where available; in drier habitats, moss-like dendroid lichens may be used, or the exterior may be left bare. It is typically attached to a tree branch or to roots and stems under natural overhangs. They are also commonly placed on human-made substrates such as a wire or nail under an eave or in a building. The female incubates the two white eggs for 17 to 19 days and fledging occurs 24 to 26 days after hatch. Vocalization Male blue-throated mountaingems sing two types of songs: a simple "peep song", which sounds like a squeaky wheel lasting about one second, and a quiet but complex "whisper song" lasting as long as eight seconds. The female is also reported to sing during the breeding season to attract the attention of males. The male song differs in several respects from that of oscine birds in that it uses sharp atonal forceful trills and clicks, and has an unusually large vocal range of 1.8 to 30 kHz. Males sing from a perch, usually a bare twig high in a tree. Females vocalize near the nest when alarmed or when disputing a nectar source. The bird also uses ultrasonic vibrations which are not for communication, but possibly serve to flush out and disorient its insect prey. Status The IUCN has assessed the blue-throated mountaingem as being of least concern. It has a very large range and its population of about 2,000,000 mature individuals is believed to be stable. No immediate threats have been identified. The species is highly tolerant of human activity. However, in the northern part of its range it is uncommon and found in only a few narrow canyons, so damage to those areas by fire or human alteration may affect it. Except in the US, little of its range has formal protection. References Further reading Williamson, S. L. 2001. A Field Guide to Hummingbirds of North America (Peterson Field Guide Series). Houghton Mifflin. Co., Boston, MA. External links Blue-throated Hummingbird photo, Article Southeast AZ: Arizona-Sonora Desert Museum Blue-throated Hummingbird photo; photo-2 focusonnature.com Blue-throated Hummingbird photo gallery with picture of nest & egg clutch Lampornis Native birds of the Southwestern United States Birds of Mexico Birds described in 1829 Taxa named by René Lesson Birds of the Sierra Madre Occidental Birds of the Sierra Madre Oriental