I've had the Canon EF 100-400mm f/4.5-5.6L IS II USM lens for a couple of years now, and it's my favorite lens. Canon has recently introduced an RF version improvement of this lens in the form of a 100-500mm f/f/4.5-7.1 L IS USM lens.
In this video from Mark Smith, he gives his first impressions of both the Canon R5 and the new 100-500mm lens. The R5 is an excellent camera featuring a 45-megapixel sensor, and when paired with the RF 100-500mm lens, I'm sure it will be incredible.
Bird photography can be challenging, presenting many situations that make accurate focus difficult. Mark points out a few of these situations in this video. Mark's extraordinary storytelling abilities make this first impression video not only informative but also entertaining.
A close friend of mine recently picked up the Canon R5, and the images he has captured look fantastic. I really do believe that the Canon R5 is one of the biggest leaps in technology that Canon has produced in quite a few years.
I'm hoping to purchase the Canon R5 soon, and I really do think it's going to be my workhorse for years to come. As for the lens, I'm probably going to shoot my 100-400mm lens for a while, as the 100-500mm is a bit on the expensive side.