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Taxonomy Changes

TAXONOMIC CHANGES AND THE BBS DATABASE
Bruce Peterjohn and Greg Gough
 

Since the initiation of the North American Breeding Bird Survey (BBS) in 1966, a number of changes in the taxonomy of North American birds have been implemented by the American Ornithologists' Union (AOU). These changes have been described in the sixth and seventh editions of the check-list published by the AOU and the various supplements to these check-lists (see the literature cited section for the complete references to these publications). Much of the distributional information provided in this paper is derived from distributions described in these references.

The BBS has attempted to maintain a database that reflects these taxonomic changes. However, when two or more species have been lumped into a single species, the BBS usually maintains the former species as separate entities within the database. Hence, the lumping and re-splitting of some species during the history of the BBS has not affected how their data have been treated. When a single species has been split into two or more species, the ability to retroactively assign data to reflect the new classification is dependent upon the distribution of the new species. If their distributions are completely disjunct, the retroactive assignment of existing data does not pose a problem. However, should their distributions overlap, then it may not be possible to retroactively assign some data to either species.

This paper describes how the various taxonomic changes have been handled within the BBS database. All taxonomic changes that have occurred since 1966, including those mentioned in the 41st supplement, are discussed below. If only one form affected by a taxonomic change occurs within the area of coverage by the BBS, then that change is not included in this summary. For example, the changing taxonomy of the Green Heron (Butorides virescens)/Striated Heron (B. striatus) complex did not affect the BBS database since the latter species does not occur in North America. Based on the information provided below, users of BBS data should recognize the potential limitations of some data sets, especially for the analysis of population trends that may require use of data collected before and after a taxonomic change has been implemented.

Within this database, the BBS uses the numbering system of Sibley and Monroe (1990) to identify species. For species occurring in the United States and Canada, this system is identical to the numbering system formerly used by the AOU, except for a zero added at the beginning to make it a 5-digit number. Numbers for unidentified taxa are assigned by the BBS office; a complete list of species/taxa and their associated numbers is available elsewhere on this website [species list]. Since the AOU is no longer assigning numbers to new species, these numbers will be assigned by the BBS office in the future. Where these taxonomic changes produce a taxonomy consistent with Sibley and Monroe (1990), their numbers will be adopted.

Taxonomic changes will undoubtedly occur in the future, and this document will be updated as necessary to reflect these changes. When new distributional information is published that influences the treatment in the BBS database of a species group listed below, those changes will also be reflected through updates to this document.
 

Arctic Loon (Gavia arctica) and Pacific Loon (G. pacifica)

In North America, summering Arctic Loons (AOU number 00090) regularly occur only along the Seward Peninsula of Alaska (Kessel 1989). No BBS routes existed on this peninsula before 1993, hence, Arctic Loon would not have been reported from Alaskan BBS routes prior to the 1985 split of these loons. All pre-1985 reports of this species complex from Alaska were assigned to Pacific Loon (AOU number 00100). Three BBS routes were established in the vicinity of Nome on the Seward Peninsula in 1993, and Arctic Loon has been reported from one of these routes.
 

Western Grebe (Aechmophorus occidentalis) and Clark's Grebe (A. clarkii)

These grebes have widely sympatric breeding distributions. While Clark's Grebes (AOU number 00011) tend to be rare along the northern and eastern portions of this range, they may become equally common as Western Grebes (AOU number 00010) in other areas. Given their almost total sympatry, none of the BBS data could be retroactively assigned to either species within the BBS database. All BBS data collected before 1986 for this species complex were re-assigned to Aechmophorus sp. under AOU number 00012. Data from 1986 and subsequent years are assigned to either Western Grebe, Clark's Grebe, or Aechmophorus sp. as indicated by the BBS observers along individual routes. Hence, population trend estimates for these grebes based on BBS data are only valid for intervals beginning in 1986 or later years.
 

