Mockingbird Spits Up 2 Seeds!

I found this Northern Mockingbird (Mimus polyglottos) on my daily walk to our neighborhood pond in West Sacramento, CA, USA on 13 March 2024. Since he was so close to me and didn’t fly away, I thought I’d take advantage of my good luck and film him. I’m glad I did.
During the 3.5 minutes that I filmed him, he spit up two seeds! I have never seen a mockingbird to that, so I did some research. They don’t spit up pellets like owls do. Mockingbirds reportedly spit up seeds to feed chicks. But that’s not what this mockingbird was doing.
I found two other videos where a mockingbird was spitting up a seed, or an object that looked like one. But I haven’t found a reputable citation that documents why they do this. I didn’t see information about this in Birds of the World, the Cornell’s Lab of Ornithology website.
Do you know why mockingbirds spit up seeds? Are some seed indigestible and better able to pass through the throat than the gut?
/ @frankseverson

[@Fortheloveofbirds2020]

Wonderful observation! You have a very nice channel, I am enjoying watching your videos!