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Status and Trends of Terrestrial Vertebrate Species

Conservation Status Ranks for Southern Species

The databases of the State Natural Heritage agencies were used to derive a regional species list of global conservation ranks. The global (G) ranks reflect a species’ rarity throughout its range. For example, a species holding the global conservation ranking of G1 in Virginia also carries the same rank elsewhere in the nation.

These ranks are: GX (presumed extinct: intensive search has not located additional populations); GH (possibly extinct: historically known and may be rediscovered); G1 (critically imperiled globally because of extreme rarity (observations include five or less locations or less than 1,000 animals) or because some factor of its biology makes it vulnerable to extinction); G2 (imperiled globally because of rarity (observations reflect 6-20 locations or 1,000-3,000 animals) or because of other factors making it vulnerable to extinction); G3 (vulnerable globally because of rarity throughout its range (observations include 21-100 locations or 3,000-10,000 animals) or because it is found locally in a restricted area); G4 (apparently secure globally, although the species may be rare in parts of its range, especially at the periphery;. usually more than 100 occurrences and 10,000 individuals); and G5 (secure globally: observations are common and widespread).

Figure 1 shows the proportion of vertebrate taxa in each of the conservation ranking categories. One hundred and thirty two species are considered to be of conservation concern. Among terrestrial vertebrates, 28 species are classified as critically imperiled, 37 species as imperiled, and 67 species as vulnerable. Eighty-six percent of southern terrestrial vertebrate species are designated as relatively secure by Natural Heritage.

Figure 2 shows species ranked as presumed or possibly extinct, critically imperiled, imperiled, or vulnerable among the four major vertebrate taxa. Collectively, these species represent animals with elevated risks of extinction or of conservation concern.

The proportion of species at risk varies greatly among taxonomic groups. Forty-one percent of imperiled species are amphibians, followed by reptiles (30 percent), birds (15 percent), and mammals (14 percent). With the exception of mammals, the number of species at risk within each taxonomic group is not proportionate with their respective richness in the region. For example, amphibian species comprise only 14 percent of the terrestrial vertebrates occurring in the South. Yet they comprise 41 percent of the imperiled species list. Conversely, bird species comprise 48 percent of southern terrestrial vertebrates, but only 15 percent of the imperiled species. Refer to Chapter TERRA-5 for additional data on regional species richness.

The conservation statuses of individual species are presented in Table 3, Table 4, Table 5 and Table 6. Several of these species are discussed in further detail in Chapter AQUA-5 and Chapter TERRA-5, including the factors influencing imperilment and species habitat relationships. Species that are Federally listed as threatened or endangered are discussed in Chapter TERRA-5.

Fifty-four amphibian species are of conservation concern (Table 3). Salamanders dominate with 51 listings; frogs and toads have 3 listings. Examples include the Houston toad, gopher frog, flatwoods salamander, Ocoee salamander, green salamander, and several species in the Plethodon, Desmognathus, and Eurycea genera.

Forty reptile species are imperiled or vulnerable (Table 4). Reptile subgroups with global rankings of concern include turtles (19), lizards (10), snakes (9), and others (2). Oceanic and map turtles dominate this list. Other reptiles of conservation concern include the alligator snapping turtle, bog turtle, gopher tortoise, glass lizard, southern hognose snake, and crocodile.

Twenty avian species are of concern (Table 5). Subtaxa include 2 wading birds, 3 shorebirds, 6 perching birds, and 9 others. Several of these species include the whooping crane, piping plover, Bachman's sparrow, Florida scrub jay, red-cockaded woodpecker, and lesser prairie chicken.

Eighteen mammal species are imperiled or vulnerable (Table 6). Mammalian subtaxa with global rankings of concern include 5 bats 8 rodents 3 carnivores, and 2 others. Bats are represented by the Indiana bat, Rafinesque's big-eared bat, southeastern myotis, and several other species. Additional mammals include the Allegheny woodrat, red wolf, and swift fox.

Population and Harvest Trends for Southern Species

The regional population and harvest trends presented in this section, unless otherwise stated, originated from the RPA (Flather and others 1999). The RPA represented the best source of quantitative data on regional trends for multiple species at the time of this Assessment. Information was collected from cooperating State wildlife agencies. Population estimates were summed across those States that provided data. (The list of States that provided population estimates is available at the Rocky Mountain Research Station, Fort Collins, Colorado). The absence of data from certain States resulted from variation in the distribution of species or the lack of data for certain years. The RPA included only States that provided estimates for 1975 to 1990 (in 5-year intervals), and 1993 in the trend analysis.

Projections were based on a weighted average percentage change from 1993 to the year 2000 and 2045 for States that provided projection estimates. The average percentage change was then applied to the 1993 population estimate in order to extrapolate a total projected population for States that provided population estimates (Flather and others 1999).

Big Game Species. Big game species are primarily large mammals taken for sport or subsistence. Because of State agency convention, the wild turkey also is included. The species comprising big game were the first to stimulate widespread public interest in wildlife conservation. For this reason, historical information about game species is extensive for several States.

Wild turkey populations have consistently increased since 1975 (Figure 3). Five States project that turkey populations will decline over the next four decades (Flather and others 1999).

