The first postcard is found between pages 112-113, dated April 12. Eric Husch begins using the idea of birdwatching as a metaphor for his search for F.X. Caldeira. The post script advises the reader to destroy the postcard after reading.
The second postcard is found between pages 178-179, dated April 15. Eric Husch has made progress in his research, saying, “People here say they saw the nightingale, but don't remember specifics, not even where she nested.” Eric Husch's bird watching code indicates that he has found people who know of F.X. Caldeira and he is getting closer to finding her.
The fourth postcard is found between pages 192-193, dated April 19. Eric Husch has found a family who know of a “very old nightingale” and say that people are protective of her. They believe Eric Husch has good intentions with his book and offer to take him to see the old nightingale the next day.