For most of the 20th century, the Red-naped Sapsucker (Sphyrapicus nuchalis), the Yellow-bellied Sapsucker (S. varius), and the Red-breasted Sapsucker (S. ruber) were treated as belonging to a single species, S. varius (sometimes the Red-breasted Sapsucker was excluded). The three species are very similar, including genetically, and Red-naped Sapsuckers hybridize extensively with Red-breasted Sapsuckers (and, to a lesser extent, with Yellow-bellied Sapsuckers), but data on mating preferences has supported their status as biological species. (Howell 1952; Scott et al. 1976; Johnson and Johnson 1985; Cicero and Johnson 1995).
The Red-naped Sapsucker, which breeds across much of the western third of the United States and adjacent Canada, looks very similar to the eastern Yellow-bellied Sapsucker, but has a variable red patch on the back of the head, more extensive red on the male's throat, and red on the female's throat (absent from Yellow-bellied Sapsucker female's throat).
Red-naped Sapsuckers are common in summer in deciduous and mixed forests, especially around Quaking Aspens (Populus tremuloides), in the Great Basin and Rocky Mountain ranges, with a small number in the Sierra Nevada. They are rare west of the Sierra Nevada and very rare in the Pacific Northwest and west of the Cascades (where Red-breasted Sapsuckers are common). They occur casually east to the western Great Plains. They winter from southern California, southern Nevada, and central Arizona and New Mexico south to central Mexico.
(Kaufman 1996: Dunn and Alderfer 2011)
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Breeding
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) Nesting range includes the Rocky Mountain region from the southeastern quarter of British Columbia, southwestern and southeastern Alberta, western and central Montana, and the Black Hills of South Dakota south, east of Cascades and Sierra Nevada, to east-central California, southern Nevada, central Arizona, southern New Mexico, and extreme western Texas (Davis and Guadalupe mountains) (AOU 1998). During the nonbreeding season, the range extends from southern California (casually Oregon), southern Nevada, Utah, and central New Mexico south to southern Baja California, Jalisco, Durango, Coahuila, and Nuevo Leon (AOU 1998). Casual or accidental records exist elsewhere.
Coded range extent refers to breeding range.
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2014. The eBird/Clements checklist of birds of the world: Version 6.9. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
Habitat and Ecology
Comments: Breeding habitat is primarily coniferous forest that includes aspen and other hardwoods (AOU 1998), at elevations ranging from near sea level to 2,900 meters (Walters et al. 2002). In the Northern Rockies, the species is most abundant in cottonwood and aspen forests, also observed in other riparian cover types and in harvested conifer forests. Of harvest types, most observations were in patch cuts, seed-tree cuts, clearcuts, and older clearcuts. Birds in harvested stands and in drier conifer forests were probably associated with patches of deciduous trees (Hutto and Young 1999). In the Centennial Mountains, Idaho, sapsuckers used xeric tall willow communities (Douglas et al. 1992). In Wyoming and Colorado, sapsuckers were closely associated with aspen and mixed habitats (Finch and Reynolds 1988). In Colorado subalpine forests, they were significantly associated with habitats where aspen occurs near (less than 50 meters) willow, and used the willow for foraging (Ehrlich and Daily 1988, Daily et al. 1993). In the Pacific Northwest, the species typically breeds in aspen, riparian cottonwood, ponderosa pine, mixed conifer, and white fir forests (Bull 1978).
This species is a primary cavity nester that excavates nest holes in snags or living trees with a dead or rotten interior, and it shows a strong preference for aspen (Johnsgard 1986, Li and Martin 1991, Daily 1993;) but also uses paper birch, cottonwood, alder, western larch, ponderosa pine, Jeffrey pine, and lodgepole pine (Bent 1939, USDA Forest Service 1994). It especially favors aspen with heartwood decay brought about by shelf fungus (Fomes igniarius var. populinus), a heart rot that infects roots and dead branch stubs and spreads from the base of trees upward, but leaves the sapwood intact (Kilham 1971, Crockett and Hadow 1975, Daily 1993, Dobkin et al. 1995).
