Elf OwlMicrathene whitneyi Elf Owls are most vocal on moonlit nights, especially when setting up territories. Their calls are quite different from the sounds of other owls and have sometimes been described as puppylike barks or elfin shrieks and laughter. Males give a multinote chatter song to advertise their presence at nest cavities. The quality of this song varies from soothing to manicits intensity possibly keyed to the reactions of potential mates or competitors. Once pairs are formed, partners keep in contact with each other around nests with soft descending peew calls. The birds also have an alarm calla sharp yip given singly or in a series and often in response to disturbance. Sometimes they give yips to sounds such as a slamming screen door or a barking dog, or to the menacing silhouette of a larger owl. Both males and females give yips, and the owls are always alert to intruders in the early breeding season, responding no matter whether the intruder is another Elf Owl, a potential mammalian predator, or a human playing a tape or giving a whistled imitation of the owl. They react especially strongly to other owls in their territories, both with alarm calls and mobbing behavior. For more than a decade Elf Owls have nested in our backyard in rural southeastern Arizona. In 2003 and 2004 they used a wooden nest box that we had mounted fifteen feet up on the limb of a sycamore and had fitted with a removable back. Once the chicks were large enough to no longer need brooding, we replaced the back with a glass plate during nighttime observation periods so that we could watch feedings inside the box from an outside blind erected atop scaffolding. The adults and youngsters exhibited no problems in accepting temporary insertion of the glass plate in the nest box, and it became possible to study directly how the parents distributed food among their nestlings and how the nestlings interacted with one another. With the success of these observations, we modified the nest box even further in 2005, fitting it with a tiny infrared spy cam and microphone and leaving the wooden back permanently in place. With this arrangement, we were able to watch an entire breeding cycle inside the box via a cable television hookup to our living room, tracking and recording activities day and night from a camera viewpoint inside the box that looked down at the nest bottom from above the box entrance.