The Status of Bird Species

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Birds have always been among the best-studied biological groups, in part because of the efforts of countless amateur birdwatchers. In 2003 the World Conservation Union (IUCN) reported that 129 bird species have gone extinct, with another four species extinct in the wild. The rate of extinction among birds has increased every fifty years. Bird species have died out because of habitat destruction, hunting and collection, pollution, and predation by non-native species. The extinction rate of bird species is alarming not only because of the irrevocable loss of each species but also because of implications for the health of entire ecosystems.

The United States government has long recognized the importance of bird biodiversity and promoted habitat conservation under the Migratory Bird Conservation Act, passed by Congress in 1929. This law established the Migratory Bird Conservation Commission, which works with the Secretary of the Interior to designate and fund avian wildlife refuge areas. The U.S. Fish and Wildlife Service is responsible for acquiring necessary lands through direct purchase, lease, or easement (agreement with landowners). The Fish and Wildlife Service has procured over 4 million acres of land for bird refuges.

Birds received considerable attention in the 2003 IUCN Red List of Threatened Species. A total of 1,194 bird species were considered threatened—one of every eight described species. Another 727 bird species were considered "near threatened." There were 182 bird species categorized as "critically endangered," a significant increase from 168 listed species only seven years earlier. Of these critically endangered species, a large majority—89 percent—have been harmed by loss of habitat. The number of "endangered" birds listed by the IUCN also increased dramatically, from 235 to 331 species.

Certain groups of birds have declined particularly. All twenty-one albatross species are considered threatened under the 2003 Red List, due largely to deaths from long-line fishing. Prior to the rise of long-line fishing, most albatross populations were fairly stable. The number of threatened penguin species has also jumped, increasing to ten in 2003. Finally, rapid deforestation in Southeast Asian rainforests has increased the number of threatened doves, parrots, and perching birds.

Less than 5 percent of Earth's land area is home to 75 percent of the world's threatened bird species. The largest numbers of endangered birds are found in Indonesia, the Philippines, Brazil, Colombia, China, Peru, India, and Tanzania. New Zealand and the Philippines have the highest proportion of threatened species, with 42 percent and 35 percent respectively.


Habitat Loss and Environmental Decline

The driving force behind current declines in many bird species is the destruction, degradation, and fragmentation of habitat due to increasing human population size and the wasteful consumption of resources. The leading cause of habitat destruction in the United States is agricultural development. Large corporate farms cause environmental damage by clearing out native plant species, planting only one or a few crops, and draining wetlands. Natural habitats are also lost to urban sprawl, logging, mining, and road building.

Tropical bird species are threatened by large-scale deforestation worldwide. In Asia, for example, a 2001 study by BirdLife International suggested that one in four bird species is threatened, the majority due to loss of forest habitat. Populations have declined especially sharply in the last two decades, coincident with what BirdLife International calls "habitat loss or degradation resulting from unsustainable and often illegal logging, and land or wetland clearance for agriculture or exotic timber plantations." Large species, such as the Philippine eagle, are most quickly harmed by deforestation—these require large areas of undisturbed forest to hunt and breed.

Many Arctic bird species are threatened by habitat loss due to global warming. In April 2000 the World Wildlife Fund released a report indicating that a world climate change as small as 1.7 degrees centigrade (about 3.3 degrees Fahrenheit) would significantly reduce tundra habitat—the frozen arctic plain that serves as a breeding ground for many bird species. Among the tundra species already threatened are the red-breasted goose, the tundra bean goose, and the spoon-billed sandpiper.

Island species are also particularly vulnerable to habitat destruction because their ranges are usually very small to begin with. In addition, because many island birds evolved in the absence of predators, there are a large number of flightless species—these are highly vulnerable to hunting or predation by introduced species, including humans, cats, dogs, and rats. At one time some 75 percent of all bird extinctions occurred on islands. It is estimated that two-thirds of Hawaii's original bird fauna is already extinct. Of the remaining one-third, a large majority are imperiled. Habitat destruction in Hawaii has been so extensive that all the lowland species now present are non-native species introduced by humans.


