>Did you read the article? [...] , but learning clearly is an essential factor.
I think your reading of the article missed the point of their experiments that dissected the learning :
Yes, the "learning from other-species foster parents" was affecting their non-cowbird type of behavior (e.g. songs).
But no, they did not "learn" the cowbird-specific behavior from any parents. E.g. They figured out their preferred roosting in the fields at age ~20 days on their own.
I think your reading of the article missed the point of their experiments that dissected the learning :
Yes, the "learning from other-species foster parents" was affecting their non-cowbird type of behavior (e.g. songs).
But no, they did not "learn" the cowbird-specific behavior from any parents. E.g. They figured out their preferred roosting in the fields at age ~20 days on their own.