains turkey, which weighs up to eight kilograms and can be as tall as 1.2 metres.
They are mostly ground dwellers, but are capable of flight.
Farmers began their search for the plane at about midday after concerns were raised when the pilot failed to respond to a call about whether they needed more fuel.
One of the local farmers found the aircraft in a paddock where the pilot had been spraying pesticide shortly after.
The field where the accident occurred would generally be sprayed at a height of two metres above the ground, just above the weeds, the aircraft's operator advised.
While birdstrikes causing fatal aircraft accidents are very rare, the ATSB is separately investigating an incident involving a wedge-tailed eagle carcass located near the accident site of a helicopter that experienced an "in-flight break-up" in NSW in July.
The ongoing investigation of the Chinchilla accident will include further examination of electronic components, operational documents and maintenance records.
A final report will be published at a later date.
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