During the latter half of the twentieth century, pesticides and other toxic chemicals were recognized as a major cause of avian mortality and a primary factor in the endangerment of several species, including the bald eagle and peregrine falcon. While the U.S. Environmental Protection Agency regulates the manufacture and use of toxic chemicals nationwide, the Fish and Wildlife Service (under the Federal Insecticide, Fungicide, and Rodenticide Act [Amended 1988]) is responsible for preventing and punishing the misuse of chemicals that affect wildlife.

Many chemicals harmful to birds, such as DDT and toxaphene, have been banned. Other chemicals, such as endrin, the most toxic of the chlorinated hydrocarbon pesticides, are still legal for some uses. Endrin was responsible for the disappearance of the brown pelican from Louisiana, a population that once numbered 50,000 individuals.

Oil Spills

Oil spills constitute a major threat to birds. (See Figure 8.1.) One of the worst and most infamous spills in history occurred on March 24, 1989, when the Exxon Valdez tanker released 11 million tons of crude oil into Alaska's Prince William Sound. To many Americans, it still exemplifies the disastrous effects oil spills have on wildlife. Thousands of birds died immediately after coming in contact with the oil, either from losing the insulation of their feathers or by ingesting lethal amounts of oil when they tried to clean themselves. Exxon personnel burned untold piles of birds; others were saved in cold storage under orders from the Fish and Wildlife Service. A complete count was never obtained, but Wildlife Service biologists estimated that between 250,000 and 400,000 sea birds died.

Approximately 40 percent of the region's entire population of common murres—estimated at 91,000—was eliminated. The yellow-billed loon population was also seriously depleted, as was the population of Kittlitz's murrelet, a species found almost exclusively in Prince William Sound. Other affected bird species included the bald eagle, black oystercatcher, common loon, harlequin duck, marbled murrelet, pigeon guillemot, and the pelagic, red-faced, and double-crested cormorants. Of these, the common loon, the harlequin duck, the pigeon guillemot, and the three species of cormorants have not increased in population size since the spill and were still considered "not recovered" in 2002. In addition, the Kittlitz's murrelet appears to be suffering from continued population decline, and its future prospects appear bleak.

The detergents used to clean up oil spills can also be deadly to waterfowl—detergents destroy feathers, which leads to fatal chills or trauma. Research has shown that even after careful rehabilitation, birds that have been returned to nature after a spill often die in a matter of months. In 1996 Dr. Daniel Anderson, a biologist at the University of California at Davis, found that only 12 to 15 percent of rehabilitated pelicans survived for two years, compared to the 80 to 90 percent of pelicans not exposed to oil. For many ornithologists, these dismal results raise the issue of whether avian rescue efforts are worthwhile. Could money spent on rehabilitation be better used for spill prevention and habitat restoration? Oregon ornithologist Dr. Brian Sharp argues that the cleanup effort might ease the conscience of the public and of politicians, but in reality, does very little to benefit birds. However, new methods of treating oiled birds and of controlling spills have increased the bird survival rate from 5 percent to between 60 and 80 percent for some species. Under the Clean Water Act, the oil industry pays a tax that helps fund cleanups after spills.

Domestic Cats

Studies in the United States and Britain have shown that house cats kill millions of small birds and mammals every year, a death toll that contributes to declines of rare species in some areas. The University of Wisconsin reported that in that state alone, cats killed 19 million songbirds and 140,000 game birds in a single year. The British study reported that Britain's 5 million house cats account for an annual prey toll of some 70 million animals, 20 million of which are birds. The study also found that cats were responsible for a third to half of all the sparrow deaths in England. Both studies determined that factors such as whether a cat was well-fed at home, wore a bell collar, or was declawed made no difference to its hunting habits. Many cat victims are plentiful urban species, but Fish and Wildlife studies show that cats also kill hundreds of millions of migratory songbirds annually. In addition, cats have devastated bird fauna on some islands and are believed to have contributed to the declines of several grassland species in the U.S.