Great Blue Heron (Ardea herodias) and Great White Heron (A. h. occidentalis)

The Great White Heron has been retained as a separate form in the BBS database (AOU number 01920), even though it is currently considered a subspecies of the Great Blue Heron (AOU number 01940). "Würdemann's" Heron has never been recognized as a distinct form by the BBS; any reports of this intermediate form could have been included in the data for either Great Blue or Great White Heron.
 

Snow Goose and Blue Goose (Chen caerulescens)

The breeding distributions of both color morphs cover arctic regions that generally lie outside of the area of BBS coverage. There is one report of "Snow" Goose (AOU number 01690) from Alaska, while "Blue" Goose (AOU number 01691) is unrecorded from the BBS. Late migrants or non-breeders reported outside of their breeding range would not have been included in the BBS database.
 

Atlantic Brant (Branta bernicla hrota) and Black Brant (B. b. nigricans)

These forms have been retained separately in the BBS database (AOU numbers 01730 and 01740, respectively), even though they were lumped into a single species by the AOU. All reports from the BBS pertain to Black Brant found on routes in Alaska. Atlantic Brant breed in arctic regions outside of the area of BBS coverage, and reports of late migrants or non-breeders would have been excluded from the BBS database.
 

Green-winged Teal (Anas crecca carolinensis) and Common Teal (A. c. crecca)

The breeding distribution of Common Teal in North America is restricted to the eastern Aleutian Islands and Pribilof Islands of Alaska, areas where BBS routes have never existed. If Common Teal were reported from Alaskan BBS routes as non-breeders, these data probably would have been included in the data set for Green-winged Teal (AOU number 01390) because Common Teal is not recognized as a distinct form in the BBS database, or these reports may have been excluded altogether.
 

Mallard (Anas platyrhynchos) and Mexican Duck (A. p. diazi)

Mexican Ducks are currently considered a race of the Mallard, but are retained in the BBS database under AOU number 01331. Mexican Ducks freely hybridize with Mallards across their entire range in the southwestern United States, so very few "pure" Mexican Ducks may exist north of the Mexican border (Hubbard 1977). However, a few Mexican Ducks have been reported along BBS routes. Hence, any analysis of Mallard (AOU number 01320) population data from the southwestern states should also include the data for the Mexican Duck subspecies.
 

Red-tailed Hawk (Buteo jamaicensis) and Harlan's Hawk (B. j. harlani)

Harlan's Hawk is retained in the BBS database under AOU number 03380, although it is currently treated as a subspecies of the Red-tailed Hawk (AOU number 03370) by the AOU. Harlan's Hawks breed from Alaska and the Yukon Territory south into northern British Columbia and northwestern Alberta, but there are currently only three reports of this form in the BBS database within this range. However, some BBS reports of "Red-tailed Hawks" from the Yukon Territories and adjacent portions of Canada and Alaska may also pertain to the Harlan's race.
 

American Golden Plover (Pluvialis dominica) and Pacific Golden Plover (P. fulva)

Within the regular breeding range of Pacific Golden Plover (AOU number 02721) in western Alaska, BBS routes were initially established in the same year as this form was recognized as a distinct species by the AOU (1993). Hence, observers conducting these surveys have always specifically identified golden plovers reflecting the current taxonomy. If any extralimital Pacific Golden Plovers were encountered along other Alaskan BBS routes prior to 1993, these data would have been included in the data set for American Golden Plover (AOU number 02720).
 

Thayer's Gull (Larus thayeri) and Herring Gull (L. argentatus)

The arctic breeding distributions of Thayer's Gull (AOU number 00431) and the closely related Iceland Gull (L. glaucoides) (AOU number 00430) occur outside of the coverage of the BBS, and Thayer's Gull has never been reported from a BBS route. All reports of Herring Gull within the BBS database refer to the species as it is currently defined.
 

Eurasian Collared-Dove (Streptopelia decaocto) and Ringed Turtle-Dove (S. risoria)

These two species have always been kept separate in the BBS database, although the BBS has assigned the Sibley-Monroe number (22860) for the collared-dove. Before the mid-1980s, reports of both species within the BBS database may be problematical as a result of difficulties distinguishing these similarly appearing doves. Once the presence of the Eurasian Collared-Doves was positively established in Florida, BBS observers have more carefully distinguished these doves resulting in fewer identification problems. There are very few records of Ringed Turtle-Dove (AOU number 03152) from the BBS, of which the majority probably pertains to escapees rather than established populations. In contrast, Eurasian Collared-Doves are well established in the southeastern United States and their distribution is rapidly expanding across the country.
 

