Although steroids are widely known to affect behavior through activation of nuclear/cytosolic receptors ("genomic" effects), steroids can also rapidly affect behavior via modulation of signal transduction pathways ("nongenomic," fast actions, or rapid effects). In zebra finches, there is evidence that sex steroids have context-specific effects on pair-maintenance behavior, on both acute and chronic timescales. Here, we quantified the effects of orally administered testosterone and 17β-estradiol (E2) on pair-maintenance behavior. We show that E2 rapidly affects female, but not male, affiliative behavior profiles during a partner separation and reunion paradigm. More specifically, E2 rapidly (within 5-15 min of administration) increased females' spatial proximity to a partner. This effect was present regardless of breeding condition (water restriction or water ad libitum). Combined, these results contribute to a growing body of evidence implicating sex steroids in the regulation of prosocial behavior. (PsycINFO Database Record (c) 2018 APA, all rights reserved).