I had trouble fiinding the page for submitting comments. I called Regulations.gov and the agent helped me find the page. Here's how to do it:
1) Click on the link Kathanne gave: https://sen.gov/6LLJ.
2) Click on the "Regulations.gov" in the top left-hand corner of the blue banner at the top of the page.
3) Scroll through the "What's Trending" boxes until you find the one about the Migratory Bird Act and click on that box.
4) That will take you to a page with "request for public comment" in the title.
5) Below the title, on the left-hand end, there is a blue box that says "Comment." Click on that.
6) That takes you to the comment form
Comments will be accepted up to midnight Eastern Time today, March 1st..
Hope this is helpful for others like me!