White-winged Parakeet (Brotogeris versicolurus) and Yellow-chevroned Parakeet (B. chiriri)

This taxonomic change was recognized by the AOU in 1997. Given the changing status of these introduced species in portions of southern Florida and southern California (Garrett 1997, Smith and Smith 1993), any data previously reported from BBS routes cannot be retroactively assigned to either species. Existing BBS data is limited to a single route in southern California, and will be assigned to an unidentified Brotogeris parakeet taxa (AOU number 03827). Canary-winged Parakeet will retain its existing AOU number (03825) while Yellow-chevroned Parakeet will be assigned the Sibley-Monroe number of 52021.
 

Eastern Screech-Owl (Otus asio) and Western Screech-Owl (O. kennicotti)

Neither species is very well sampled by the BBS, because they are very unlikely to be detected except by vocalizations and neither is very vocal immediately prior to sunrise when these surveys commence. Hence, there were very little data available for the entire screech-owl complex (AOU numbers 03730 and 03732, respectively) prior to the splitting of these species in 1983, and these reports were easily divided between the two species. None of the pre-1983 data were from the areas of sympatry. Since these species are readily identified by their vocalizations, data reported in 1983 and subsequent years have been separated by species even in areas where their ranges overlap.
 

Common Nighthawk (Chordeiles minor) and Antillean Nighthawk (C. gundlachii)

Antillean Nighthawks (AOU number 04201) have a very restricted breeding range in the U.S., where they are restricted to portions of the Florida Keys. There are very few BBS routes located within this range, and these routes have not been consistently surveyed in recent years. After being recognized as a distinct species in 1983, Antillean Nighthawks have been reported only once from one of the routes situated on the keys. Hence, pre-1983 data for Common Nighthawks (AOU number 04200) from these Florida Keys BBS routes could include a very small number of reports of Antillean Nighthawks.
 

Yellow-bellied Sapsucker (Sphyrapicus varius), Red-naped Sapsucker (S. nuchalis), and Red-breasted Sapsucker (S. ruber)

This complex was split into three separate species between 1983 and 1985. Limited sympatry exists within this complex, primarily in the northern Rocky Mountains of Alberta for Yellow-bellied (AOU number 04020) and Red-naped (AOU number 04021) sapsuckers, and actually or potentially along portions of the Sierra Nevada and Cascade mountains of California, Oregon, and Washington for Red-breasted (AOU number 04030) and Red-naped sapsuckers.

The BBS data collected before 1983-1985 were retroactively assigned between these three species during 1992. This assignment was routine in areas of allopatry. Such assignments were more difficult in and near regions of sympatry, although data collected along routes between 1985 and 1991 proved to be very helpful in making these assignments. Where only one species of sapsucker had been reported along a route after the taxonomic changes, all of the previous data were also assigned to that species. Using this system, the sapsucker data for most routes located in or near regions of sympatry could be assigned to individual species. Such assignments were not possible on routes where both species occur, and the earlier reports were treated as unidentified sapsuckers (AOU number 04022). This problem was most prevalent in Oregon and Washington, where data on 15 and 7 routes, respectively, could not be retroactively assigned to either sapsucker species. Hence, BBS data and trend estimates obtained from areas of sympatry should be used with caution for this species complex, since some routes will only have identifications to species after the 1983-1985 taxonomic changes.

Unidentified sapsuckers are still reported by BBS observers on routes located in areas of sympatry, especially for birds that are heard but not seen. Within the breeding distribution of Williamson's Sapsucker (S. thyroideus), however, this classification may be also used for any sapsucker that could not be positively identified to species.
 