In a Colorado study, sapsuckers placed the first nest cavity close to ground and then excavated progressively higher cavities in subsequent years. Nest cavities were usually freshly excavated during the season of use and most nests were in trees bearing nest cavities excavated during previous years. Nest height averaged 2.7 meters in trees with no other cavities, 6.0 meters in trees with more than one cavity (Daily 1993). In a study in Colorado and Wyoming, sapsuckers used both healthy aspen and aspen infected by shelf fungus, nested in trees 17 to 42 centimeter dbh (mean 31 centimeter dbh) and used cavities that were 1 to 11 meters high (mean 5 meters; Crockett and Hadow 1975). In Colorado, abundance did not vary with differences in understories (herbaceous, short shrub, tall shrub) of mature aspen stands (Finch and Reynolds 1987).
In Oregon and Washington, the species is reported to nest in snags greater than or equal to 25.4 centimeter dbh at nest heights at least 4.6 meters (Thomas et al. 1979). In snow pocket and riparian aspen groves of the northwestern Great Basin, it used live trees more often than dead trees; nest trees measured 27 centimeter dbh and 14.6 meters high on average, were located an average of 20 meters from edges, and mean canopy cover was 76 percent (Dobkin et al. 1995). In western larch/Douglas-fir forests of northwestern Montana, it nested in both small and large trees, ranging from 22 to 119 centimeter dbh and averaging 58 centimeter dbh (McClelland et al. 1979).
In a study in mixed conifer forest in central Arizona, sapsuckers were strongly associated with large aspen (greater than 15 centimeter dbh), aspen snags, and large conifers (greater than 15 centimeter dbh), and negatively associated with shrub cover. Sapsuckers nested exclusively in aspen; mean nest height was 13.3 meters and mean dbh of nest trees was 37.1 centimeters (Li and Martin 1991).
Foraging includes drilling for sap in conifer (e.g., western larch, pine) and deciduous trees (e.g. aspen, willow, cottonwood, birch. In California, sapsuckers drilled in and around pitchy bole wounds on ponderosa pine that were the result of earlier overstory removal and porcupine feeding (Oliver 1970).
In migration and winter, habitat include various forest and open woodland habitats, parks, orchards, and gardens (AOU 1998). In southern California, winter habitats include riparian desert and other riparian habitats (USDA Forest Service 1994). In northwestern Mexico the species is found in forests and edge feeding at mid- to upper levels; it may overlap with wintering yellow-bellied sapsuckers in northcentral Mexico and red-breasted sapsuckers in northern Baja California (Howell and Webb 1995). In western Mexico, Hutto (1992) found red-naped sapsucker only in pine-oak-fir forest.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Arrives in northern Rocky Mountains mainly April-May, departs late summer to early fall. In California, migrates north between end of March to end of April; fall migration lasts from September through the end of October (USDA Forest Service 1994). A transient and winter visitor in northwestern Mexico from late September to mid-April (Howell and Webb 1995).
Comments: Drills rows of small holes in conifer and broad-leaved trees and drinks the sap that flows from these holes; also feeds on insects caught in the sap. Amount of sap taken and tree species used vary seasonally (Scott et al. 1977). Sap is most important in seasons when insects are not abundant. Also feeds on tree cambium, ants, beetles, wasps, caterpillars, beetles, and small amounts of fruit and berries (Scott et al. 1977, USDA Forest Service 1994).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 - 300
Comments: This species is represented by a large number of occurrences (subpopulations).
Comments: Total adult population size is unknown but likely exceeds 1,000,000. Rich et al. (2004) estimated population size at 2,200,000.
Considered a "double keystone" species for its role excavating nest cavities and drilling sap wells, both of which are subsequently use by other species (Ehrlich and Daily 1988, Daily et al. 1993). Nest cavities are subsequently used by secondary cavity nesters, such as tree swallows (TACHYCINETA BICOLOR), violet-green swallows (TACHYCINETA THALASSINA), mountain bluebirds (SIALIA CURRUCOIDES), chickadees (POECILE spp.), northern flickers (COLAPTES AURATUS), and house wrens (TROGLODYTES AEDON; Daily et al. 1993). In one study, tree swallows and violet-green swallows were restricted to groves occupied by sapsuckers (Daily et al. 1993). Sap wells are used by 40+ species, including hummingbirds, warblers, chipmunks, squirrels, wasps and butterflies (Phillips 1964, Daily et al. 1993).
