Puertorican parrots eating west indian tree fern stems

The Puerto Rican parrot (Amazona vittata) is known to eat the leaves, fruits or seeds of more than forty species of plants.  In the Rio Abajo forest the parrots sometimes consume the stems of the fronds of the tree ferns of the genus Cyathea.   The effect of the parrots’ activity is to completely defoliate the ferns.  The parrots consume all stems, from very young ones that are starting to unfurl to the oldest ones.    The ferns eventually produce new leaves and recuperate fully from the parrots foraging activities.    The birds don’t eat the whole frond, just parts of the stems.    I find the fact that the parrots were using the tree fern stems as food remarkable given that the birds that have been  released into the wild since the reintroduction program began were given a wide variety of wild leaves, fruits and seeds before the release, but not tree fern fronds.