Good question @luzsa2004! This would depend on several factors such as motion zones, motion sensitivity, camera angle, and proximity of object. As this bird looks to be close to the Cam, and your Cam is angled to only cover the entryway, it is expected for it to trigger motion detection.
If you are wanting to avoid detecting objects or animals, I recommend trying the People Only Mode setting in the Ring app. This will help to only alert you of human like activity. I hope this helps!
Like my answer? Accept it as a solution (click on the 'Accepted Solution' button next to reply). Learn more about the Community, here.