Northern Flicker (Colaptes auratus) and Gilded Flicker (C. chrysoides)

Despite the various taxonomic changes that have occurred within this species complex after 1966, the BBS has always treated Yellow-shafted (AOU number 04120), Red-shafted (AOU number 04130), and Gilded flickers (AOU number 04140) as distinct taxa within the database. An unidentified flicker category also exists (AOU number 04123), and is used in the large region of sympatry between Yellow-shafted and Red-shafted flickers on the Great Plains and the much smaller region of sympatry between Gilded and Red-shafted Flickers in the southwestern U.S.

BBS data from regions of sympatry should be viewed with considerable caution. Many observers identify all flickers to specific taxa on their routes, and it is not unusual for one observer to report only Yellow-shafteds from a Great Plains BBS route while another observer reports only Red-shafteds from the same route. There is also variability in the use of the unidentified flicker category from state to state. For example, there is only one record of an unidentified flicker from Kansas but more than 30 from Nebraska. From the Great Plains and other regions of sympatry, combining all flicker data (including unidentified reports) for use in trend estimates may be more reasonable than trends derived from the individual taxa.
 

Alder Flycatcher (Empidonax alnorum) and Willow Flycatcher (E.traillii)

Before 1974, all reports for this complex were recorded as "Traill's" Flycatcher. After the taxonomic change in 1973, the BBS has recognized both Alder (AOU number 04661) and Willow flycatchers (AOU number 04660), as well as unidentified members of this complex ("Traill's" Flycatcher with AOU number 04665) within the database.

The retroactive assignment of data collected between 1966-1973 has taken place during the 1990s. Assigning data in regions of allopatry was routine. However, a broad region of sympatry exists across the northern U.S. and southern Canada, and retroactively assigning data in this region was considerably more difficult. In portions of this region of sympatry, one of these species is quite rare while the other is fairly numerous. Using breeding bird atlases and other sources of distributional information, as well as the data collected along BBS routes between 1974 and 1990, the retroactive assignment of data were possible for many routes where one of these species is a rare summer resident. However, in areas where both species are numerous and regularly recorded on BBS routes, retroactive assignments were not possible and the 1966-1973 data were retained within the unidentified "Traill's" Flycatcher category.

Caution should be exercised when using BBS data for estimating population trends for these species. In regions of sympatry, trend estimates may be valid only for intervals beginning in 1974 or subsequent years. An examination of the data set is necessary to determine the amount of the pre-1974 data assigned to the unidentified "Traill's" Flycatcher taxa, and will indicate if 1973 or earlier years should be incorporated into the trend analysis.
 

Cordilleran Flycatcher (Empidonax occidentalis) and Pacific-slope Flycatcher (E. difficilis)

Following the splitting of the Western Flycatcher complex in 1989, the BBS has used Cordilleran Flycatcher (AOU number 04640), Pacific-slope Flycatcher (AOU number 04641), and unidentified "Western" Flycatcher complex (AOU number 04642) within the database. The retroactive assignment of 1966-1989 data within areas of allopatry was routine. However, the assignment of 1966-1989 data within areas of sympatry can only be considered provisional at this time. Recent field work indicates this area of sympatry is much larger than previously known, especially east of the Cascade Mountains in Oregon, Washington, and southern British Columbia. Pacific-slope Flycatchers are more widely distributed in this region, and flycatchers with intermediate song-types have also been reported. Additional field work will be required before the actual status of both species within this region can be established. The BBS office welcomes any information that can be provided to better elucidate the status of these species in the Pacific Northwest region.

Estimation of population trends for individual species within the region of sympatry is not recommended at this time, although estimation of trends for the entire "Western" Flycatcher complex would still be possible. The data sets for these taxa will likely undergo modifications in the future as better distributional information becomes available.
 

Couch's Kingbird (Tyrannus couchii) and Tropical Kingbird (T. melancholicus)

When these two species were recognized as distinct in 1983, they had very disjunct distributions in the southern U.S. Couch's Kingbirds (AOU number 04461) were restricted to the lower Rio Grande valley area of south Texas, while breeding Tropical Kingbirds (AOU number 04460) were found only in southeastern Arizona. The retroactive assignment of all data within this species complex did not pose any problems for the BBS. While small numbers of Tropical Kingbirds have recently been discovered in south Texas, they have not yet been reported from any of the BBS routes in that area.
 

