The Bridled Titmouse is well named for its striking facial pattern, which in combination with a crest distinguishes it from all other North American species of titmice and chickadees. Originally described by Charles Bonaparte, the species was named for Wollweber, who supposedly collected a specimen in Mexico before 1850; Wollweber's role remains mysterious, however, because museum archives lack any information concerning him ( Mearns and Mearns 1992a ).
The Bridled Titmouse and the Mexican Chickadee (Poecile sclateri) are the southernmost members of the family Paridae in North America. Primarily a broadly distributed montane Mexican species, the Bridled Titmouse is restricted in the United States to mountains of central and southern Arizona and southwestern New Mexico. It prefers oak (Quercus) woodlands but also occurs in oak-pine (Quercus-Pinus) woodlands of higher elevations, and in riparian woodlands. Smaller and more acrobatic than other titmice, the Bridled Titmouse acts more like a chickadee than a titmouse.
During the nonbreeding season this species often flocks with other insectivorous birds, such as chickadees, kinglets, warblers, vireos, tanagers, nuthatches, and creepers. Like many other titmice and chickadees, the Bridled Titmouse plays a key role in mixed-species flocks as a nuclear species that attracts other birds, often leading flock movements and initiating alarm calls when danger threatens. While resembling other North American titmice in most aspects of its behavior, the Bridled Titmouse is unusual among parids (chickadees and titmice) in often having a helper that assists with some breeding activities.
Until recently, it was thought that the Bridled Titmouse might be a New World relative of the Old World crested tits (subgenus Lophophanes), which also have crests and similar facial patterns. Molecular analyses (allozymes, mitochondrial DNA, and DNA-DNA hybridization), however, have revealed that the Bridled Titmouse is more closely related to the other North American titmice: Tufted (B. bicolor), Oak (B. inornatus), and Juniper (B. ridgwayi) titmice.
Much remains to be discovered about the biology of the Bridled Titmouse. Little detailed information is available, except for studies of song ( Gaddis 1983a ) and foraging ecology ( Dixon 1961 , Nocedal 1994a ). The presence of helpers (Nocedal and Ficken in press) points to the need for more extensive studies of breeding biology, and many unanswered questions also remain about the behavior of this titmouse in mixed-species flocks during the nonbreeding season.