Zooming with a spyglass then switching to a bow shows for a split second the arrow- shooting animation in your hotbar.

Steps to reproduce

1. Have spyglass and a bow in your inventory
2. Zoom using the spyglass
3. While still being zoomed in switch to your bow using your mouse's scroller

It is for a very split second, probably one frame you may not see it in the video but you can try it for yourself.