Blue-headed Vireo (Vireo solitarius), Cassin's Vireo (V. cassinii), and Plumbeous Vireo (V. plumbeus)

The "Solitary" Vireo complex was split into three species in 1997, and the BBS database has been recently updated to reflect the current taxonomy. The Blue-headed Vireo retains AOU number 06290, Cassin's Vireo becomes AOU number 06291, and Plumbeous Vireo is AOU number 06292, while an unidentified "Solitary" Vireo category is assigned AOU number 06295.

The breeding distributions of these three vireos are largely allopatric, and the retroactive assignment of BBS data was routine across most of their ranges. However, some regions of actual or potential sympatry exist and data from these regions were assigned to the unidentified category. Blue-headed and Cassin's vireos are known to be sympatric in portions of central Alberta (Semenchuk 1992), where some hybridization occurs. This zone of sympatry is not well defined at this time, and could be more extensive than has been documented to date. The ranges of Plumbeous and Cassin's vireos are close to overlapping in portions of eastern California. Since Plumbeous Vireos are apparently expanding their distribution westward in the state, several small zones of sympatry may currently exist or eventually develop. Hence, the treatment of data for this species complex within the BBS database should be viewed as tentative pending the receipt of better distributional information for these newly recognized species.
 

Red-eyed Vireo (Vireo olivaceus) and Yellow-green Vireo (V. flavoviridis)

Despite the various taxonomic treatments of these forms since 1966, the BBS has always maintained them as distinct taxa within the database (AOU numbers 06240 and 06250, respectively). Their breeding distributions are normally allopatric, so an unidentified vireo category is not necessary for this species complex. Yellow-green Vireos have become very rare summer residents within the lower Rio Grande valley of southern Texas in recent years, and have never been recorded along BBS routes.
 

Western Scrub-Jay (Aphelocoma californica), Florida Scrub-Jay (A. coerulescens), and Island Scrub-Jay (A. insularis)

These species exist in the BBS database under AOU numbers 04810, 04790, and 04811, respectively. All three species have allopatric distributions, so the retroactive assignment of all BBS data for this complex did not pose any problems. Note that a BBS route exists on Santa Cruz Island, California (it has been surveyed only once), so there is very limited data for the Island Scrub-Jay in the BBS database.
 

Oak Titmouse (Beolophus inornatus) and Juniper Titmouse (B. ridgwayi)

The "Plain" Titmouse was split into these two species in 1997, and the BBS database has been recently updated to reflect the new taxonomy. Oak Titmouse retains AOU number 07330, and Juniper Titmouse is assigned AOU number 07331. An unidentified "Plain" Titmouse taxa will be assigned AOU number 07332, if such a category is necessary.

The breeding distributions of these two species are largely allopatric, and the retroactive assignment of data from most of their ranges is straightforward. Sympatric distributions are restricted to a small area in northwestern California (Cicero 1996). None of the existing BBS routes are located within this region of sympatry. However, we view the current assignment of data as preliminary, because additional field work could expand the known area of overlap and cause the BBS office to re-examine how these data have been assigned.
 

Tufted Titmouse (Beolophus bicolor) and "Black-crested" Titmouse (B. b. atricristatus)

The "Black-crested" Titmouse has been retained as a distinct taxa (AOU number 07320) in the BBS database, while Tufted Titmouse retains AOU number 07310. These two forms hybridize freely where their distributions overlap in east-central Texas, where unidentified titmice (AOU number 07315) have very infrequently been reported from BBS routes. There is a tendency for observers to specifically identify all titmice detected on routes located in or near this hybrid zone. Analyses of Tufted Titmouse trends for Texas, as this species is currently defined, should utilize data from all three categories.
 