For States reporting on white-tailed deer, populations have increased approximately four-fold since 1975 (Figure 4). There is concern among State personnel that deer may become a management problem during the next decade. Seven States expect deer numbers to decline slightly over the next 50 years (Flather and others 1999). (Additional information on deer is provided in Chapter TERRA-3, Chapter TERRA-4, and Chapter TERRA-5).

The trend in black bear numbers is positive for the four States reporting (Figure 5). Biologists from these States expect bear populations to decline somewhat over the next few decades (Flather and others 1999). (Note: The Florida and Louisiana subspecies of black bear, of conservation concern in the region, are discussed separately in Chapter TERRA-5).

Small Game Species. Species classified as small game typically include resident game birds and mammals that are associated with upland (forest, range, or agricultural) habitats. There is some variation among State wildlife agencies as to which species are managed as small game. In this Chapter, quail, grouse, rabbits, and squirrels are considered small game. Few State wildlife agencies monitor small game populations; therefore, the trends reviewed here should be interpreted carefully.

The populations of gray, red, and fox squirrels have been declining in the South since 1985 (Figure 6). Cottontail rabbit populations declined slightly between 1975 and 1980 (Figure 7), but recovered by 1990. One State projects that cottontail rabbit populations may decline by 2045 (Flather and others 1999).

Northern bobwhite quail populations have declined from 1975 to the present (Figure 8). Among the States reporting trends in bobwhite abundance, populations have declined by nearly 50 percent, from 23 million birds in 1975 to 12 million birds in 1993 (Flather and others 1999). Forest (ruffed) grouse populations show a cyclical pattern, but appear to have declined since 1985 (Figure 9).

Bobwhite quail trends from the Breeding Bird Survey (BBS) are consistent with State agency estimates (Flather and others 1999). BBS data suggest that the abundance of this species has declined significantly (P < 0.05) in the South. Bobwhite numbers have declined by 2.6 percent per year from 1966 to 1996, and have declined at an even greater rate since 1985 (5.6 percent per year).

State agency projections for most small game species suggest minor changes in future population status. Forest grouse are expected to remain stable. State biologists forecast declines for bobwhite quail, squirrels, and cottontails.

Migratory Game Birds. Migratory game birds include waterfowl, such as ducks and geese, and other migratory species, such as mourning doves and woodcock. The long history of migratory bird management in North America has resulted in an impressive monitoring system. Population and harvest trends originate from annual reports published by the U.S. Fish and Wildlife Service and the North American Waterfowl Plan (Flather and others 1999).

Waterfowl trends are traditionally tracked by major flyways, which are the migration routes from breeding to wintering habitat. In the South, the major routes are the Atlantic and Mississippi flyways (Figure 10). National duck harvests have been recorded since the early 1960s.

Over the last 25 years, 41 percent of the national harvest was taken in the Mississippi flyway and 15 percent from the Atlantic flyway. Both had large harvests during the 1970s, followed by substantial declines through much of the 1980s, and substantial harvest increases during the 1990s. Duck harvests in the Mississippi flyway increased by 260 percent from 1988 to 1995, with a record 6.6 million ducks harvested in 1995 (Flather and others 1999).

Trends in goose abundance were derived from surveys conducted in migration and wintering areas. Record numbers of geese were harvested for three consecutive years starting in 1993 along the Mississippi flyway (Figure 11). After reaching a peak harvest of about 550,000 birds in 1983, the goose harvest in the Atlantic flyway declined to nearly 180,000 birds in 1995.

Management units are traditionally used by agencies to report population trends of mourning doves and American woodcock. Both species are monitored using call-count surveys, which provide an index of population size. National trends in population indices for both species show evidence of declines, but the magnitude of the decline is greater for woodcock than for mourning doves. This pattern is confirmed by Breeding Bird Survey data, which indicate that doves declined annually at a rate of 0.3 percent compared to a 3.2 percent decline for woodcock over the 30-year period (Flather and others 1999).

Mourning dove calling counts indicate declining populations during the last 10 years in the Eastern and Central Management Units (Figure 12). Intensive agricultural practices may be influencing the breeding populations throughout much of the bird’s range (Brady and others 1998). The acreage of agricultural land in the Eastern Management Unit is positively related to dove populations because agricultural fields provide the forest edge habitat preferred by doves. Increased herbicide use and crop rotation may have contributed to observed declines (Martin and Sauer 1993). In the Central Management Unit, the trend toward fewer and larger farms also may have influenced dove populations.

Call-count trends for woodcock show similar declines in both the Eastern and Central Management Units (Figure 13). Trends since 1968 indicate that the number of woodcock heard have declined by 2.5 percent per year in the Eastern Unit and 1.6 percent per year in the Central Unit (Flather and others 1999). In the last decade, this rate of decline has accelerated. Woodcock select early successional hardwood forests interspersed with fields and forest openings. As with the mourning dove, the widespread decline in woodcock may be linked with habitat alteration due to forest succession and land use intensification (Straw and others 1994).

