Great White Egret.

Great White Egrets have been resident at Llangors Lake in the Brecon Beacons for a few years and hopefully breeding is on the horizon. They remain, however, as do all Herons and Egrets painfully shy, and you usually have to take them by surprise to get near them. I was walking back from the bird hide there, where I had basically seen very little, when this bird took off and flew across me for about five seconds. I was carrying my Canon R5 with the RF100-500 f7.1 and the RF 1.4 TC attached - my standard combo these days, but even with the 1.4 TC attached and at 1120mm the camera locked onto the bird’s eye immediately.
This combo is very effective for walking around photography.