Alfred Russel Wallace (1823–1913) and Carl Benjamin Hermann, Baron von Rosenberg (1817–1888) were naturalists with similar goals in their exploration of the Malay Archipelago. Their collaborations have not been the subject of any previous study. They first met in May 1858 on the coast of Dorey, the northwestern part of New Guinea. Together they discovered two birds new to science, the Dusky Lory Pseudeos fuscata (Blyth, 1858) and the Fairy Lorikeet Charmosynopsis pulchella (G.R. Gray, 1859). Wallace did not propose new names himself, while the Chalcopsitta leucopygialis Rosenberg, 1859 (nomen nudum) and Charmosyna pectoralis Rosenberg, 1862 lost their priority. Wallace visited Aru Island for six months in 1857, where he collected 113 bird species as enumerated in his private notebook, now transcribed in extract for the first time. Wallace's collections from Dorey were examined by George Robert Gray (1808–1872) in 1858 after they were received by the Natural History Museum in London. When Rosenberg was working out the distribution of various birds in the archipelago in 1862, he had not yet visited the Aru Islands. His list of 86 bird species from Aru was contributed by Wallace, most probably during their discussions when they met in Ceram in November or December 1859. The historical narrative provides two rare instances where Wallace's presence was acknowledged by fellow naturalists in the field, and at the same time gives insight in the cooperation and potential scientific rivalry of the period.