Agreeing with the previous points on native glass.

• Canon RF 600mm f/11 IS STM is a reliable, budget-friendly alternative
• It offers massive reach for birds
• Sticking with RF avoids potential adapter lag.

Coming back to this... I spent a solid decade chasing birds with different bodies before landing on mirrorless, and honestly, the R7 is a beast for wildlife because of that crop factor. I remember my first trip out with a full frame and a 400mm lens; I was so frustrated because the birds still looked like tiny specks in the frame. Then I switched to a crop sensor like yours and suddenly, that same focal length felt like a sniper rifle. Basically, because your sensor is smaller, it crops the image. In technical terms, a 400mm lens behaves like a 640mm on your camera. That is a massive advantage for backyard stuff where you cant always get close. If you ever feel like experimenting with older glass, you could grab a Canon Mount Adapter EF-EOS R and look for a used Canon EF 70-300mm f/4-5.6 IS II USM, but sticking with the RF mount is usually smoother for autofocus. A few quick tips from my time in the field:

• Keep your shutter speed way higher than you think. Even if the bird is sitting still, its head is twitching constantly. I try to stay above 1/1000s or even 1/2000s if there is enough light.
• Use the electronic shutter on that R7 to avoid shutter shock, which can blur your shots at certain speeds. I once spent four hours shivering in a bush trying to get a specific hawk shot only to realize my shutter was at 1/200 and every single photo was blurry... dont be like me lol.

Honestly i have been shooting with that exact setup for ages and it works well for me. No complaints at all. For your budget, the Canon RF 100-400mm f/5.6-8 IS USM is the best choice hands down. Heres why I am so satisfied with it:

• Its super light for hiking
• The autofocus is actually really fast
• Fits your budget easily You're gonna have a blast with those birds!