Trade in Exotic Birds

Birds are among the most popular pets in American homes. An estimated 6–10 percent of American households own pet birds. Many of these are common finches, canaries, or parakeets, all of which are raised in captivity in the United States. However, wild birds are owned and traded as well, including numerous species of passerines (song birds) and psittacines (parrots and their relatives).

Passerines include any of the approximately 4,800 species of song birds. The most commonly traded passerines include warblers, buntings, weavers, finches, starlings, flycatchers, and sparrows. Passerines are regarded as low-value birds, and few passerines are endangered due to trade.

The 333 species of psittacines, however, are generally rarer, and thus much more valuable, than passerines. They comprise about 15 percent of the pet bird market in the United States. The most commonly traded psittacines are macaws, Amazons, cockatoos, lovebirds, lories, and parakeets. In addition to their vivid colors and pleasant songs, many of these birds possess the ability to "talk," which makes them particularly appealing to some owners. Bird dealers have created demand for an ever-increasing variety of birds, including parrots, macaws, cockatoos, parakeets, mynahs, toucans, tanagers, and other tropical species.

Laws in Mexico, Guatemala, and Honduras ban trade in parrots, and U.S. law bars importation of birds taken illegally from other countries. Some countries still allow exports, however, and there is also a great deal of smuggling. Legislation passed in 1992 to halt the legal importation of parrots is, ironically, believed to have increased smuggling. In 1998 customs officials announced the arrest of more than forty people for smuggling hundreds of rare parrots and other wildlife across the Mexican border. The animals seized were believed to be worth hundreds of thousands of dollars in the pet trade, although some were considered nearly priceless because of their rarity in the wild.

The illegal bird trade has severely harmed many threatened species. New York Zoological Society bird curator Don Bruning believes that species such as the scarlet macaw are now practically extinct throughout Central America due to illegal trade. Over the past twenty years, smuggling has reduced red crown parrot populations by 80 percent and yellow-headed parrots by 90 percent in Mexico. In 2000 the World Wildlife Fund (WWF) identified the horned parakeet as one of the ten species most threatened by illegal trade.

Invasive Species—The Case of Guam

Invasive species have damaged bird populations in some parts of the world, particularly those that occupy islands. Guam's unique bird fauna has been all but wiped out by the brown tree snake, an invasive species. The brown tree snake was probably introduced from New Guinea via ship cargo in the 1950s, and had spread throughout the island by 1968. The snakes have no natural enemies on the island and plentiful prey in the form of forest birds. There are now believed to be as many as 13,000 snakes in a single square mile in some forest habitats. Twelve bird species have already gone extinct on Guam, including the Guam flycatcher, the Rufus fantail, the white-throated ground dove, and the cardinal honey-eater. Several other Guam bird species are close to extinction. Many of these birds are or were unique to Guam. Measures have been implemented to try to keep this destructive snake from invading other islands, including careful inspection of all cargo arriving from Guam. The removal of the brown tree snake in select habitat areas on Guam (which is a high effort project, requiring the constant trapping of snakes) allowed the reintroduction of one bird, the flightless Guam rail, in 1998. The Guam rail had gone extinct in the wild, but a population is maintained in captivity.

Other particularly destructive invasive species include several associated with humans, including cats, dogs, and rats, which often prey on birds and their eggs. In fact, the World Conservation Union (IUCN) reports that invasive species represent the single most frequent cause of bird extinctions since 1800. Invasive species are currently estimated to affect 350, or 30 percent, of all IUCN-listed threatened birds.

Salton Sea Deaths

The Salton Sea, located 150 miles southeast of Los Angeles in the Sonora Desert, is a 35-mile-long expanse of salt marsh and open water encompassing 35,484 acres and situated 227 feet below sea level. The sea formed from a salt-covered depression known as the Salton Sink in 1905, when a levee on the Colorado River broke, filling the depression with water. Subsequently, the area has received additional water, primarily from agricultural runoff. Because the Salton Sea has no outlet, water is lost only through evaporation, leaving dissolved salts behind. The salinity (the amount of salt in the water) in the Salton Sea has increased gradually over time, and is estimated at 25 percent greater than the ocean in 2004. The Salton Sea serves as habitat for migrating birds and provides winter habitat for waterfowl. The area is second only to the Texas coastline in the number of bird species sighted, and nearly 400 species had been reported by 2004. The Salton Sea National Wildlife Refuge was established in 1930 by presidential proclamation.