Bushtit (Psaltriparus minimus) and "Black-eared" Bushtit (P. m. melanotis)

The "Black-eared" Bushtit has a distribution restricted to southwestern New Mexico and adjacent western Texas, and had never been recorded from BBS routes when this form was merged with Bushtit (AOU number 07430) in 1973. No AOU number has ever been assigned to "Black-eared" Bushtit in the BBS database. Subsequent to 1973, any reports of "Black-eared" Bushtits from BBS routes would have been included in the database for Bushtit.
 

House Wren (Troglodytes aedon) and "Brown-throated" Wren (T. a. brunneicollis)

No "Brown-throated" Wrens had been recorded from BBS routes when this form was merged with House Wrens (AOU number 07210) in 1983, reflecting an absence of routes within the mountain ranges of southeastern Arizona where this form breeds in the United States. Hence, "Brown-throated" Wren had not been assigned an AOU number within the BBS database. Additional BBS routes have been added in Arizona during the 1990s. "Brown-throated" Wrens could be reported on a few of these routes, but these data are included within the database for House Wren.
 

Black-tailed Gnatcatcher (Polioptila melanura) and California Gnatcatcher (P. californica)

These gnatcatchers are recognized in the BBS database by AOU numbers 07520 and 07530, respectively. These species have allopatric distributions in the U.S., and no BBS routes are located in the portion of southern California where their ranges are in close proximity. Hence, all existing data was retroactively assigned to each species within the BBS database following the taxonomic change in 1989.
 

Gray-cheeked Thrush (Catharus minimus) and Bicknell's Thrush (C. bicknelli)

Both species are very poorly sampled by the BBS. The few reports of Gray-cheeked Thrush (AOU number 07570) from BBS routes are from the boreal forest regions of Alaska, northern Canada, and Newfoundland, well removed from the breeding distribution of Bicknell's Thrush (AOU number 07571) in northern New England and adjacent southeastern Canada. Following recognition of Bicknell's Thrush as a distinct species in 1995, all existing data in the BBS database could be retroactively assigned to these species. At this time, a category for unidentified members of this species complex has not been necessary for BBS data.
 

White Wagtail (Motacilla alba) and Black-backed Wagtail (M. lugens)

The BBS was initiated in Alaska in the same year that these two species were recognized as distinct (1983). Hence, all BBS data have been collected under the current taxonomy. Only White Wagtails (AOU number 06940) regularly nest in the state and have been reported from one BBS route located on the Seward Peninsula. Black-backed Wagtail (AOU number 06951) is a sporadic breeder in western Alaska and is currently unrecorded from the BBS.
 

"Myrtle" Warbler (Dendroica coronata coronata) and "Audubon's" Warbler (D. c. auduboni)

Within the BBS database, these forms have been retained as distinct taxa even though they were merged to form the Yellow-rumped Warbler in 1973. They are assigned AOU numbers 06550 and 06560, respectively. In the hybrid zone that extends from southeastern Alaska across central British Columbia to southern Alberta, AOU number 06556 is used for warblers that cannot be assigned to either taxa. Relatively few BBS routes currently exist within this hybrid zone, and most reports of unidentified Yellow-rumped Warblers have been from routes in southeastern Alaska. The relatively small amount of data assigned to the unidentified category would have little influence on most regional trend estimates for these taxa, except in southeastern Alaska.
 

Canyon Towhee (Pipilo fuscus) and California Towhee (P. crissalis)

These species are assigned AOU numbers 05910 and 05911, respectively, in the BBS database. Their breeding distributions are entirely allopatric, so the retroactive assignment of BBS data between these species was accomplished easily.
 

Eastern Towhee (Pipilo erythrophthalmus) and Spotted Towhee (P. maculatus)

In the BBS database, Eastern Towhee is assigned AOU number 05870, Spotted Towhee is AOU number 05880, and unidentified towhees are AOU number 05871. These two species have largely allopatric distributions where the retroactive assignment of data was routine following the taxonomic change in 1995. Their breeding ranges potentially or actually overlap on the north-central Great Plains along a zone extending from central Nebraska north to southern Saskatchewan. Within this range of sympatry, all BBS data for this species complex obtained before 1996 is currently assigned to the unidentified towhee category. Since these two towhees have distinctly different vocalizations, they should be readily separated by BBS observers. Future reports may allow for the retroactive assignment of data along some routes in this region of sympatry. However, such assignments have not been attempted at this time.

