Birding in BC Community

I am not very knowledgeable on gulls. Any help in identifying them would be great! They were in Banff, Alberta. My first guess would be ring-billed gulls. My next guess would be Thayer's gulls. Thank you in advance for any help!

https://youtu.be/wqc70vtB64g

Okay, I am now confident they are juvenile ring-bill gulls I will be changing the title and description of the video accordingly...