Introduction

Verdins are active, insectivorous passerines that inhabit desert regions of the southwestern U.S. and northern Mexico. Among the smallest of North American songbirds, Verdins are nevertheless conspicuous because of their loud and persistent calls and their prolific nest-building behavior. They forage almost continuously, especially in cool weather, by gleaning live foliage and flowers for spiders and small insects. Verdins are found wherever thorny scrub vegetation is present and prefer to nest in acacias (Acacia spp.), paloverde (Cercidium spp.), smoke tree (Dalea spinosa), mesquite (Prosopis spp.), or desert lavender (Hyptis emoryi). They are not known to migrate; most juveniles disperse in their first winter up to several kilometers from their natal territory.

The conspicuous nest of this species is a complex construction of protective thorny twigs, grasses, leaves, and feathers (see Fig. 5). Spherical or ovoid and 15–25 cm in diameter, these enclosed nests are placed in the outer foliage of a shrub or small tree. The usual opening is to one side at the bottom of the nest, 3 cm wide and with a small platform of twigs. Smaller nests are used for roosting throughout the year. Roosting nests are built at any time of year and maintained continually by the addition of insulating grasses and feathers. Old nest materials are recycled, and they may be stolen from other Verdins.

Verdins are the only New World representatives of the Remizidae, a family that includes the penduline tits of Eurasia (Remiz) and Africa (Anthoscopus). The relationship of the Verdin to these Old World taxa has been controversial and only recently more firmly established (Sheldon and Gill 1996).

Significant research has revealed much about the breeding biology, systematic relationships, and physiological ecology of this species (Taylor 1971, Webster and Weathers 1990, Sheldon and Gill 1996, Wolf and Walsberg 1996a). Many questions remain, however, regarding Verdin behavior, vocalizations, and geographic variation. The Verdin’s tractability, ease of capture and manipulation, and open habitat make this species an exceptional subject for continuing study.