Steps to Reproduce:
Go to Creative. (optional)
Break a Bee Nest filled with Bees. If you are in Creative, just do it. If you're in Survival, do it with Silk Touch.
Break it once again with the steps above.
Observed Results:
Bee Nests appear as an individual item in your inventory.
Expected Results:
Bee Nests stack.
This is a feature request. This site is for bug reports.
Note that, if bee nests with bees stacked they would have to lose any unique data such as the hp of the bees and how long they had been in the nest.