The California gnatcatcher is an insectivorous species. It feeds on arthropods gleaned from California sagebrush Artemisia californica and flat-topped buckwheat Eriogonum fasciculatum. Gnatcatchers require large patches of coastal sage scrub. Tattersall (1988) noted that gnatcatchers preferred coastal sage scrub that had been burned eight or nine years previously. Atwoo's (1990) observation is that gnatcatchers avoid dense and/or tall stands of coastal sage scrub.
The California gnatcatcher utilizes a variety of coastal sage scrub plant species with structural characteristics that will support a nest (Mock, 1993). Most nests are constructed less than 1m off the ground. The California gnatcatcher maintains a year-round territory within a home range during the breeding session (Mock, 1993). Mock (1993) also noted that territories are frequently defined by landscape features such as ridge lines, trails, and breaks in plant communities. Breeding home ranges varied from 2 - 20ha and winter home ranges may expand by an estimated 70%. These ranges tend to be smaller near the coast and larger in the drier, sparser inland areas.
The existing stands of potential California gnatcatcher habitat are in southern Orange Country and on Camp Pendleton, as shown in figure 67. The concentrations are located in coastal zone and foothills areas on Camp Pendleton, which are managed for military training, and Orange County in areas that are being considered for protection under several conservation plans. Plans Build-Out, shown in figure 68 threatens about half of the present 300,000ha.