In 1922 Frank M. Chapman hired a family of Ecuadorians to collect birds and mammals for the American Museum of Natural History (AMNH). In the following two years, Carlos Olalla and his four sons (especially Alfonso and Ramón) shipped some 3500 carefully prepared and neatly labeled specimens of Ecuadorian birds to New York. In 1925, under a new contract with the AMNH, the Olallas moved their operations to northeastern Peru, and during the next two and a half years, mostly as a result of efforts by Alfonso and Ramón, they sent over 7000 specimens of birds to New York from Amazonian Peru, as well as additional thousands of specimens of mammals. The two brothers shifted their operations to Brazil in 1928. Alfonso went on to ship even larger collections of birds from Brazil to museums in the United States, Sweden, and Brazil. Altogether these collections have provided the documentation for much of what we now know about the distributions of Amazonian birds and mammals.

In 1962 accusations surfaced that the Olallas had falsified much of the information about their specimens. Although based on hearsay, these accusations raised lingering doubts about the Olallas' collections. Alfonso sent reports of the brothers' activities to the AMNH with their shipments of specimens. These reports together with their correspondence with Chapman and other curators are still preserved in the archives of the departments of ornithology and mammalogy. Examination of these archives and of most of the Olallas' specimens of birds and primates from Peru provides a clear view of their activities for the first time.

All of the Olallas' collecting sites in Amazonian Peru can now be confidently located, and a large majority of their specimens from these localities accord with current understanding of avian distributions in Amazonian Peru. The accusations of general carelessness or systematic duplicity can thus be rejected. Nevertheless, there remains a small number of problematic specimens. Especially suspect are those acquired from the Olallas in Iquitos by Harvey Bassler with labels from the mouth of the Río Urubamba. These specimens eventually came to the AMNH as a part of Bassler's collection, rather than directly from the Olallas.

Alfonso and Ramón Olalla's choice of collecting sites suggests that they became aware of the importance of major rivers in limiting avian distributions in Amazonia, and their correspondence with Chapman suggests that their collections brought this insight to the attention of ornithologists in New York. In addition, their collections suggest patterns of avian distribution that still need further investigation, especially the extension of some species of the Andean foothills into the lowlands of upper Amazonia and the less consistent limitations of avian distributions by the upper Río Ucayali in comparison to the Río Amazonas. No doubt some of the Olallas' specimens indicate yet undiscovered features of avian distribution in upper Amazonia, where, despite Alfonso and Ramón's pioneering efforts, there is surely more to learn.