In the last decades of the twentieth century the Salton Sea entered a rapid and initially inexplicable decline that resulted in the deaths of countless birds and fish. The first unusual avian deaths were reported in 1987, and a task force was created by the California Department of Fish and Game in 1988 to study the problem. In 1992 a massive die-off occurred in which over 150,000 birds died. Some of the fatalities were attributed to avian cholera, but experts remained baffled by the majority of casualties. At that point, the Department of the Interior initiated a $10 million Salton Sea project aimed at combating rising salinity and other environmental problems. The Salton Sea Authority was established in 1993 to coordinate activity. In 1996 there was another mass epidemic in which over 20,000 birds from 64 species died, including 1,200 brown pelicans, an endangered species. This time, the cause was identified as avian botulism. The same year, thousands of tilapia fish were also killed by botulism. Authorities tentatively attributed the avian deaths to botulism from consuming tainted fish. Throughout 1997 a variety of initiatives were proposed in an effort to combat high salinity and other problems at the Salton Sea. Nonetheless, in May of that year another 10,000 birds from 51 species died, along with thousands of tilapia. Causes of death included avian botulism, Newcastle disease, avian cholera, and poisoning by toxic algae.

Scientists have so far failed to establish a precise link between water quality and bird die-offs, but suspect a combination of natural and man-made contaminants. Evaporation and agricultural runoff have increased the salinity of the Salton Sea to levels 25 percent higher than in the Pacific Ocean. Experts fear that high salt levels increase the susceptibility of fish to disease, and that birds are impacted when they consume affected fish. Another suspected cause of environmental deterioration is the defunct Salton Sea Test Base (SSTB), which served as a center for arms testing and weapons research during World War II. The U.S. Army Corps of Engineers initiated a clean-up project to decontaminate the SSTB, which occupied over 20,000 acres of land and water in the southwest corner of the Salton Sea. Environmentalists also believe that agricultural runoff from California's Imperial Valley, one of the most productive farming areas in the United States, encourages algae blooms that are deadly to fish. The Salton Sea is also polluted by additional agricultural runoff from Mexico and by untreated sewage from rivers that flow across the Mexican-U.S. border. Contamination from DDT, DDE (a byproduct of DDT), and selenium also were documented as contributing to the decline.

The Salton Sea Task Force, the U.S. Bureau of Reclamation, and the California State Legislature have combined forces to restore the Salton Sea to health. However, another outbreak of botulism was reported in 2000. The endangered brown pelican suffered greatly in this outbreak, with 717 individuals dying. Another six hundred brown pelicans were rehabilitated and released in December 2000. Avian botulism is not fatal if treatment is begun early, but birds do not show symptoms until the disease has progressed. In addition to the brown pelican, thirty-five other species were affected in the 2000 outbreak. All affected species eat tilapia. Fish and Wildlife Service employees, along with California Department of Fish and Game, helped to round up sick birds and transport them to an open-air bird hospital built in 1997 from funds raised by volunteers. Recovered birds were released near the Tijuana Slough and Seal Beach national wildlife refuges, both located in Southern California.


In 2004 there were 273 birds on the Endangered Species List. Of these, 253 are endangered, including 78 U.S. species and 175 foreign species. In addition, twenty birds are threatened, including fourteen U.S. species and six foreign species. Threatened and endangered U.S. bird species are shown in Table 8.1. This list includes many types of birds, including sparrows, albatrosses, terns, plovers, hawks, and woodpeckers. There are also a disproportionate number of Hawaiian bird species listed. Several threatened and endangered species will be discussed below.

