Mockingbirds & Thrashers (Family: Mimidae)

Mimids are medium-sized, longtailed, generally solitary songbirds "well known for their vocal repertoires and mimicking abilities" (Sibley 2001, p. 468), who "forage mainly on the ground, using their long, sturdy bills to toss leaves and sticks, raking the dirt in search of food. Most species frequently run on the ground with their tails raised", (Sibley 2000, p. 410) and often run to escape danger rather than flying. Among the four species of Mimid found in our area (three species of thrasher and the Northern Mockingbird), the latter is the ecosystem "generalist" of the group, living in a wide variety of habitats and having a much wider geographical spread (from coast to coast throughout North America well south into Mexico), while the thrashers are ecological specialists -- the three thrasher species found in the desert southwest have overlapping ranges, but each prefers a different habitat.

So far in Saguaro Juniperland, we have been remiss in photographing these birds. However, in September 2007, we encountered a nest in a Jumping Cholla Cactus tree which reflects the style (very likely) of one of these birds. We can't say which one, but Sibley's Guide to Bird Life and Behavior (2001) provides a useful array of clues that lead us to suspect that the nest's former occupant was a Bendire's Thrasher. (See more now below.)

We see three kinds of Thrashers -- Bendire's, the Crissal, and the Curve-billed -- on our Saguaro Juniper lands, and they appear to stay here all year long. While their ranges overlap, "the Crissal Thrasher prefers more vegetated desert washes and dense thickets of mesquite" (Sibley 2001, p. 470), the Curve-billed lives "most frequently in cactus-rich deserts intermixed with mesquite" (ibid.), while Bendire's "has a decidedly local distribution in Arizona: it frequents deserts dominated by cholla cacti [and] slightly higher-elevation grassland-desert habitats with yucca...." For this reason, we will place our description of the nest in question under the heading of

Bendire's Thrasher (Toxostoma bendirei)

This Thrasher below -- apparently a Bendire's, though the detail is not very good and it might be a Curve-billed -- was observed sitting on a railroad-tie fencepost at the Gate to Section 8 on the Pool Wash Ridge Road September 24, 2004. (Click on each image to enlarge it.)

..

Now, note that the following nest identification is speculative -- we did not see the bird, only the nest. Curve-billed Thrashers also build nests of such kind in cholla cacti. Note also that the location of this sighting was nearly 20 miles south of Saguaro Juniper proper -- at the terrace lining the south flank of Tres Alamos Wash near Milepost 5 on the Cascabel Road. Below left, a view on the terrace, with its characteristic Chihuahuan Desert/Apache Highlands vegetation: Jumping Cholla Cactus admidst fields of grasses, ocotillo, and Whitethorn Acacia. (Click on each image to enlarge it.) We took a few minutes to search for bird nests in the cholla, and were rewarded with a single find, below center, a fine nest deeply embedded in the forbidding barbed spines of this cholla. At right, the structure of the nest itself shows an outer framework of enthorned Whitethorn Acacia sticks, with an inner bed of fine grasses.

....

Below left, a closer view of nest structure, showing the Whitethorn Acacia framework to be roughly rectangular, the protection amounting almost to a "Crown of Thorns" imagery. At center, the fine-grass bedding viewed from above. At right, just adjacent to the Cholla with its nest, the ubiquitous Whitethorn Acacia, very characteristic of this ecozone. (Click on each image to enlarge it.)

....

 

Curve-billed Thrasher (Toxostoma curvirostre)

Below, a Curve-billed doing what they do best -- stalking along, looking/listening while cocking its head, and thrashing the soil-litter with the large, curved bill in order to dislodge insects concealed there. (Click on each image to enlarge it.)

....

 

Northern Mockingbird (Mimus polyglottos)

We have seen this bird catch a Banded Gecko (which was running up the side of a wall) on the fly. It is a very effective predator of small reptiles and invertebrates. This bird is also "known for its astonishing ability to mimic other species' songs" (Sibley 2001, p. 468), including the learned mimicry in Arizona of parts of songs that could only have been heard in the birds' southern wintering grounds (ibid. p. 472). Northern Mockingbirds' song phrases are however "stereotyped, each individual using a repertoire of 150 to 300 phrases and repeating them the same way every time", a pattern that differs sharply from some of the thrashers, who improvise as they sing (ibid. p. 473).

Return to Birds