smallbilledthrasher

REVIEW OF THE SMALL-BILLED THRASHER.

The Small-billed Thrasher is a vernacular name which I have bestowed upon what has been called Bendire's Thrasher.  It was also originally called the Bendire's Mocking-thrush.

Toxostoma bendirei  (Coues, 1873)

Harporhynchus Bendirei  Coues, 1873

Methriopterus bendirei  (Coues, 1873);  Ridgway, 1882

My first observation of this species included an actual sighting of the subject, presumably a male thrasher, which also produced a concert of vocalizations.

Video 

https://www.youtube.com/watch?v=EvHareDSC7s

12 April 2023.

iNaturalist record  https://www.inaturalist.org/observations/155054785

The above image is an illustration of this species by Mathew Louis, 2022. 

The small-billed thrasher was first described as a species by Elliott Coues in June, 1873 in The American Naturalist, vol. VII (6): 330.  The first specimens were collected near Tucson (Fort Lowell), Arizona Territory, in 1872 by Charles Bendire.

Coues, Elliott (1873).  "Some United States birds, new to science, and other things ornithological."  The American Naturalist.  7(6):321--331.  See Figure 69, p. 329 (illustrator not identified).

Specimen 100504

https://www.si.edu/object/nmnhvz_4294312

Specimen 100505

https://www.si.edu/object/nmnhvz_4294311

DISTRIBUTION

T. bendirei  United States:  Arizona, New Mexico, Colorado, Nevada, Utah, California.  Mexico:  Sonora, Sinaloa, Baja California.  (Canada:  see below).

T. bendirei candidum  Desert of western Mexico in western Sonora.

T. bendirei rubricatum  Interior of southern and central Sonora and the coastal areas near Isla Tiburón.

SUBSPECIES

The nominate subspecies is the only one which nests in the United States.  The two subspecies which are given below are probably not, in my opinion, readily distinguishable from the nominate in field observations.

+  Toxostoma bendirei candidum  van Rossem, 1942

Transactions of the San Diego Society of Natural History (9)33:377--384 (381).  "Notes on Some Mexican and Californian Birds, with Descriptions of Six Undescribed Races."  Type:  Guaymas, Sonora, Mexico (Dickey collection, San Diego).

The coloration is "everywhere paler; dorsally more ashy brown, ventrally very much whiter, with flanks and under tail coverts pale grayish buff."

+  Toxostoma bendirei rubricatum  van Rossem, 1942

Transactions of the San Diego Socierty of Natural History (9)33:377--384 (381--382).  "Notes on Some Mexican and Californian Birds, with Descriptions of Six Undescribed Races."  Tecoripa, southeastern Sonora, Mexico (Dickey collection, San Diego).

It is distinct from the nominate in having "darker and redder (less grayish brown) ventral coloration, particularly on flanks and under tail coverts, though with a rusty wash over the whole under surface; spotting more prominent and more generally distributed in series.  Dorsal coloration slightly darker and more reddish brown, particularly on rump and upper tail coverts."

https://www.birdforum.net/opus/Bendire%27s_Thrasher

CURRENT STATUS AS A VULNERABLE SPECIES

The small-billed thrasher is now listed by the IUCN (International Union for the Conservation of Nature and Natural Resources) as a Vulnerable species, and its status had been upgraded to this on May 1, 2004, having been previously a Least Concern species.  The population was then estimated to include 170,000 mature individuals.

https://www.iucnredlist.org/species/22711108/179833350#population

There are at present estimates about 83,000 mature adults.  The population has decreased within the past forty years by 91% and is in a continuous decline.  Its status as a Vulnerable bird species has been continued following the recent review of it by the IUCN in 2020.  

The above map indicated the breeding areas in Arizona of the small-billed thrasher from a survey of this species conducted 1993--2000.  Black squares indicated that breeding was confirmed, and Gila and Greenlee counties were the only counties in the state where it was not.  Blue-green squares indicated that breeding was probable (as was denoted for Greenlee County), and white squares indicated that breeding was possible.

In Arizona, some 324 areas (quads) were assessed in the survey where the thrasher was found or presumed to be found nesting, yielding roughly 192 areas for which it was confirmed (133) or presumed to be probable (59).  

The types of habitat where it has been found include the following.

Desertlands----Sonoran desertscrub:  paloverde (Parkinsonia), Olneya ironwood, mesquite (Prosopis), acacia and catclaw (Acacia), saguaro (Carnegiea), cholla (Cylindropuntia), barrel cactus (Echinocactus), Opuntia prickly pear, creosote (Larrea), jojoba (Simmondsia), and Canotia thorns.

