A heretofore unknown population of the endangered Red Siskin (Carduelis cucullata) was discovered in southwestern Guyana, ∼950 km from populations along the Venezuela coastal cordilleras. Most Venezuelan populations have been greatly reduced by the pet trade during the past 150 years, thus the newly discovered Guyana population represents an opportunity to insure the survival of this highly endangered species in the wild. Breeding of Guyanese siskins coincides with both breeding periods (May to early July and November—December) that have been documented in Venezuela. Breeding behavior, vocalizations, feeding habits, and immature plumages are described.