We have had a couple of other inquiries this spring as to this insect and have entomologists investigating what they might be. Cocoons are more likely than eggs, but there are too small to analyse thoroughly via photos and we are waiting for a sample from another site to produce an ID. You can try to gently tweeze or scrape off a few intact-looking individuals and put them into a sealed container; we are hoping an adult insect will emerge from them soon (especially since a few already look opened) which would be much easier to identify. (You mentioned some being on twigs, so these would be easier to collect and bag without risk of damaging the insect inside.)

They are probably harmless, but we are as curious as you about their identity. If you experiment with trying to hatch some out, please follow-up with any photos you can take.

Miri

Thank you for the response. I bagged up a few sticks. Will being in a ziploc bag kill them before they hatch/emerge? 

You're welcome.
Probably not, as oxygen use by insects is low enough that for the amount of time they'd probably need in the bag, they'll have enough. Leave the bag filled with air, though.

Miri