https://www.youtube.com/watch?v=fVFBXCfFopM&app=desktop
Watch the top right of the video. What you say is a bird goes from right to left very fast, not a bird at all.
It’s a telephoto lens so anything moving in the foreground is going to appear to be moving faster. Here’s the entire video that you can step through or play in slow motion. Other birds or insects can be seen flying around before the explosion.
http://anilyzer.com/?page_id=7&type=youtube&vId=_BgJEXQkjNQ#playbackRate=1&seekTo=0