The Rufous-tailed Hummingbird is known for the male's glittering green throat and coppery tail. It feeds on nectar as well as small insects and spiders.
The male's back and flanks are golden to bronze green, its throat glitters golden green, and its tail has bronze and copper tones.
Young male Rufous-tailed Hummingbirds take time to develop definitive plumage and bill color. Their throat is not yet fully iridescent green, and the upper bill shows less red than in definitive males. Juvenile wing coverts are dull green; young tail feathers have washed-out bronze edges, sometimes broken at the tip. The Belize analysis included N=290, with 81 first-cycle samples.
The preformative molt replaced 0–3 inner greater coverts (mean 0.13). Definitive prebasic molt occurred from April through September and peaked in June–July. The second prebasic molt ran from March through August, with peaks in April–May and July. Among definitive-cycle basic birds, bill corrugations were usually absent; 2.67% retained corrugations on up to 10% of bill length.
An extinction-risk assessment has not been added yet.