Elf Owl

It is the smallest owl species in the world, measuring only about 12 to 14 centimetres from head to tail and weighing around 40 grams, comparable to a house sparrow or a large hummingbird rather than to the image most people have of an owl. By contrast, a great horned owl, common across much of the same region, can weigh 40 to 50 times as much. Even other small owls, such as the pygmy owls and screech owls it sometimes shares habitat with, are noticeably larger, making the elf owl an easy size comparison once you know what to look for, though its small size and nocturnal habits also make it very easy to overlook entirely.

The elf owl cannot excavate its own nest cavity, so like many secondary cavity-nesting birds it depends entirely on holes made by other species, most famously the holes that Gila woodpeckers and gilded flickers carve into the trunks and arms of giant saguaro cacti in the Sonoran Desert. A woodpecker excavates a fresh cavity most years, and the wound heals into a hardened, callused chamber called a "boot" that remains usable for a long time after the woodpecker moves on, giving elf owls, along with several other desert species, a ready supply of safe, insulated nesting sites in an environment with very few large trees. Outside true saguaro desert, elf owls use similar woodpecker holes in oaks, sycamores, and other trees in canyon woodland.

Its call is surprisingly loud and distinctive for such a tiny bird, typically described as a rapid, chattering series of high yipping or barking notes, often likened to the sound of a small puppy yelping, given mainly after dark. Males call to establish and defend a territory around a nest cavity and to attract a mate, and pairs and family groups may give a range of related chattering and whining calls. Because elf owls are so small and well camouflaged, and are active only at night, the voice is often the only practical way to detect their presence, and birders in the Southwest frequently locate them by ear near likely saguaro or woodland habitat around dusk.

It is currently listed as Least Concern because it remains reasonably common and widespread across a large range in the southwestern United States and Mexico. However, populations at the northern edge of its range have declined and it has disappeared from some historically occupied areas, particularly where saguaro cacti have been damaged or removed, where large old trees with woodpecker cavities have been cleared, and where desert and canyon habitat has been converted to agriculture or development. Because the species depends completely on cavities made by other birds, the health of woodpecker populations and the availability of old saguaros and large trees are directly tied to how many elf owls a given area can support.