This data publication contains information collected as part of a field, laboratory, and modeling effort aimed at uncovering ecological drivers of avian malaria transmission and impacts on Hawaiian honeycreepers across an altitudinal gradient on the eastern flank of Mauna Loa and Kilauea volcanoes. Forest bird banding data and blood samples for diagnosis of Plasmodium relictum, the agent responsible for avian malaria in Hawaii, were collected from 2001 - 2005 at nine sites ranging 25 to 1,800 m above sea level. This data file reports morphometric data, age, sex, molt status and diagnostic results for avian malaria from native and non-native forest birds that were captured with mist nets at the nine study sites. Related data describing site and sampling coordinate data, mosquito capture data, mosquito avian malaria infection data, and point-transect distance sampling data is available at https://doi.org/10.5066/P95LVJIC. This XML describes one tabular CSV file: Banding Diagnostics Merge Final.CSV.