Until 1997, according to Proudfoot and Beasom, no comprehensive study had been performed to analyze the diet of Ferruginous Pygmy-Owls. They observed owls in Texas, analyzed prey remains, and took video footage from inside nest boxes in order to confirm or clarify anecdotal accounts of Ferruginous feeding habits. Their results indicate that Ferruginous Pygmy-Owls, at least in Texas, are generalist predators and do not depend on any particular species to fill their diet (Proudfoot and Beasom 1997). Analysis of prey remains indicate that their diet consists mainly of mammals (8.6%), other birds (10.5%), reptiles (22.5%), and insects (58%) (Proudfoot and Beasom 1997). They also observed instances of predation on the hispid cotton rat (Sigmodon hispidus) and Eastern Meadowlark (Sturnella magna), confirming anecdotal accounts of the birds taking prey items larger than themselves (Proudfoot and Beasom 1997). Still, Ferruginous Pygmy-Owls have been under observation for a long time, and the feeding habits among owls elsewhere in their distribution is similar (Flesch and Steidl 2010). For example, in Brazil Schubart et al. (1965) reported a variety of insects in the diet (orthopterans, beetles, termites of the genus Nasutitermes, odonates, Hymenoptera: Formicidae, and cicadas) as well as a rodent and small reptiles (several lizards, including a geckonid, Gymnodactyulus; and a snake). Among insects, the most common prey items are grasshoppers and crickets in the US, and also some scorpions in Mexico (Flesch and Steidl 2010; Proudfoot and Johnson 2000).
Peak feeding occurs during the dawn and dusk. During the nesting season, owls forage mainly between 6:00 and 9:00, and between 20:00 and 22:00 (Proudfoot and Beasom 1997). Ears are symmetrical, which suggests that vision plays a more important role in the location and capture of prey items (Proudfoot and Johnson 2000). Ferruginous Pygmy-Owls perch at low heights and use short, swooping dives to catch prey once it has been found. Although adults capture prey in their talons, juveniles sometimes attempt to use their beaks. Killing prey usually consists of biting behind the neck to sever the spinal cord. Before consumption, many mammalian, avian, and insect species are decapitated. Avian species are also sometimes plucked, and their wings and tails are usually removed. Insects are often dissected to expose their softer parts; exoskeletons and other hard body parts are discarded. Smaller prey items (mostly insects) are consumed immediately upon capture, while larger prey may be cached for later consumption (Proudfoot and Johnson 2000). Proudfoot and Beasom (1997) observed owls in Texas using open cavities and patches of ball moss near their nests to store prey. Pellets are 19-25 mm and defecation occurs at habitual posts near nesting sites (Proudfoot and Johnson 2000).