Centers of breeding abundance in British Columbia, the northern Rockies, northeastern Oregon, and the Colorado Rockies (Sauer et al. 1997). In Pacific Northwest, territory size reported as 4 hectares (Bull 1978). In California, defends territories 0.6 to 6.0 hectares in size (USDA Forest Service 1994).
Hybridizes with red-breasted sapsucker (SPHYRAPICUS RUBER) and yellow-bellied sapsucker (SPHYRAPICUS VARIUS) where distributions overlap and may produce viable hybrid offspring; hybrid and backcross matings, however, are apparently selected against (Scott et al. 1976, Johnson and Johnson 1985).
Life History and Behavior
Lays four to five eggs incubated by both female and male; incubation 12-13 days; young altricial; 25-26 days to fledging; both sexes attend young (Ehrlich et al. 1988). In Colorado, nests with eggs recorded throughout June. Nestlings noted late June to mid-July in Montana and Wyoming (Johnsgard 1986). In central Arizona, 100 percent of 18 nests monitored successfully fledged young (Li and Martin 1991). Re-use of same nest tree, but with a new cavity, each year suggests strong site fidelity (USDA Forest Service 1994).
Molecular Biology and Genetics
Barcode data: Sphyrapicus nuchalis
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Sphyrapicus nuchalis
Public Records: 7
Specimens with Barcodes: 7
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N5B - Secure
Rounded National Status Rank: N5B,NNRN : N5B: Secure - Breeding, NNRN: Unranked - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Fairly large nesting range centered on the Rocky Mountains; large winter range extends from southwestern United States to central Mexico; large population size; apparently stable to increasing in most of range; threats include loss of aspen and cottonwood nesting habitat as a result of human activities and human-influenced processes.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Breeding Bird Survey (BBS) data for 1966-2007 for the Rocky Mountains suggest that populations are stable to increasing overall. Due to the localized and patchy nature of red-naped sapsucker habitat and the broad-scale design of BBS sampling, sample sizes are minimal for analysis for most states and physiographic regions.
Global Long Term Trend: Increase of 10-25% to decline of 30%
Comments: Extent of occurrence and area of occupancy probably have not changed more than 25% over the long term.
Degree of Threat: Medium
Comments: Threats are largely unknown. Dependence on aspen and mature riparian woodlands is cause for concern, however, as these habitats have been impacted by land management activities throughout the range. Loss of aspen stands and decline of aspen regeneration have occurred throughout the mountain west due to fire suppression, conifer invasion, cutting, and development. For example, quaking aspen has declined 50 to 95 percent in Yellowstone National Park's northern range, probably due to a complex web of factors that includes changes since the Park's establishment in natural fire regimes and the abundance of various mammals, such as beaver, elk, and wolves (Schullery 1995). In the Southwest, many aspen forests are now over 100 years old and declining in vigor. Due to fire suppression the stands are being overtopped by conifers and there is little aspen regeneration (Muldavin et al. 1999). Although decadent aspen may be beneficial in the short term, lack of regeneration obviously will adversely affect the species in the long term. Degradation and loss of mature cottonwood riparian forests due to cottonwood cutting, livestock grazing, alteration of stream hydrology, and other activities has also likely reduced habitat. Also see Tobalske (1992) for information on the effect of logging on abundance and reproductive success in Montana.
Restoration Potential: Still relatively abundant in appropriate habitats. Restoring and sustaining populations will require an ecological approach to management that incorporates a landscape perspective of the required habitat mosaic, the relationship to aspen (POPULUS spp.) and presence of shelf fungus (FOMES IGNIARIUS var. POPULINUS), and management to sustain and regenerate riparian and aspen woodlands.