Migratory Songbirds

Every year, more than 120 songbird species migrate between North America and tropical areas in Central and South America. Although many are appreciated by humans for their beautiful songs and colorful plumage, migratory songbirds also play a vital role in many ecosystems. During spring migration in the Ozarks, for example, some forty to fifty migratory bird species arrive and feed on the insects that inhabit oak trees, thereby helping to control insect populations. Migratory species are particularly vulnerable because they are dependent on suitable habitat in both their winter and spring ranges. In North

StatusSpecies nameStatusSpecies name
EAkepa, Hawaii (honeycreeper) (Loxops coccineus coccineus)TMurrelet, marbled (Brachyramphus marmoratus marmoratus)
EAkepa, Maui (honeycreeper) (Loxops coccineus ochraceus)ENightjar, Puerto Rican (Caprimulgus noctitherus)
EAkialoa, Kauai (honeycreeper) (Hemignathus procerus)ENukupu'u (honeycreeper) (Hemignathus lucidus)
EAkiapola'au (honeycreeper) (Hemignathus munroi)E'O'o, Kauai (honeyeater) (Moho braccatus)
EAlbatross, short-tailed (Phoebatria [=Diomedea] albatrus)E'O'u (honeycreeper) (Psittirostra psittacea)
EBlackbird, yellow-shouldered (Agelaius xanthomus)TOwl, Mexican spotted (Strix occidentalis lucida)
EBobwhite, masked (quail) (Colinus virginianus ridgwayi)TOwl, northern spotted (Strix occidentalis caurina)
EBroadbill, Guam (Myiagra freycineti)EPalila (honeycreeper) (Loxioides bailleui)
ECahow (Pterodroma cahow)EParrot, Puerto Rican (Amazona vittata)
TCaracara, Audubon's crested (Polyborus plancus audubonii)EParrotbill, Maui (honeycreeper) (Pseudonestor xanthophrys)
E, XNCondor, California (Gymnogyps californianus)EPelican, brown (Pelecanus occidentalis)
ECoot, Hawaiian (Fulica americana alai)EPetrel, Hawaiian dark-rumped (Pterodroma phaeopygia sandwichensis)
ECrane, Mississippi sandhill (Grus canadensis pulla)EPigeon, Puerto Rican plain (Columba inornata wetmorei)
E, XNCrane, whooping (Grus americana)E, TPlover, piping (Charadrius melodus)
ECreeper, Hawaii (Oreomystis mana)TPlover, western snowy (Charadrius alexandrinus nivosus)
ECreeper, Molokai (Paroreomyza flammea)EPo'ouli (honeycreeper) (Melamprosops phaeosoma)
ECreeper, Oahu (Paroreomyza maculata)EPrairie chicken, Attwater's greater (Tympanuchus cupido attwateri)
ECrow, Hawaiian (='alala) (Corvus hawaiiensis)EPygmy owl, cactus ferruginous (Glaucidium brasilianum cactorum)
ECrow, Mariana (=aga) (Corvus kubaryi)ERail, California clapper (Rallus longirostris obsoletus)
ECrow, white-necked (Corvus leucognaphalus)E, XNRail, Guam (Rallus owstoni)
ECurlew, Eskimo (Numenius borealis)ERail, light-footed clapper (Rallus longirostris levipes)
EDuck, Hawaiian (=koloa) (Anas wyvilliana)ERail, Yuma clapper (Rallus longirostris yumanensis)
EDuck, Laysan (Anas laysanensis)TShearwater, Newell's Townsend's (Puffinus auricularis newelli)
TEagle, bald (Haliaeetus leucocephalus)EShrike, San Clemente loggerhead (Lanius ludovicianus mearnsi)
TEider, spectacled (Somateria fischeri)ESparrow, Cape Sable seaside (Ammodramus maritimus mirabilis)
TEider, Steller's (Polysticta stelleri)ESparrow, Florida grasshopper (Ammodramus savannarum floridanus)
EElepaio, Oahu (Chasiempis sandwichensis ibidis)TSparrow, San Clemente sage (Amphispiza belli clementeae)
EFalcon, northern aplomado (Falco femoralis septentrionalis)EStilt, Hawaiian (Himantopus mexicanus knudseni)
EFinch, Laysan (honeycreeper) (Telespyza cantans)EStork, wood (Mycteria americana)
EFinch, Nihoa (honeycreeper) (Telespyza ultima)ESwiftlet, Mariana gray (Aerodramus vanikorensis bartschi)
EFlycatcher, southwestern willow (Empidonax traillii extimus)ETern, California least (Sterna antillarum browni)
TGnatcatcher, coastal California (Polioptila californica californica)ETern, least (Sterna antillarum)
EGoose, Hawaiian (Branta [=Nesochen] sandvicensis)E, TTern, roseate (Sterna dougallii dougallii)
EHawk, Hawaiian (='lo) (Buteo solitarius)EThrush, large Kauai (=kamao) (Myadestes myadestinus)
EHawk, Puerto Rican broad-winged (Buteo platypterus brunnescens)EThrush, Molokai (Myadestes lanaiensis rutha)
EHawk, Puerto Rican sharp-shinned (Accipiter striatus venator)EThrush, small Kauai (=puaiohi) (Myadestes palmeri)
EHoneycreeper, crested (Palmeria dolei)TTowhee, Inyo California (Pipilo crissalis eremophilus)
TJay, Florida scrub (Aphelocoma coerulescens)EVireo, black-capped (Vireo atricapilla)
EKingfisher, Guam Micronesian (Halcyon cinnamomina cinnamomina)EVireo, least Bell's (Vireo bellii pusillus)
EKite, Everglade snail (Rostrhamus sociabilis plumbeus)EWarbler (=wood), Bachman's (Vermivora bachmanii)
EMallard, Mariana (Anas oustaleti)EWarbler (=wood), golden-cheeked (Dendroica chrysoparia)
EMegapode, Micronesian (Megapodius laperouse)EWarbler (=wood), Kirtland's (Dendroica kirtlandii)
EMillerbird, Nihoa (old world warbler) (Acrocephalus familiaris kingi)EWarbler, nightingale reed (old world warbler) (Acrocephalus luscinia)
TMonarch, Tinian (old world flycatcher) (Monarcha takatsukasae)EWhite-eye, bridled (Zosterops conspicillatus conspicillatus)
EMoorhen, Hawaiian common (Gallinula chloropus sandvicensis)EWoodpecker, ivory-billed (Campephilus principalis)
EMoorhen, Mariana common (Gallinula chloropus guami)EWoodpecker, red-cockaded (Picoides borealis)
E = Endangered
T = Threatened
XN = Experimental population, non-essential
source: Adapted from "U.S. Listed Vertebrate Animal Species Report by Taxonomic Group as of 02/17/2004," Threatened and Endangered Species System (TESS), U.S. Fish and Wildlife Service, Washington, DC, 2004 [Online] [accessed February 17, 2004]

