Pipilo maculatus arcticus, P. m. montanus
Status: Common regular breeder western Panhandle, hybrids and introgressants with Eastern Towhee elsewhere except extreme southeast. Uncommon spring and fall migrant statewide. Rare regular winter visitor southeast, rare casual elsewhere.
Documentation: Specimen: UNSM ZM7252, 24 May 1900 Monroe Canyon, Sioux Co. An intergrade specimen was collected near Lisco, Garden Co 12 Jun 2018 and deposited in the Cornell University Museum of Vertebrates.
Taxonomy: There are 19 subspecies currently recognized (AOU 1957, Pyle 1997, Gill and Donsker 2017), 10 in Mexico and Central America. The other nine occur north of Mexico and are often divided into two groups, Coastal, including four subspecies limited in distribution to the Pacific Coast from British Columbia southward, and Interior, including five subspecies: falcinellus, resident in southern Oregon to central California, curtatus, breeding in interior southwest Canada and interior northwest USA and wintering to southern California and southern Arizona, montanus, breeding in southwest USA and northern Mexico and wintering to southwest Texas, arcticus, breeding from central Alberta, central Saskatchewan, and central North Dakota, south, east of the Rocky Mountains, to southeastern Wyoming, northeast Colorado, and central northern Nebraska, and wintering to southwest New Mexico and south Texas, and gaigei, resident in southeast New Mexico and west Texas.
Nebraska breeding birds are arcticus (AOU 1957). There is but a single specimen record of montanus taken 5 Oct 1915 at North Platte, Lincoln Co; the remains were “badly decomposed” but parts were submitted to H. C. Oberholser, who confirmed that the bird was indeed montanus (Swenk 1918, Tout 1947). Subspecies montanus has been recorded in Morton Co, Kansas (Johnston 1965, AOU 1957), is at least partly migratory, and, although its breeding range is mostly west and south of Nebraska (Bartos Smith and Greenlaw 2015), it includes the Front Range of Colorado, where it is “very common” (Steven Mlodinow, personal communication). In northeastern Colorado, along the South Platte River, both arcticus and montanus have been reported, along with a large number of hybrids/intergrades, notably at Tamarack WMA in Logan Co (Steven Mlodinow, personal communication). Nevertheless, approximately 80% of the Spotted Towhees in Logan and Sedgwick Cos are montanus (Steven Mlodinow, personal communication) and so its occurrence in Nebraska would not be unexpected. Recently, Mlodinow found that during migration a “goodly percentage” of the Spotted Towhees at Oliver Reservoir, Kimball Co, Nebraska were montanus, including one there 13 Apr 2019 (eBird.org, where entered as “maculatus group”), but none were found in the North Platte River Valley, where only arcticus occurred in Scotts Bluff Co and at Ash Hollow SHP, Garden Co. There is a surprisingly northerly Nebraska record of two on East Ash Creek, Dawes Co 14 May 2019 (Mlodinow, Remsen; numerous photos; eBird.org); likely the same two were there 15 Jun 2019. As a note of caution, Mlodinow (personal communication) stated: “The NE breeding SPTO have more/larger spots above and more extensive white below the tail (on folded tail, white nearly reaching tip of under tail coverts) compared with CO SPTO. Being subspecies, it is unclear how much variation each taxon would entail, so I typically only [identify] those that seem distinctive and that I can photograph. I am impressed by how much the two populations differ as a whole.” Mlodinow found another montanus at Wildcat Hills NC, Scotts Bluff Co 30 Jul 2019 (eBird.org, photo).
