Abstract
Interspecific alloparental care is a little-known behavior among Neotropical birds. Here, we describe the first case in South America involving hummingbirds (Trochilidae). In an urban area of São Paulo, Brazil, we observed an individual of Eupetomena macroura (Swallow-tailed Hummingbird) caring for the chicks of Chlorostilbon lucidus (Glittering-bellied Emerald). The observations were made during the months of August and September 2024. We first recorded a Swallow-tailed Hummingbird carrying nesting material to a Glittering-bellied Emerald nest (before hatching). After the two youngs hatched, we recorded Swallow-tailed Hummingbird feeding the chicks ( n = 10 events). This type of behavior has been thought to be related to various factors, including the loss of nest and/or chicks. There is the possibility that the constant defense of territory, practiced by some species of hummingbirds (e.g., Swallow-tailed Hummingbird), may also have influenced alloparental care and nest appropriation. We suggest that this type of relationship should receive more attention in behavioral studies of hummingbirds.