The Sony RX10 IV is an excellent camera in for filming, macro work and bird photography, but capturing birds in flight (BIFs) is not its strongest suit.
It has great phase detect AF with numerous points, a blazing 24 fps ARW with deep buffer, and a 600 mm (equiv.) lens which is sharp even wide open. However, its EVF stutters after a short burst, causing disorientation to my eyes when acquiring and tracking the moving subject. Worse, its viewfinder is much darker than the OVF of DSLRs (the latter always have the lens wide open during tracking regardless of exposure settings).
Those said, with persistence, the RX10 IV can still catch BIFs, albeit not at the success rate of a DSLR + a good prime, like my Canon 7DII + 400 f/4 DO II. I'd still opt for the latter combo when the birding sortie is primarily intended at BIFs.
The RX10 IV is the best BIF camera when it's the only gear available, especially at times when accidental birding happens and it's conveniently packed in the car's trunk. Also, it's the only BIF rig that I can safely pack in my bike's luggage box when riding (Kit A below, kit B needs a bigger vehicle for carriage).
|Click for the larger image
And here's my birding bike whose top box can easily accommodate the RX10 IV bag, some drinking water and other small stuff.
|Kawasaki Versys X 300, with Givi E19N top box and Oxford M4R tank bag
Shooting info - Sony RX10 MIV, 24 mm equiv., 1/60 sec, f/5.6, ISO 100, manual exposure, fill-in flash (in-camera), near full frame resized to 1500 x 1000.
A good DSLR + a fast focusing prime lens is still the best BIF system on the planet, as long as you have this available when a BIF shooting opportunity materializes.