My daughter is a senior at Bowdoin and double majoring in Bio/Visual Art with Japanese language minor. She applied applied ED1 but was deferred to ED2. She got in ED2. Later we learned that ED1 is mostly for athletes. Being a small school but still needing to fill many sports teams, it helps the coaches know which athletes are committing to their program. Assuming your son is not an athlete recruit, I would highly suggest applying to ED2 if ED1 is a deferral. However, I suggest you apply ED1 even though it’s unlikely they will accept a non-athlete international student in this pool. It still lets them know Bowdoin was your son’s top choice and willing to commit if accepted.
Bowdoin is particularly strong in environmental Bio. They have an entire separate small campus right on the coast for environmental science studies and research. There isn’t the same opportunity for molecular bio that you might find at a larger research University, however, this can be supplemented by summer research internships off campus. Bowdoin is excellent at helping and placing students in good programs in their desired fields of study.
I don’t know enough about Amherst to compare it to Bowdoin but my understanding is that they are similar type schools. Good luck to your son!