This dataset includes captures of mainly Grasshopper Sparrows (GRSP) prior to 2017, and after that, additionally many Dickcissels, Eastern Meadowlarks, Brown-headed Cowbirds and other songbirds. Each row pertains to an individual captured on a certain day. Individuals can repeat. Most captures include data on age, sex, head-bill, tarsus, wind chord, molt score, fat score, and mass. In many cases, a single feather was collected from each bird for isotopic analyses.