MVAS Bird of the Month is the reclusive Crissal Thrasher

Jay Wilbur (Mesilla Valley Audubon Society) | July, 2017 | Columns, Features


Crissal Thrasher

Crissal Thrasher. Photo by Jay Wilbur.

For most people, seeing a Crissal Thrasher is an unlikely event. But for local birders who know the habits and habitat of this reclusive bird, it is spotted regularly, if only fleetingly. The effort necessary to seek out and view this species is well worthwhile, for it is one of the most striking birds in our region.

Even before you see one, you might find the very name intriguing. Hearing the words “Crissal Thrasher” for the first time could easily evoke an odd, sardonic dread, as if a Batman villain were about to jump out of the bushes. But in fact, the name is perfectly accurate and descriptive.

Thrashers are a group of bird species that make their living by foraging on the ground and in low brush. A defining behavior is using their bills to swish and swat away ground clutter to find food, mostly insects. They rapidly twist their head, left then right, “thrashing” the leaves and twigs with their swinging bill, hoping to bring some hapless bug into sight. Many Thrasher species even dig holes into loose soil this way to reveal their prey.

The Crissal Thrasher gets its first name not from some 19th century ornithologist, but rather from one of its most dramatic and distinguishing field marks, the color of its crissum. A bird’s crissum is the body part that performs a couple of functions, including the reproductive act. On a Crissal Thrasher, it is covered by bright, rust-colored feathers that strongly contrast with the drab gray feathers on most of the rest of its body. This contrast is unique among Thrashers, and so became a straightforward way to identify the species.

But a rufous crissum is certainly not the only distinctive field mark displayed by the Crissal. It also sports a very impressive bill. Relative to its head size, it has one of the longest and most curved bills of any bird, even compared to its Thrasher cousins. Ironically, its bill is longer than that of the Long-billed Thrasher, and more curved than the Curve-billed Thrasher’s. Clearly, it is well endowed with a tool perfectly adapted for thrashing up a living from its desert habitat.

The Crissal Thrasher is a non-migratory resident of the desert Southwest. It stays put in dense brush around desert washes. It almost always sees you, and flees along the ground, long before you get close. If you see it at all, it is usually a split-second glimpse of a distant, rapidly retreating bird with its long, gray tail raised, showing, you guessed it, those rusty undertail covert feathers.

But there is the occasional exception. Crissals attract mates by singing. When they are so preoccupied, a stealthy birder can sometimes get lucky enough to sneak up for a longer peek at one. Of course, you hear it singing before you get close enough to see it, so it’s a good idea to know what its vocalizations sound like.

Like all Thrashers, Crissals are in a group of birds called Mimids. The best known of these is the Northern Mockingbird. Like the Mockingbird, Crissals mimic the songs of other birds. But unlike the harsh and repetitive Mockingbird, the Crissal strings its imitative song snippets into a soft and melodic recital. This odd looking and oddly named bird is unquestionably one of our most beautifully sounding songbirds. So, even if you aren’t lucky enough to spot one, perhaps you’ll at least get to hear one on your morning walk.



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