Lens Upgrade Advice for Canon R7 Bird Photography

Hi! I started bird photography a little over a year ago, and I’m really enjoying it. However, I often find it difficult to photograph birds that are far away. I’m thinking about investing in a new lens in the near future and was wondering if anyone has some recommendations for me :).

My current setup is a Canon R7 with a Sigma 150–600mm EF lens, using the Canon EF–EOS R adapter.