Although introgression between Spotted and Eastern Towhees on the Great Plains is well-known (Sibley and West 1959, Short 1961, Bartos Smith and Greenlaw 2015), the two are currently considered separate species (Banks et al 1995). Strong genetic differences between Eastern and Spotted Towhees, including absence of shared haplotypes, were demonstrated by Ball and Avise (1992), although, since their samples were from western and eastern extremes of the North American range (Washington, South Carolina, Georgia), this result was not unexpected. Re-evaluation of data in Sibley and West (1959) that showed 56% of individuals in the “hybrid zone” were presumed phenotypic Eastern and Spotted Towhees was considered indicative of assortative mating and strongly supportive of species status (Banks et al 1995), despite the presence of “hybrids” over most of the state (Sibley and West 1959, Greenlaw 2015). A recent study (Silcock, unpublished data) analyzing ranges of towhees in Nebraska based on reports from eBird (eBird.org) of phenotypic Spotted and Eastern Towhees showed that >90% of towhees in the western two-thirds of the state were reported as Spotted, and >87% of the reports along the east edge of the state as Eastern, with a “overlap zone” where the two occur in roughly equal numbers (see Figure 1). These data support the conclusion by Banks et al (1995) and Sibley and West (1959) that assortative mating is occurring, apparently at an important level. In the absence of genetic studies, however, it is unknown what proportion of towhees reported in eBird as Spotted Towhees might be introgressants, a point noted by Scharf (2005), who focused on phenotypic Eastern Towhees in his study because birds with any degree of white spotting on their upperparts were likely to be of indeterminate genotype.
Sibley and West (1959) suggested that one factor leading to assortative mating might be correlation of degree of back spotting pattern with climatic differences, in particular the amount of shade in towhee habitat (more in eastern forests than in western open brush). Anecdotal information supporting this theory was provided by T. J. Walker (personal communication), who observed that in his southeastern Lincoln County, Nebraska survey area “I have noted for years that the [Spotted Towhee] songs vary quite a bit – in areas with more deciduous woodland and cedar coverage most of the songs, while still typical of Spotted, have a little hint of “Eastern” to them. In the areas of the canyons with very little woodland, where the landscape is mostly grassland with shrub thickets the songs are quite “dry” and clearly Spotted.” These considerations raise the possibility that towhees of apparent intermediate plumages and songs are not necessarily introgressants, but might include individuals of sub-populations distributed regionally that have adapted over time to local environmental conditions. If this is true, and introgressants occur in relatively low numbers, the distribution across Nebraska of the degree of back and wing spotting and wing patch extent would be expected to be clinal in both species, reflecting local environmental conditions. Sibley and West (1959) pointed out that contact between Spotted and Eastern Towhees in Nebraska was not on a broad front but limited to riparian corridors, and surmised that this resulted in “greatly restricted” gene flow, although currently, some 60 years later, riparian corridors are significantly more vegetated and presumably not as restrictive to gene flow as in 1959 (Williams 1978, Knopf 1986, Davis 2005).
In recent years there have been several documented reports in Nebraska of towhees resembling phenotypic Spotted or Eastern Towhees far from their respective expected summer ranges. In Scotts Bluff County there were six reports of up to six birds at four locations of phenotypic Eastern Towhees in summers 2013-2017, including males singing Eastern songs, and a male “unspotted, singing an Eastern song” (Kathy DeLara, eBird.org). In extensive surveys in the 2000s in Lincoln County, T.J. Walker found 22 Eastern Towhees among the 2307 towhees detected. Data (Silcock, cited above) show that in both counties, however, Spotted Towhees account for 98-99% of towhees. In Keith County, Eastern Towhee is a “rare summer resident”, although only two records are cited; one was seen in 2004 that looked like an Eastern Towhee but sang a Spotted Towhee song (Brown et al 2012). Scharf (2005), during a four-season netting study in the “nesting season”, found 20 Eastern Towhees of phenotype category “0” (“pure” Easterns, per Sibley and West 1959) along the Platte River in Dawson Co 2001-2004. In the east, phenotypic male Spotted Towhees singing Spotted songs were carefully studied at Rose Creek WMA, Jefferson Co 27 Jul 2016, and another was near Steele City, Jefferson Co the same day. A male at Schramm SP, Sarpy Co 21-29 May 2005 that looked and sang like a Spotted Towhee possessed about half of the white primary patch typical of Eastern Towhee.
In this context, it is of interest that Zink (1994, Table 3) found that in three plumage groups of Fox Sparrow, iliaca, unalaschcensis, and schistacea, nine of 139 samples had mtDNA that did not match the plumage type. Similarly, Wright (2019) noted that “classic … Cassiar-like males [of Dark-eyed Junco] have been photographed as far east as Nova Scotia and New Jersey… but there can be no certainty that the birds are not hybrids….”.