Preserve Selection and Design Considerations: Apparently responds to a habitat mosaic that includes broad-leaved trees (e.g., aspen [POPULUS spp.], birch [BETULA spp.], cottonwood [POPULUS spp.]) for nesting and adjacent coniferous forest and/or willows (SALIX spp.) for foraging (Ehrlich and Daily 1988, Tobalske 1992, USDA Forest Service 1994). Known to use natural edges of mature mixed conifer and deciduous hardwood habitats (USDA Forest Service 1994). In one study, sapsuckers showed a significant correlation with stand area and the presence of adjacent hardwoods (Rosenberg and Raphael 1986). No significant sensitivity to patch size was observed in a study of Idaho cottonwood gallery forests, although birds were more often detected in large patches (more than 10-200 hectares; 0.21 birds per point count visit) than in small patches (less than 1-3 hectares; 0.12 birds per point count visit; Saab 1998).
Management Requirements: Sustaining populations requires maintaining, enhancing, and restoring snags, riparian woodlands, and hardwood stands of aspen (POPULUS spp.), birch (BETULA spp.), and cottonwood (POPULUS spp.) adjacent to coniferous forest.
FOREST MANAGEMENT: Both snags and live trees retained for the species should include a mix of hardwood and conifer species, particularly near riparian areas and mesic sites (USDA Forest Service 1994). Aspen and other trees with shelf fungus (FOMES IGNIARIUS var. POPULINUS) should be retained to provide optimal conditions for nest cavities. Access to conifer sap in adjacent forest is also important in the early spring, and to birches and aspens after bud-break (Tobalske 1992).
Thomas et al. (1979) estimated 25 centimeters was the minimum dbh required for a nest tree, and 4.6 meters the minimum cavity height. Nests have been reported in a wide range of tree sizes, from 9 to 47 centimeters dbh (Crockett and Hadow 1975, McClelland et al. 1979, Li and Martin 1991, Dobkin et al. 1995), with approximately 38 centimeter dbh the overall average.
Will use forest edges and logged forests, but extensive clearcuts or the removal of snags and preferred tree species would be detrimental. Also will use burns, partially-cut forests and small clearcuts where snags and live hardwood trees remain and adjacent forest is available for foraging (Bock and Lynch 1970, Tobalske 1992). In a western larch (LARIX OCCIDENTALIS) and Douglas-fir (PSEUDOTSUGA MENZIESII) forest in northwestern Montana, no significant difference in abundance or nest success was found between small partial cut and clearcut units (less than 16 hectares) and adjacent large tracts of unharvested even-aged forest. In cutting units, however, a large number of standing western larch snags and live paper birch (BETULA PAPYRIFERA) and aspen were retained (basal area of 1.8 to 8.0 square meters per hectare) and adjacent coniferous forest was available for feeding. The number of birch and aspen were equivalent in logged and unlogged stands, although canopy cover in logged stands was half that of unlogged stands (22 percent vs. 55 percent; Tobalske et al. 1991, Tobalske 1992). Assuming a linear relationship between sapsucker abundance and snag density, Bull (1978) recommended 150 snags greater than or equal to 25 centimeter dbh per 40 hectares to support maximum populations.
GRAZING: Mature riparian woodlands and regeneration of riparian trees have been heavily impacted by livestock throughout the West (Ohmart 1994). Grazing can have detrimental effects where the health and regeneration of aspen, cottonwood, and other preferred species is compromised. Studies of grazing impacts show mixed effects in the short term. In an Idaho cottonwood gallery forest where moderate to heavy grazing reduced understory shrub cover, Saab (1998) found no significant difference between grazed and unmanaged sites, although sapsucker abundances were slightly higher in unmanaged forest. Along one Colorado mountain stream, Schulz and Leninger (1991) observed sapsuckers only in grazed sites; however the authors indicated that aspen occurred in mesic upland areas but did not report the relationship between aspen cover and treatment. On a Nevada canyon stream, Medin and Clary (1991) found equal abundances in grazed and ungrazed sites, but the sites also showed no significant differences in percent forb cover, percent shrub cover, or in tree density.
