I've not been in Costa Rica, I wish, but have spent a few weeks in Guatemala.
I was more afraid of the giant cockroach in the bathroom of the convent we stayed at.
I have been in the jungle, so called, but not hiked it, pampered tourists that we were, elementary vintage plane to get to Tikal, puff puff. We did get to be friends with the archeology tour guide at Tikal, who had hiked and thumbed from Rio to there, a brit who married a native..wonder how she is now.
I don't remember birds all over the place, but do remember the bird songs.
How to advise your friend, I don't know, but I don't remember any attacking birds.