Identifying Wrentit and similar songbirds

Author’s note: As I fill in for Kenn Kaufman while he works on a book project, I want to acknowledge his stellar role in sharing with birdwatchers at all levels of experience his wealth of natural history knowledge, especially about bird identification, status, and distribution and the history of birding. My birding experience is largely centered in California and adjacent regions, more restricted than Kenn’s broad geographical wisdom. And while my future “ID Tips” articles will be relevant for readers across North America north of Mexico, my initial effort here treats a bird you’ll likely never see away from the coastal slope of Oregon, California, and northwesternmost Baja California.

This column focuses on a bird confined to the Pacific states, from extreme northwestern Oregon south barely into Baja California. It isn’t prone to wander, so it’s unlikely to be seen outside its well-defined range. So why is the Wrentit of interest to birders in the other 90 percent of North America? Certainly its uniqueness and interesting evolutionary and biogeographic history play a role. And it’s not a slam-dunk identification; the bird is a non-descript skulker, superficially combining — as the name suggests — characters of different small songbirds. The overall brownish coloration, affinity for dense brush, and tail-cocking habit are reminiscent of many wrens. Strong legs and a fairly short bill with slightly downcurved culmen recall titmice and chickadees. Even within its range, observers frequently mistake other species for it, which can cause headaches since records only a few miles out of range or habitat would be highly significant.

The Wrentit is surely a “plain brown job,” but closer inspection shows complexity and beauty in its colors and patterns. The breast has a pinkish tinge, subtle streaks line the underparts, and the bird has a staring whitish iris. Males and females are essentially identical; juveniles are best told by subtle differences in the ring of color around the white iris.

Detecting and identifying the Wrentit starts with its vocalizations. In the words of William Leon Dawson, the poet laureate of California ornithology, “Indeed, it is safe to say that the bird is heard a thousand times to once it is seen.” The male’s song is a classic “bouncing ball” pattern of several single peep notes that then rapidly accelerate into a loose trill. Female song, often in a duet with the male, is a slower series of single notes that does not accelerate. The songs are audible for some distance across the brush-cloaked hillsides. At close range, you’ll hear the common call — a rapid purring series of atonal notes.

Much of what we know about Wrentit life history comes from Mary M. Erickson’s studies. A student of Joseph Grinnell’s, she conducted detailed work in the 1930s near the University of California, Berkeley, campus. Long-term banding studies in Marin County, California, have filled in many more details. Slight range expansions in recent decades may be due to enlightened replacement of sterile turf with native and other drought-tolerant shrubs in residential areas and from an expansion of shrubby habitats following heavy commercial logging. But work by Michael Soule and colleagues around San Diego showed how fragmentation of habitat through urban development has also caused the loss of some populations.

Vagrancy in birds is chockfull of surprises. It is increasingly clear that nearly all bird species may wander “out of range,” greatly so in many migratory species. But if you’re birding east of the Pacific states, don’t hold your breath for a wandering Wrentit. Extreme sedentarity is a hallmark of these birds, which may spend their lives in real estate not much larger than a football field.

Although this Wrentit hails from the same area as the bird in the photo on the left, it is a bit browner (less gray) overall, perhaps due to some combination of lighting and individual variation. This gray to reddish-brown spectrum is also reflected in geographical variation in the Wrentit; the ruddiest birds occur in the north coastal range of the species in Oregon and northern California and the palest and grayest birds are found in the interior and south. There are five generally accepted subspecies of Wrentit based on plumage color and, to a lesser extent, on tail length. But, as with so many named subspecies of birds, some of these represent attempts to fit continuous and often subtle variation into discrete taxonomic units.

Subtle at times, but more obvious in many views, the streaking through the underparts of the Wrentit sets it apart from other small, drab gray or brown denizens of extensive shrubby habitat such as Bushtits, wrens, and gnatcatchers, all of which lack these longitudinal streaks. Such a feature can be hard to observe in the complex shadows and obscuring branches that Wrentits hide within, but the patient birder is sometimes rewarded with more open views such as this. Note that the rather “loose-jointed” tail is habitually held up at a sharp angle — during the Wrentit’s short flights, the tail is pumped up and down, as if assisting the short, rounded wings in keeping the bird airborne.