Furbearer Species. There are few comprehensive examinations of trends in furbearer populations nationwide. Often, the only available data are temporal harvest trends that reflect fur prices rather than population status. The limited information on population trends makes furbearer projections uncertain.

The RPA used a compilation of furbearer status reports completed for the International Association of Fish and Wildlife Agencies during 1993. A survey of State agency biologists provided population projections to 2003. (Southwick Associates 1993).

Population projections of southern furbearers are shown in Figure 14, Figure 15, Figure 16, Figure 17, Figure 18 and Figure 19. Of the 10 Southern States reporting beaver population projections, five expected population increases through 2003 (Figure 14). The beaver population is projected to decline in North Carolina, and remain stable (or increase) in the remainder of the South.

The majority of raccoon populations are projected to increase or remain stable throughout the South (Figure 15). Exceptions occur in Alabama and North Carolina, where disease-caused declines are projected (Flather and others 1999).

Of the four States reporting on muskrat populations, two expect population increases through 2003 (Figure 16). The remaining States (Virginia and Tennessee) project stable populations. Projections on coyote abundance are limited to Georgia and Mississippi (Figure 17). Both States report that coyote populations are expected to remain stable.

Bobcat projections are reported only for Florida and Oklahoma (Figure 18). Florida biologists report stable bobcat populations, while Oklahoma biologists report that bobcat populations are increasing. Finally, the five States that made projections for red and gray foxes (Virginia, Kentucky, Tennessee, South Carolina, and Texas) predicted stable populations (Figure 19).

Nongame Birds. In the United States, nongame birds are not legally taken for sport, subsistence, or profit. Nongame species comprise the majority of taxa that inhabit the South. There are few data sources on populations of nongame species.

Data from the BBS were used to provide information on breeding bird trends in the South for the RPA. Details on the implementation of the BBS can be found in Droege (1990); information on statistical analyses can be found in Sauer and others (1997). The relative abundance trend for each bird species was summarized in two ways. First, the numbers of species with statistically significant increasing, decreasing, or stable trends were estimated. Second, birds were grouped according to life-history characteristics including nest type (cavity or open cup), nest location (ground, low, midstory or canopy), migration status (neotropical migrant, short-distance migrant, permanent resident), and breeding habitat (woodland, shrubland, grassland, wetland, urban). The resulting trends are presented in Figure 20.

Approximately 42.4 percent of breeding bird species appear stable, 35.2 percent have declined, and 22.4 percent have increased across the South (Table 7). It is worth noting that Flather and others (1999) found that the percentage of declining species was greater in the South than in any other RPA region. Abundance trends among species groups vary considerably. Species with declining trends include 70 percent of grassland-nesting birds, 57 percent of ground-nesting birds, 53 percent of shrubland-nesting birds, 49 percent of open-cup nesting birds, 46 percent of urban-nesting birds, and 41 percent of neotropical migrants. Numbers of the majority of cavity-nesting species and wetland species have been stable.

Figure 21 suggests that bird species richness is high along the Southern Appalachians and along the Atlantic Coast from northeastern North Carolina to the Chesapeake Bay. Because some species are missed during bird count surveys including nocturnal species, raptors, and absent migrants, it is important to note that the bird richness estimates are biased low (Sauer and others 1997).

Raptors include hawks, falcons, eagles, vultures, and owls. In contrast to other bird species, raptors naturally exist at relatively low population densities and are widely dispersed in their habitats. The natural scarcity of raptors, their ability to move quickly, and the difficulties of detection inhibit the determination of population status (Fuller and others 1995).

As a group, raptors are poorly surveyed, and quantitative data are lacking to determine their population trends. Table 8 presents a national summary of the status and population trends of 33 species and subspecies of southern raptors. Two species, the American kestrel and burrowing owl, are declining across the United States. Mississippi kites, osprey, bald eagles, and peregrine falcons are increasing. Populations of 22 species are considered stable nationwide.

The status of a raptor population often reflects changes in the availability of prey species. However, changes in raptor status also can indicate subtle environmental conditions, such as chemical contamination or disease.

Nesting ospreys are concentrated along the Atlantic Coast. Most regional populations declined through the early 1970s. Following the nationwide ban on DDT in 1972, osprey productivity improved and population numbers increased in many areas. Osprey numbers are stable, and in some areas they are increasing.

The endangered snail kite breeds in central and southern Florida wetlands, the northern extent of the range. The species declined from 1900-1960. Populations remain relatively stable today.

Bald eagle populations declined dramatically between 1950 and 1970. Illegal shooting, habitat alteration, and DDT adversely affected bird populations. The species was classified as endangered in 1978. Following the DDT ban, bald eagle reproduction improved and populations began increasing. The active protection of nesting habitat and release of hand-reared eagles aided this increase. Habitat loss remains a threat in many areas (Fuller and others 1995).

Ferruginous hawk populations are stable in some areas, but declining in others. Status determination is complicated by the low density of nesting birds and fluctuation in breeding associated with cycles of prey abundance.

The peregrine falcon also suffered from contamination by DDT and other organochlorine pesticides. Peregrine recovery has been hastened in the East by the release of hundreds of birds bred in captivity; these birds survived and produced young in the wild.