How does 12,800 iso look so good in dull miserable light? I try on a Jay in flight

The weather in the U.K. gets worse and makes photography difficult. I try photographing Jays in flight at 12,800 iso which gave me a shutter speed of 2500th at f4.5 using the OM-1 mk2 The result is amazing. I process the files in DxO Pureraw which I use on all my images, even the lower iso ones. I also show some slow motion footage of noisy Jackdaws. A species I like becuase they are very gregarius and interact with each other a lot. Mike Lane wildlife photography https://www.nature-photography.co.uk/ Music credited to Soundstripe Reprivel Adventurous spirit World cafe Code: VGATCH7SVQK7HQXV, 5J8D5UEEE1DS1BOJ, 5ACYFSH6AZ8IZXJT