This isn't learned behaviour though. The kites tried eating the invasive snails immediately, but they were too large to be cracked by their beaks, being two to five times larger.

The change to eating the larger non-native snails was facilitated by larger beaks seen in the years after the invasion.

It seems like the local applesnail had a crash due to drought in the early 2000's (partly caused by the draining of wetlands for development), and the invasive island applesnail was first seen in 2004. There are even more species of invasive snail now, but the opportunity likely arose because of a population crash.

The fittest in this case are the kits that can eat the snails they find, not by being less picky, but by having larger beaks.