Lower Colorado River biome lacking saguaros (Carnegiea):  mesquite, creosote, white bursage, brittlebush, saltbush

Wetlands----dry Sonoran riparian scrublands:  mesquite, paloverde, ironwood, burrobush, desert broom, quailbush, desert willow (Chilopsis linearis)

Grasslands---Semiarid grasslands:  sotol, agave, snakeweed, burroweed, yucca, mesquite

Agricultural areas:  scattered farmlands, pastures, canals, feedlots, and ponds.

Grasslands--Cold/Temperate (Great Basin) Grassland:  pinyon pine (i.e. Pinus edulis), juniper (Juniperus).

Desertlands----Cold/Temperate (Great Basin) Desertscrub:  sagebrush (Artemisia), blackbrush (Coleogyne ramosissima), shadscale (Atriplex confertifolia).

The Small-billed Thrasher is a host of the brood parasite Brown-headed Cowbird  Molothrus ater [obscurus].  This has been substantiated by the 1885 collection of materials from Red Rock, Arizona.  See Friedmann, Bulletin of the United States National Museum, 233: 71.

ALBERTA

There is a single record of Toxostoma bendirei from Alberta, this establishing the thrasher as also a Canadian species.  It was reported on May 28--30, 1988 at Buffalo Prairie in Jasper National Park of Canada in the Banff region.  See Canadian Field-Naturalist 106:404--405 (Mills, 1992), which includes a photograph of the subject.

SASKATCHEWAN  (hypothetical record)

From the above report I was able to trace reference to the small-billed thrasher in Saskatchewan.  It was reported there May 27, 1972 in Dundurn.  See also American Birds, 26:774.

MANITOBA  (hypothetical record)

From the above report in Canadian Field-Naturalist I was also able to trace reference to a record of it in Manitoba.  It was reported there May 14, 1974 in Grand Beach.  See also American Birds, 28:814.  Neither this sighting nor the sighting in Saskatchewan were substantiated to be accepted by a records committee.

Avian Conservation and Ecology  

https://ace-eco.org/vol18/iss2/art2/

NEVADA  Statewide status:  Critically Imperiled

UTAH  No status defined.

Navajo Natural Heritage Program:  Vulnerable

CALIFORNIA, ARIZONA, NEW MEXICO (each):  VULNERABLE

COLORADO

TEXAS

Certain maps suggest that its distribution may fall into extreme western Texas, but this is an error.  There are unconfirmed records of the thrasher in Texas, and it is thus Hypothetical.  There have been reports of a 1955 sight record in Randall County near Amarillo as well as those in Eagle Pass.

BAJA CALIFORNIA SUR

Certain maps indicate that its distribution (breeding or general) includes this state, but this is an error.

ARIZONA WILDLIFE CONSERVATION STRATEGY

(above map)

https://awcs.azgfd.com/species/birds/toxostoma-bendirei 

SGCN (Species of Greatest Conservation Need) Tier 2 species {2022}.  In 2012, its ranking was 3 under the same guidelines.  SGCN species are ranked one to three based on their respective conservation needs as determined by the Arizona Game and Fish Department, with the lower score denoting those species being subjected to the greatest risks.  (Thus, its status has been upgraded in the past decade.)  

Other rankings from Arizona Game and Fish are as follows:

Extirpated Status; Federal [and] State Legal Status; Disjunct Status; Demographic Status; Concentration Status; Distribution Status:  each Tier 2

Declining Status:  Tier 1  In Arizona, its decline over the past twelve years has been by more than thirty percent.

STATUS OF OTHER TOXOSTOMA SPECIES IN THE NEARCTIC REGION (UNITED STATES, CANADA, MEXICO)

TOXOSTOMA LECONTEI:  SCCN Tier 2  It is also a species which is in decline in Arizona.

TOXOSTOMA GUTTATUM (Cozumel Thrasher):  Critically Endangered species (IUCN) in neotropical Mexico (Cozumel); last sight record 2006.  Possibly extinct.  It is closely related to T. rufum (Brown Thrasher).

BANDING CODE OF TOXOSTOMA BENDIREI:  BETH

PROPOSED BANDING CODE OF THE SMALL-BILLED THRASHER:  "SBTH"

ABA (AMERICAN BIRDING ASSOCIATION) CODE:  2

FRENCH VERNACULAR NAME (ABA):  Moqueur de Bendire  

PROPOSED FRENCH VERNACULAR NAME:  "Moqueur à petite bec"

Per the decision of the American Ornithological Society, an additional, substitute vernacular name differing from that which I have proposed for it may also be made.  (This is a pending decision).

----

2024.

+  List of my other records to eBird which were determined to be UNCONFIRMED.  This also includes a note about a record of the Eared Quetzal (Euptilotis), a species which I have not yet observed.