Elf owls usually choose abandoned, north-facing woodpecker cavities in saguaro cacti, sycamores, cottonwoods, and other hardwood trees, to raise their young. While some cavity nesters utilize vegetation as nesting substrate, elf owls have been observed removing this vegetation and prefer a bare cavity. Three eggs is a very common clutch size but females can lay anywhere from one to five eggs in spring: late March to early May. The eggs are usually round or oval shaped with a white coloration and are from 26.8 x 23.2 to 29.9 x 25.0 mm in size. The eggs are incubated for about 3 weeks before the chicks hatch. The young owlets fledge at about 10 weeks. Usually, chicks are born in mid-June or early July. By the end of July, they are almost always fledged and ready to set out on their own.
They are often found in chaparral, and are easily found during their breeding season. During dusk and just before dawn are the times this owl is most active, however, hunting is performed mostly during nocturnal hours. Straight line flight is often deployed for this purpose but they will use an arced flight when in the vicinity of the nest and for flying to and from perches. They live in cacti much like some birds, using the shade and climate the cacti provide.
Elf owls usually are not aggressive and feign death in any dangerous situation, especially when a threatening animal comes inside their saguaro. Territories are established by the male and are defended by both the male and the female. This is done through the use of song. During the breeding season Elf Owls are monogamous and stay in breeding pairs, but can be found in small groups during migration and when mobbing predators. Adults as well as young can be subject to predation by other owls, hawks, and certain jays.
The Elf Owl migrates to the southwest United States; California, Arizona, New Mexico, and Texas, in the spring and summer for breeding. In the winter, it is found in central and southern Mexico. Migrant elf owls return north in mid-April to early May. Resident populations occur in a couple of places in south central Mexico and along the Baja peninsula.
Elf owls feed mainly on insects, so they occupy habitats with a ready supply of them. Agaves and ocotillos are ideal places for foraging, as moths and other insects may be found in their flowers. In urban areas they can be seen utilizing outdoor lights that attract bugs as areas for insect hunting. They are often seen chasing after flying insects, with a flight similar to a tyrant flycatcher's. They also feed on scorpions. Once the owl has killed the scorpion, they can be observed removing the stinger before consumption. The elf owls seem to not be bothered by the scorpion's stings. They feed primarily on invertebrates such as moths, crickets, scorpions, centipedes, and beetle. They will also feed on small mammals and reptiles.