America, real estate development has eliminated many forest habitats. Migratory songbird habitats are also jeopardized in Central and South America, where farmers and ranchers have been burning and clearing tropical forests to plant crops and graze livestock. Some countries, including Belize, Costa Rica, Guatemala, and Mexico, have set up preserves for songbirds, but improved forest management is needed to save them.

The North American Breeding Bird Survey

The North American Breeding Bird Survey is a continent-wide study begun in 1966 and carried on annually ever since. Each year, more than 3,500 routes are surveyed by experienced birders. Surveys occur primarily during the month of June, which represents the peak in the songbird nesting season. The results of this survey allow scientists to document changes in the distributions and populations of bird species throughout North America. The survey is conducted by the Biological Resource Division of the United States Geological Survey. Results compiled from 1966 to 2002 indicate that:

  • 61 percent of 28 grassland-breeding species surveyed are declining, whereas 11 percent are increasing
  • 14 percent of 87 wetland-breeding species surveyed are declining, whereas 39 percent are increasing
  • 36 percent of 87 successional-or scrub-breeding species are declining, whereas 15 percent are increasing
  • 23 percent of 131 woodland-breeding species are declining, whereas 30 percent are increasing
  • 47 percent of 15 urban-breeding species are declining, whereas 27 percent are increasing