On the other hand, in western Montana cottonwood/ponderosa pine (PINUS PONDEROSA) riparian habitat, were significantly more abundant on lightly grazed sites than on heavily grazed sites, where ground cover, bush cover, mid-canopy cover, and number of small trees (less than 10 centimeter dbh) were significantly reduced in the heavily grazed sites (Mosconi and Hutto 1982). In California/Nevada aspen habitat, Page et al. (1978, cited in Saab et al. 1995) also observed a negative response to grazing.
Management Research Needs: Management requirements have been little studied and there is ample opportunity to make significant contributions to the understanding of the species. Further study is needed of habitat relationships at multiple scales, and the effects of habitat alterations and management activities, particularly timber harvest, different grazing regimes, and fire. Better information is needed of nesting and foraging habitat relationships throughout the species range, and the species' relationship to the ecology and succession of hardwood and conifer woodlands. Landscape relationships, such as response to edge, fragmentation, patch size, and habitat juxtaposition are poorly known. Threats are largely unknown; regional assessments of the condition and trends in, aspen (POPULUS spp.), birch (BETULA spp.), and broad-leaved riparian cover types would help illuminate the threats to the species. Further understanding of interdependence of other species (e.g., shelf fungus) would provide an ecological perspective to management activities.
Biological Research Needs: Although this species is relatively common in appropriate habitats, its natural history has been little studied. Further research is needed on the distribution, migration, winter habitat use, and winter ecology. Its role as a keystone species deserves further study. Breeding biology, demographics, home range, territory size, site fidelity, dispersal, predators and competitors are poorly known.
Global Protection: Very many (>40) occurrences appropriately protected and managed
Relevance to Humans and Ecosystems
Stewardship Overview: Occurs in the inland West, inhabiting montane coniferous forests mixed with deciduous groves, particularly aspen (POPULUS TREMULOIDES), cottonwood (POPULUS spp.), paper birch (BETULA PAPYRIFERA), and willow (SALIX spp.). Sapsucker nests are strongly associated with the presence of shelf fungus (FOMES IGNIARIUS var. POPULINUS), which advances heart rot in aspen. Considered a keystone species because it creates nest cavities and sap wells that are used by other birds, mammals, and insects. Locally common, populations are apparently stable to increasing, but there is concern over loss of aspen and cottonwood nesting habitat and large snags for nest cavities.
Species Impact: May occasionally damage orchards (Phillips 1964).
The red-naped sapsucker is one of four North American woodpeckers in the genus Sphyrapicus. It has no subspecies. First described by Spencer Fullerton Baird in 1858, it was initially thought to be a subspecies of the yellow-bellied sapsucker. However, there are significant genetic differences between this species and the yellow-bellied sapsucker, and the American Ornithologists' Union recognized it as a distinct species in the seventh edition of its North American birds checklist, published in 1998. Genetic analysis has shown that the red-naped sapsucker is a sister species with (and very closely related to) the red-breasted sapsucker, and that these two species form a superspecies with the yellow-bellied sapsucker. All three species are known to hybridize with each other, with hybrids between red-naped and red-breasted sapsuckers proving particularly common.
The genus name Sphyrapicus is a combination of the Greek words sphura, meaning "hammer" and pikos, meaning "woodpecker". The specific name nuchalis is a modern Latin word meaning "of the nape". In its common name, "red-naped" refers to the red patch on the back of the bird's head, while "sapsucker" refers to its distinctive method of feeding.
The red-naped sapsucker is a medium-sized woodpecker, measuring 19–21 cm (7.5–8.3 in) long and weighing 32–66 g (1.1–2.3 oz). Adults have a black head with a red forehead, white stripes, and a red spot on the nape; they have a white lower belly and rump. They have a yellow breast and upper belly. They are black on the back and wings with white bars; they have a large white wing patch. Adult males have a red throat patch; for females, the lower part of the throat is red, the upper part white.
Habitat and range
Their breeding habitat is mixed forests in the Rocky Mountains and Great Basin areas of North America. They nest in a cavity in a dead tree. Other species which nest in tree cavities reuse nests formerly used by these birds.