The zone of sympatry between these two species is not well defined in some states. As better distributional information becomes available, this zone could expand or contract. Additional changes to the BBS database may be necessary as better information becomes available. Given this uncertainty, data from the states and province where sympatry occurs should be used cautiously in the estimation of BBS population trends for these towhees, because some routes will only have identifications to species after 1995.
 

Savannah Sparrow (Passerculus sandwichensis) and "Ipswich" Sparrow (P. s. princeps)

"Ipswich" Sparrow has a very restricted breeding distribution limited to Cape Sable Island and the adjacent mainland of Nova Scotia, and was not reported from BBS routes before 1973 when this form became conspecific with the Savannah Sparrow (AOU number 05420). At that time, no AOU number had been assigned to "Ipswich" Sparrow within the BBS database. If any "Ipswich" Sparrows have been reported from Nova Scotia BBS routes subsequent to 1973, these data would appear as Savannah Sparrow in the database.
 

Saltmarsh Sharp-tailed Sparrow (Ammodramus caudacutus) and Nelson's Sharp-tailed Sparrow (A. nelsoni)

As this species complex is currently defined, these two species have a very small region of sympatry in southern Maine, an area where there are no BBS routes located within the salt marsh habitats preferred by these sparrows. All BBS data for this species complex were obtained from regions of allopatry, and the retroactive assignment between these two species was routine. The BBS uses AOU numbers 05490 and 05491, respectively. No category currently exists for unidentified sharp-tailed sparrows, but may be necessary should BBS routes become established within the region of sympatry.
 

Seaside Sparrow (Ammodramus maritimus), "Dusky" Seaside Sparrow (A. m. nigrescens), and "Cape Sable" Seaside Sparrow (A. m. mirabilis)

Neither "Dusky" nor "Cape Sable" seaside sparrows had been reported from BBS routes before 1973 when both became conspecific with the Seaside Sparrow (AOU number 05500). Both forms had very restricted distributions in Florida, and neither had an AOU number assigned to them within the BBS database. The "Dusky" Seaside Sparrow is now extinct. Post-1973 Seaside Sparrow data from one BBS route in southern Florida probably pertains to the "Cape Sable" race, and several routes located within Everglades National Park could potentially produce reports of this race. All other BBS data from Florida are referable to the maritimus group of the Seaside Sparrow.
 

"Dark-eyed" Junco (Junco hyemalis) complex

Despite the various taxonomic treatments of this complex by the AOU, the recognizable forms of Dark-eyed Junco have always been recognized as distinct taxa in the BBS database. These forms are Slate-colored Junco (AOU number 05670), Oregon Junco (AOU number 05671), Gray-headed Junco (AOU number 05690), White-winged Junco (AOU number 05660), and Pink-sided Junco (AOU number 05680). Additionally, an unidentified junco category has AOU number 05677.

Varying degrees of intergradation occur between these taxa, and the field identification of some individuals may be difficult. Despite these identification problems, most reports from BBS routes have been identified to specific taxa, even in areas of sympatry. Hence, BBS data for these taxa should be viewed cautiously. In some areas, combining the data from two taxa and the unidentified category may provide the most appropriate data set for analysis of population trends.
 

Great-tailed Grackle (Quiscalus mexicanus) and Boat-tailed Grackle (Q. major)

The BBS assigned AOU numbers 05130 to Boat-tailed Grackle and 05120 to Great-tailed Grackle. AOU number 05135 was created for unidentified Boat-tailed/Great-tailed grackles when data for this species complex were updated in the 1990s.