It is clear from this discussion that more study of the distributions of Eastern and Spotted Towhees in the breeding season in Nebraska is needed. It has been assumed that introgression occurs statewide, but the relative contributions of genetics and adaptation (controlled presumably by assortative mating) to the distributions of phenotypic Eastern and Spotted Towhees and putative introgressants is unknown. There have been no genetic studies of this area of species overlap in Nebraska.
Spring: Mar 22,23,25 <<<>>> summer (central), Apr 9,10,11 <<<>>> summer (west), winter <<<>>> May 22,23,24 (south and east)
In central and western Nebraska, where wintering is rare, arrival is in late Mar and early Apr, with central birds arriving significantly earlier. There is an earlier Panhandle report 13 Mar 1957. Wintering birds in the south and east probably depart by mid-May, although last dates are difficult to determine due to the presence of intergrades that are often reported as this species.
- High counts: 85 at Lake Ogallala, Keith Co 30 Apr 2000, 45 at Lilley’s Sandpit, Hall Co, 9 May 1998, and 42 in Hall Co 11 May 2002.
Summer: BBS data 1966-2015 (Sauer et al 2017) show fairly even distribution within the virtually statewide range (but see discussion under Taxonomy, above), with perhaps higher numbers in southwestern and northwestern Nebraska. BBS trend analysis shows Spotted Towhees have increased 3.86% (95% C.I.; 0.77, 6.88) per year in Nebraska 1966-2015 (Sauer et al 2017).
- Breeding phenology:
Eggs: 22 May-25 Jun
Nestlings: 8 Jun
Fledglings: 18 Jul
Fall: Sep 15,17,18 <<<>>> winter (southeast)
An earlier arrival in the east was one in Lancaster Co 12 Sep 2014.
Most departing birds leave the summer range by late Oct, although lingering birds make determination of departure dates difficult. The last seen in Valentine in 2016 was on 9 Oct.
A large total of 120 were banded in the period 24 Aug-7 Oct for the 2015 fall season at Wildcat Hills NC, Scotts Bluff Co, indicating peak fall movement occurs there in Sep.
Significant movement into the southeast begins in late Sep; it was “common” in Omaha in early Oct 1975 (Williams 1976). The first “spotted” birds appear in Missouri in early Oct (Robbins 2018)
- High counts: 60 near Gibbon, Buffalo Co 10 Oct 1998, 40 in northern Lancaster Co 17 Oct 1998, and 35 at Wildcat Hills NC 24 Aug 2015 (banded).
Winter: CBC data indicate that this species is still rather evenly distributed statewide in Dec, although numbers are lowest in the Panhandle and the north. By Jan, reports from the west and north are few; numbers are lowest in Feb, when most are in the southeast.
A note regarding Pipilo towhees on the Seward-Branched Oak CBC is of interest, suggesting no overlap of Nebraska winter ranges: “I checked and we have had eastern towhees on the count only three times since 1993. In contrast, we have had spotted towhees 13 times (plus one count week bird). We have never had both species on the same count” (Joseph Gubanyi, pers. comm.).
There are 13 winter reports Jan-Mar from the North Platte Valley, and these others from the north and west: 31 Dec 2005 Crawford CBC, 1 Jan 1957 Logan Co, 2 Jan 2010 Lake McConaughy CBC, 3 Jan 2011 Sutherland, Lincoln Co, 12 Jan 2014 Knox Co, 14 Feb 1993 Antelope Co, 23 Feb 1957 Thomas Co, 3 Mar 1958 Sheridan Co, and 3 Mar 2019 Rock Co.
BBS: Breeding Bird Survey
CBC: Christmas Bird Count
SP: State Park
UNSM: University of Nebraska State Museum
WMA: Wildlife Management Area (State)
Photograph (top) of a Spotted Towhee at Fontenelle Forest, Sarpy Co 30 Oct 2008 by Phil Swanson.
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Birds of Nebraska – Online