Results among birds with different migratory strategies include:

  • among 107 short distance migrants, 37 percent are declining whereas 26 percent are increasing
  • among 137 neotropical migrants, 31 percent are declining whereas 24 percent are increasing
  • among 93 permanent residents, 22 percent are declining whereas 25 percent are increasing

The Black-Capped Vireo and Golden-Cheeked Warbler

The black-capped vireo and golden-cheeked warbler are among the threatened songbirds listed with the Fish and Wildlife Service. Both species nest in central Texas and other locations in the U.S. and winter in Mexico and Central America. Both species have declined largely due to loss of habitat caused by land clearing for development. Another factor in the decline of the black-capped vireo is harm from "brood parasites"—bird species that lay their eggs in the nests of other species. In certain areas, more than half the black-capped vireo nests contain eggs of brood parasites called brown-headed cowbirds. The black-capped vireo was placed on the Endangered Species List in 1987, the golden-cheeked warbler in 1990.

Much of the critical nesting habitat for black-capped vireos and golden-cheeked warblers lies in the Hill Country of central Texas. The Texas Hill Country is characterized by diverse habitats and a high concentration of rare bird species. In the last decade, however, increased water demand by metropolitan areas has caused the local Edwards Aquifer to drop by thirty feet, resulting in a 15 to 45 percent decrease in available bird habitat. In an effort to balance development with wildlife preservation, the city of Austin, Texas invited The Nature Conservancy to formulate a plan to protect Hill Country habitats while enabling some development. The result was the Balcones Canyonlands Conservation Plan, which includes a 75,000-acre preserve in the Texas Hill Country.

Fort Hood, Texas, a heavy artillery training site for the U.S. Army, was designated essential nesting habitat for the golden-cheeked warbler and black-capped vireo in 1993. With the help of The Nature Conservancy, the Army currently manages some 66,000 acres of habitat for these species. Control of brown-headed cowbird populations has been a major part of the conservation efforts. Brown-headed cowbirds parasitize the nests of over two hundred species of songbirds, and have caused declines in many of these species. Nest parasitism rates for the black-capped vireo were as high as 90 percent before control measures were begun. They are now at less than 10 percent. In 2000, surveys at Fort Hood documented 236 male black-capped vireos and 229 vireo territories, which produced an average of 1.75 fledglings each. Many other bird species also use habitat at Fort Hood, including threatened and endangered species such as the bald eagle, peregrine falcon, and whooping crane.

The California Gnatcatcher

The California gnatcatcher is a small, gray and black songbird known for its "kitten-like" mewing call. Gnatcatchers are non-migratory, permanent residents of California coastal sage scrub communities, one of the most threatened vegetation types in the nation. Estimates of coastal scrub loss in the United States range from 70 to 90 percent of historic levels.

Fewer than 2,000 pairs of California gnatcatchers are estimated to remain in the United States. The plight of the species has emphasized the importance of preserving coastal sage scrub habitat, which supports many other distinctive species as well. The California gnatcatcher was listed as threatened across its entire range in California and Mexico in 1993.


Red-cockaded woodpeckers are named for the red patches, or cockades, of feathers found on the heads of males. This species is found in old pine forests in the southeastern United States, where family groups—consisting of a breeding male and female as well as several helpers—nest within self-dug cavities in pine trees. Tree cavities serve as nesting sites in addition to providing protection from predators. Because red-cockaded woodpeckers rarely nest in trees less than 80 years old, heavy logging has destroyed much of their former habitat. The red-cockaded woodpecker was first placed on the Endangered Species List in 1970. It is currently found in fragmented populations in the southeastern seaboard westward into Texas. The total population size is estimated at 10,000–14,000 individuals.

