Something I haven't see or heared of before

Luciano's #1 Bride, Siena, decided to build her nest, in one of those grapevine balls. From the start, one of my littke Yellow headed Star girls, has been lending her a hand with the construction. Since Siena, laid her egg, the little Star hen has been helping her sit on the eggs. The take turns sitting on the eggs, and quite often sit together.
I have never heared of something like this, other than with Societies or Zebras. Has anybody else ever come across a similar incident?
Now, I didn't go rummaging in the nest, to see if there are Star eggs, but I know there are Canary eggs. So what gives???

~Elana~