The breeding ranges of both species are largely allopatric, although they become sympatric in southwestern Louisiana and adjacent southeastern Texas. The retroactive assignment of the 1966-1973 data was routine within areas of allopatry. Post-1974 data were used to indicate the presence of these grackles on BBS routes within the region of sympatry. On most routes, only a single species within the complex has been reported and the earlier data were also assigned to that species. For the very small number of routes, both grackles are present and the 1966-1973 data were assigned to the unidentified category. Hence, trend estimates from routes within this small region of sympatry should be viewed with caution but should have little influence on the broader regional trends produced for these species.
 

Baltimore Oriole (Icterus galbula) and Bullock's Oriole (I. bullockii)

These taxa have always been retained as distinct forms in the BBS database since 1966, even though they were considered conspecific for more than 20 years. They are assigned AOU numbers 05070 and 05080, respectively, while unidentified orioles are assigned AOU number 05077. These species regularly hybridize along the central Great Plains in a zone extending southward from the Dakotas, and use of the unidentified oriole category is encouraged within this hybrid zone. However, most observers tend to identify all orioles to species that are detected on their routes, even those located within the hybrid zone, and the unidentified category has been regularly used only in Oklahoma. Hence, data from the central Great Plains for both orioles should be used cautiously for the analysis of population trends.
 

Gray-crowned Rosy-Finch (Leucosticte arctoa), Black Rosy-Finch (L. atrata), and Brown-capped Rosy-Finch (L. australis)

These forms have always been maintained as distinct taxa in the BBS database, despite the varying taxonomic treatment accorded by the AOU. They are assigned AOU numbers 05240, 05250, and 05260, respectively. Unidentified rosy-finches are assigned AOU number 05241, for use in regions of sympatry between Gray-crowned and Black rosy-finches. Given their specialized breeding habitats, at very high elevations or at high latitudes, all species of rosy-finch are very poorly represented within the BBS database.
 
 

LITERATURE CITED

American Ornithologists' Union. 1973. Thirty-second supplement to the American Ornithologists' Union check-list of North American birds. Auk 90:411-419.

_______. 1976. Thirty-third supplement to the American Ornithologists' Union check-list of North American birds. Auk 93:875-879.

_______. 1983. The A.O.U. check-list of North American birds, sixth ed. American Ornithologists' Union. 877p.

_______. 1985. Thirty-fifth supplement to the American Ornithologists' Union check-list of North American birds. Auk 102: 680-686.

_______. 1987. Thirty-sixth supplement to the American Ornithologists' Union check-list of North American birds. Auk 104:591-596.

_______. 1989. Thirty-seventh supplement to the American Ornithologists' Union check-list of North American birds. Auk 106:532-538.

_______. 1991. Thirty-eighth supplement to the American Ornithologists' Union check-list of North American birds. Auk 108:750-754.

_______. 1993. Thirty-ninth supplement to the American Ornithologists' Union check-list of North American birds. Auk 110:675-682.

_______. 1995. Fortieth supplement to the American Ornithologists' Union check-list of North

America birds. Auk 112:819-830.

_______. 1997. Forty-first supplement to the American Ornithologists' Union check-list of North American birds. Auk 114:542-552.

_______. 1998. The A.O.U. check-list of North American birds, seventh ed. American Ornithologists' Union. 829 p.

Cicero, C. 1996. Sibling species of titmice in the Parus inornatus complex (Aves: Paridae). Contr. Univ. Cal. Berkeley Mus. Vert. Zool. No. 128.

Garrett, K. L. 1997. Population status and distribution of naturalized parrots in southern California. Western Birds 28: 181-195.

Hubbard, J. P. 1977. The biological and taxonomic status of the Mexican Duck. Bulletin of New Mexico Dept. Game and Fish No. 16.

Kessel, B. 1989. Birds of the Seward Peninsula, Alaska. Univ. of Alaska Press, Fairbanks. 330p.

Semenchuk, G. P. 1992. The atlas of breeding birds of Alberta. Federation of Alberta Naturalists, Edmonton, AB. 391p.

Sibley, C.G., and B.L. Monroe, Jr. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, CT. 1111p.

Smith, P. W., and S. A. Smith. 1993. The exotic dilemma for birders: The Canary-winged Parakeet. Birding 25: 426-430.



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