To provide habitat and foraging for woodpeckers, forest management objectives on public land include snag and live tree retention. Numerous studies have shown woodpeckers will readily nest in logged areas as long as some stands are left standing. The drastic change in forest habitat cause by logging and tree retention drastically effects the quality of nesting sites and is detrimental to the red-naped sapsuckers habitat.
These birds migrate south and vacate areas at higher elevations.
True to their name, and like other sapsuckers, they drill holes in trees and eat the sap as well as insects attracted to it. They sometimes catch insects in flight; they also eat seeds and berries.
Red-naped sapsuckers typically lay 3–7 white eggs. The young are altricial, naked, and helpless. The eggs are incubated for 12–13 days and the young are able to fly and leave the nest after 25–29 days of hatching.
Throughout western North America, red-naped sapsucker (Sphyrapicus nuchalis) nests have been described primarily in trembling aspen (Populus tremuloides) with decay-softened wood. Heart-wood decay is reported to infect the roots of most aspens that red-naped sapsuckers choose to excavate for nesting. Red-naped sapsuckers typically excavate their first cavity relatively close to the ground and over subsequent years make progressively higher excavations. Most (68%) nest trees were live and 75% had broken tops. Western larch (Larix occidentalis) and birch were greatly over utilized compared to their availability.
- BirdLife International (2012). "Sphyrapicus nuchalis". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
- "ITIS Report: Sphyrapicus". Integrated Taxonomic Information System. Retrieved 1 May 2013.
- "ITIS Report: Sphyrapicus nuchalis". Integrated Taxonomic Information System. Retrieved 1 May 2013.
- Johnson, Ned K.; Zink, Robert M. (October 1983). "Speciation in Sapsuckers (Sphyrapicus): Genetic Differentiation". The Auk 100 (4): 871–884.
- "Red-naped Sapsucker (Sphyrapicus nuchalis)". Avibase: The World Bird Database. Retrieved 2 May 2013.
- Dunn, Jon L.; Alderfer, Jonathan (2011). National Geographic Field Guide to the Birds of North America (6 ed.). Washington, D. C., USA: National Geographic. p. 316. ISBN 978-1-4262-0828-7.
- Jobling (2010), p. 362.
- Jobling (2010), p. 276.
- Beedy, Edward C.; Pandolfino, Edward R. (2013). Birds of the Sierra Nevada: Their Natural History, Status and Distribution. Berkeley, CA, USA: University of California Press. p. 193. ISBN 978-0-520-27493-8.
- Kricher, John; Morrison, Gordon (1993). California and Pacific Northwest Forests. New York, NY, USA: Houghton Mifflin. p. 104. ISBN 978-0-395-92896-7.
- "All About Birds: Red-naped Sapsucker Identification". Cornell Lab of Ornithology. Retrieved 8 May 2013.
- "All About Birds: Red-naped Sapsucker Life History". Cornell Lab of Ornithology. Retrieved 8 May 2013.
- Tobalske, Bret (May 1992). "Evaluating habitat sustainability using relative abundance and fledging success of Red-naped Sapuckers". The Condor 94 (2): 550–553. doi:10.2307/1369234. Retrieved 5 December 2011.
- "Red-naped Sapsucker". Bird-Web. Retrieved 5 December 2011.
- Daily, Gretchen (December 1993). "Heartwood Decay and Vertical Distribution of Red-Naped Sapsucker Nest Cavities". The Wilson Bulletin 105 (4): pp. 674–679. Retrieved 4 December 2011.
- Jobling, James A. (2010). Helm Dictionary of Scientific Bird Names. London, UK: Christopher Helm. ISBN 978-1-4081-2501-4.
Names and Taxonomy
Comments: This species formerly was included with S. ruber in S. varius. Based on mating preference and effective reproductive isolation, S. ruber and S. nuchalis were regarded as distinct species by Johnson and Johnson (1985). Despite the near genetic identity of ruber and nuchalis based both on allozymes (Johnson and Zink 1983) and mtDNA sequences (Cicero and Johnson 1995), the latter authors cited the mating preference study as sufficient reason to regard the two taxa as distinct biologic species.