It’s not often you’ll see a Wrentit in the open on a rock like this. It’s a bird with a penchant for remaining within the dense, stiff-twigged vegetation of chaparral, sage scrub, and the understory of oak and riparian woodlands. Nevertheless, describer William Gambel gave this bird the English moniker “Ground-Tit,” as they often drop to the ground under their cloak of shrubbery to forage among the leaf litter. And the generic name Chamaea comes from a Greek root meaning “on the ground.” One might facetiously argue that a key identifying character of the Wrentit is the difficulty one experiences in seeing one! And this challenge underscores the importance of learning their frequent and distinctive calls.

It’s taxonomically neither “wren” nor “tit,” but the Wrentit’s name does acknowledge its superficial similarity to both of these groups. On the West Coast, the Bewick’s Wren, like the one pictured here, almost inevitably shares the Wrentit’s brushy habitat, and the two species are often in close proximity. Like the Wrentit, it is a rather uniform gray and brown bird that often holds its long tail cocked upward. But the similarities end there — the wren shows a bold white eyebrow, a dark eye, black barring and white fringes on the tail, and black bars on the undertail coverts. And note the wren’s long and slender bill.

The “tit” part of “Wrentit” refers once again to a superficial morphological similarity to the titmice and chickadees in the family Paridae. But perhaps the most similar “tit” species, and a closer cousin to the Wrentit than the parids, is the Bushtit. Long-tailed and plain gray-brown, with a similarly stout bill, the Bushtit’s appearance (and name) can cause confusion with the Wrentit. Adult female Bushtits, like the bird pictured here, have whitish eyes, as do Wrentits. But the smaller Bushtits almost always travel in groups — even in the dozens — and fly readily across open gaps between trees and shrubs. They are extremely acrobatic, often hanging upside down or head-down. And they keep up a constant chatter of soft “pit” notes unlike any Wrentit vocalizations.

Though localized and of conservation concern, the California Gnatcatcher is another relatively non-descript gray-brown skulker in dense scrub vegetation that shares a portion of the Wrentit’s range on the coastal slope of southern California. Black-capped breeding males are distinctive, but plainer females with brownish plumage tones can recall a Wrentit. Like Wrentits, they are usually found in pairs and are often ensconced well within tracts of sage and other shrubs. But these gnatcatchers show a thin white eye ring (the eye itself is dark), a very thin bill, and a blackish tail with some white at the corners; they lack any hint of streaking on the breast. And the calls are very different — soft scolds and a distinctive kitten-like mewing.

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Classifying the Wrentit

In 1845, William Gambel first described the Wrentit to science as Parus fasciatus, linking it with titmice and chickadees, along with some other small insectivorous birds. A scant two years later, Gambel recognized its uniqueness by erecting the genus Chamaea for it. The Wrentit resided in its own family (Chamaeidae) for many decades. But even as early as the latter half of the 1800s, several noted ornithologists acknowledged that it might have its roots among the “Timeliidae” (now Timaliidae) — a diverse Old World group known as babblers — and this was confirmed by Charles Sibley and Jon Ahlquist’s DNA-DNA hybridization studies in the early 1980s.

More recent comprehensive genomic work has clarified relationships within the “babbler assemblage,” bringing into the babbler fold one group of “Old World warblers” (Sylvia and relatives) as well as the Asian parrotbills (often placed in the family Paradoxornithidae). Current taxonomy retains one segment of the babbler radiation, including the Wrentit, Sylvia warblers, parrotbills, and a few relatives, in the family Sylviidae, while other relatives among the babblers remain in the family Timaliidae (along with other related families within the babbler radiation, all in Asia and other parts of the Eastern Hemisphere). No matter where these lines are drawn, it is clear that the ancestor of the Wrentit colonized the Americas via the Bering land bridge, as all its relatives are exclusively Old World.