Maybe looking for camera footage of possible smoke in cabin. I read from several sources that can happen from burning bird corpse, either in main cabin or the cockpit.
“burning bird corpse smoke.” I never thought about that before, but it might make sense because cabin air is taken from the engine low or high stage engine compressor sections. Low stage air is used during high power setting operation, and high stage air is used during descent and other low power setting operations.
Bleed air for use throughout the aircraft will be up to 500 F. That temperature could roast bird parts, but probably isn’t high enough to make bird corpse smoke.
The pulverized bird flesh and guts would go past the bleed air ports in milliseconds.
Maybe they want to see if passengers commented on the odor?
Probably more likely they are looking for evidence of terrorist behavior.