When you put a regular egg (not golden) into the cooking pot it turns into oil

Golden hesperonis eggs can be used to make extrodinary kibble.

They don't lay golden eggs passively, you have to take them out too eat fish so they even have a chance!

Tamed Hesperornis WILL lay golden eggs, just takes a bit of time. I had mine on follow in the Redwoods river, and whistle attack targeted it on a fish. It must kill and harvest SEVERAL fish before going on land to lay an egg. It will either lay a normal duck egg, or it will lay the golden egg. It seems to be random, however mine laid about five normal eggs for every golden egg. If the type and size of fish matters, I have not figured that out yet. It will usually kill all types in one shot, and it will not agro every single sabertooth Salmon in the vicinity when it kills one so don't worry about them ganging up on your duck. I was using a lvl 80, probably tamed around level 50 or so and all I put points in was health. Have it kill every single fish in the river before you give up trying for that golden egg. It will happen, give it time. Hope this helps :)

To get the most polymer, use a club.

If you get a fish basket, you can make a fish farm to mass tame these guys, then get a high level moschops and pump harvesting levels into organic polymer, and boom, you got a organic polymer farm.

Their eggs ( not golden ) make oil instead of kibble when cooked.

We need breeding info on these.

Best way to get eggs from in is whistle it to attack and eat fish and after every 6-7 fish pick it up and throw it on land it will lay an egg works 90% of the time