As Posted on the Birdlife South Africa Facebook Group
Aperture was f/5.6 on a Crop / APS-C body at 400mm focal length. With a full frame body at the same focal length the noise level would probably be a stop or so better.
It is recommended with Auto ISO (in low light) to bring the shutter speed (for in-flight birds) down to 1/1000s to 1/4000s. I never go less than 1/2500 / 1/3200s - and sometimes use 1/4000s in very good light (with Auto-ISO).
Best is to experiment quite a bit before jumping to conclusions that you need to upgrade body and / or lens for low light shooting.
Bird in Flight: Yellow-billed duck at Woodbridge Island, Cape Town
Yellow-Billed Duck in Flight : Birds in Flight Photography and Auto ISO |
Source / more camera and Autofocus detail View
Canon Photography Training Milnerton Woodbridge Island | Kirstenbosch Cape Town | Around the Cape Peninsula