Most likely not. I think the compost would be angry that the 'good' part of the seed has been eaten, and then refuse to eat the shell. Sunflower seeds are about as hard to compost as plastic grocery bags. That's why the birds don't eat the shells.

However, give it a try and I bet they disappear in no time.

Yes. They may not compost readily in the compost pile but they will deteriorate slowly even when add to the soil. This type of material is more attractive to fungii than to bacteria.

They will break down but it'll take a while.

I go through a 20kg bag every month in the winter, come spring there is a pile of shells sitting under the feeders. I just rake them around a bit and leave them there but my feeders are sort of out of the way so I don't care. (Laziness breeds efficiency)

Lloyd

Sunflower seed hulls are supposed to be allelopathic, according to many reports, however, the only time I have seem a problem is when they are deep enough, thick enough, to prevent sunlight from reaching the soil under them. Sunflower seed hulls are organic matter and can be composted just like most other organic matter but they might be difficult for the bacteria to digest just like woody material is. I've not picked them up and composted them just mulch mowed them into the soil where the grass grows greener, thicker, faster than in areas outside where those hulls have been mulch mowed.

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I'll sweep up the spent bird seed hulls, including sunflower seeds, and compost it. It's a slow go though. I don't mind. The greater the diversity that goes in, comes out.

to sense
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Yes, dump them in the compost, they'll be gone super fast!