Currently recognized as the sole representative of the Old World babbler, or Timaliidae, family in North America, the Wrentit is limited in distribution to the west coast of North America, bounded to the north by the Columbia River, south by the deserts of Baja California, and inland by the Sierra Nevada and Cascade Mountain Ranges.
This long-lived, year-round resident is abundant in cismontane shrublands, particularly coastal scrub and chaparral. It is common in habitat with adequate shrub cover, including second growth, old growth, riparian forests and scrub, valley oak woodland, suburban yards, and urban parks. The Wrentit has been described as the most sedentary species in North America ( Johnson 1972c ), with an average natal-dispersal distance of about 400 meters. Pairs are highly faithful to territories and remain in the same vicinity for up to 12 years.
Wrentits form tight monogamous pair bonds, which are normally lifelong. Both sexes defend the territory throughout the year with distinctive songs that have been aptly called "the voice of the chaparral." The male habitually shares in incubation and is normally in vocal contact at all times with the female, and the pair is even known to roost together, forming contiguous "feather-balls," and to mutually preen. The young commonly remain in family flocks for at least 30 days after fledging and, on occasion, use their natal territory for breeding.
With few exceptions, most of our current knowledge on the behavior, life history, breeding ecology, and population demography of the Wrentit has come from 2 studies, both in the San Francisco Bay region of California. Most of our knowledge of Wrentit life-history originated from Mary M. Erickson ( Erickson 1938 ), under the guidance of Professor Joseph Grinnell, in an intensive 4-year study in a chaparral canyon in Berkeley, California. Her insightful and highly detailed study, summarized in her 332-page monograph, followed, year-round, the life history of 21 territorial pairs and individuals. In an ongoing study at the Palomarin Field Station of the Point Reyes Bird Observatory (PRBO) in coastal Marin County, California, up to 67 pairs have been followed annually since 1979 in coastal scrub, with more than 4,685 individuals uniquely color-banded and more than 1,087 nests monitored ( Geupel and DeSante 1990 , Geupel 1993 ).