Rural/Farm Life

And when a hen goes broody they look spacey, make unusual sounds (almost like they are talking with the eggs) and are pretty insistent on staying put and will become very agitated if you try and move them.

As for the adding eggs to the nest issue, the hen will, more often than not, stay put on the eggs preventing other hens from adding. One potential problem can occur if you allow another clutch of eggs to accumulate the hen can become "confused" on her short breaks away from the nest and choose the wrong pile when resetting. It is best to remove other eggs regularly, or better separate your broody hens. The wisdom of separation becomes even more apparent as the chicks begin to arrive. Other hens can be quite nasty to chicks they are not nesting.

I found the best way to encourage them to set was to leave a small pile of eggs in the nest box. It can become confusing when there are new eggs being laid with the waiting eggs and can be hard to keep track of the fresher ones (some people mark the waiting eggs with a permanent marker so they know which to leave and which are fresh) . Some have also suggested using wooden eggs (they are the same ones used to influence an egg laying area and can be switched out if a hen goes broody over them) as a pile but my birds tended to separate out the wooden eggs when they went broody.