Can I harvest these brassica seeds early and dry them under cover?

I've got some various mustard greens that I'm saving for seed. They are nearing maturity; the pods are starting to dry and all the plants' leaves have dried up. As fast as the pods dry, however, the birds eat all the seeds. Can I cut the plants now and store them under cover to finish drying?

They don't look quite ready enough to me. The pods need to be turning brown and dry, with at least some of them rattling.

If I were you I'd put something like an old pillow-case over them and tie it at the bottom so the birds can't reach the seed pods and any seeds that fall will be caught in the bag. Then as soon as the pods start to rattle and seeds fall out, uproot the whole lot, turn it upside-down, move it indoors and store for a while longer.

Since it's a big plant and the seeds are maturing all at once, I would check to find the pods that are already brown and dry and save those seeds. The first flush of seeds tend to be bigger of better quality and this way they won't get mixed up with other small or immature seeds. Usually a few pods would yield enough for next year's garden. Save the rest of bulk seeds for sprouts or cover crop.

Yes. The plants have already started drying down. Just give them plenty of air-flow. Perhaps rotate the pile every day to help them dry evenly.

As soon as the seed pods on anything start getting leathery, I figure the seeds are mature. Your plants are even turning yellow, so they're ready to go.

I've chopped off side branches full of pods greener than those and ended up with volunteers all over the place.

Thanks for the advice, everyone!

I'd like to note that if you do this, the germination may be splotchy.

But yeah. They should be fine.