In March 2001 the U.S. Fish and Wildlife Service was forced to rescue several red-cockaded woodpeckers from habitat areas in Daniel Boone National Forest in Kentucky. Fifteen woodpeckers in six family groups were relocated to the Carolina Sandhills National Wildlife Refuge in South Carolina and the Ouachita National Forest in Arkansas. Daniel Boone National Forest had become uninhabitable for the woodpeckers after a 1999 infestation of southern pine beetles. The beetles quickly destroyed 90 percent of local woodpecker habitat despite valiant efforts by Forest Service officials and volunteers to control the insect's spread. The removal of this red-cockaded woodpecker population from Kentucky means that the species is now absent from the state.

The ivory-billed woodpecker, the largest woodpecker species, has long been thought extinct. A century ago, the species was found throughout the southeastern United States as well as in Cuba. The last confirmed sightings in the U.S. were reported in the 1970s. However, tantalizing hints that the ivory-billed woodpecker may yet survive in North America persist. Hunters occasionally report seeing it or, more often, hearing its characteristic double-rap sound deep in the Louisiana bayou. Several groups of ornithologists have devoted significant effort to relocating this species, particularly since a hunter reported seeing one on April Fool's Day in 1999. As of 2004 there have been no definitive sightings. The Cuban subspecies of the ivory-billed woodpecker was also rediscovered in 1986 after being presumed extinct. However, populations had reached such a low point by then that measures to help save the group were ineffectual.

Spotted Owls

The northern spotted owl occupies old-growth forests in the Pacific Northwest, where it nests in the cavities of trees two hundred years old or older. It does not seem afraid of humans and in fact appears to be curious about humans and human activity. Its primary prey includes the nocturnal northern flying squirrel, mice, and other rodents and reptiles. Owl pairs may forage across areas as large as 2,200 acres. There are about 2,000 breeding pairs in California, Oregon, and Washington, and another hundred pairs in British Columbia, Canada.

Northern spotted owl populations have declined primarily due to habitat loss. Most of the private lands in its range have been heavily logged, leaving only public lands, such as National Forests and National Parks, for habitat. Because logging has also been permitted in many old-growth National Forest areas, the species has lost approximately 90 percent of its original habitat. In 1990 the Fish and Wildlife Service placed the northern spotted owl on its list of threatened species. Court battles began over continued logging in National Forest habitats. In March 1991 U.S. Federal District Court Judge William Dwyer ruled in favor of the Seattle Audubon Society and against the U.S. Forest Service, declaring that the Forest Service was not meeting its obligation to "maintain viable populations." The Forest Service had argued that the Fish and Wildlife Service was responsible for the management and recovery of this species. However, Dwyer pointed out that the Forest Service had its own distinct obligations to protect species under the Endangered Species Act, and that courts had already reprimanded the Fish and Wildlife Service for failing to designate critical habitat for the northern spotted owl. In 1992 the Fish and Wildlife Service set aside 7 million acres as "critical habitat" for the species. The Northwest Forest Plan was established in 1993. This plan reduced logging in thirteen National Forests by about 85 percent in order to protect northern spotted owl habitats. However, the northern spotted owl has continued to decline by 7 to 10 percent per year—this despite the unanticipated discovery of fifty pairs of nesting adults in California's Marin County, just north of the Golden Gate Bridge.

In 1993 the Mexican spotted owl, a species native to the Southwest, was also placed on the list of threatened species. As with the northern spotted owl, the prime threat to this group is poorly managed timber harvesting. The Mexican spotted owl has a wide range, and is found in Utah, Colorado, Arizona, New Mexico, and Texas, as well as in central Mexico. Both northern and Mexican spotted owls remained threatened in 2004.

The California Condor

California condors, whose wingspans exceed nine feet, are among the continent's most impressive birds. Ten thousand years ago, this species soared over most of North America. However, its range contracted at the end of the ice age, and eventually individuals were found only along the Pacific Coast. Like other vulture species, the California condor is a carrion eater, and feeds on the carcasses of deer, sheep, and smaller species such as rodents. Random shooting, egg collection, poisoning, and loss of habitat devastated the condor population. The species was listed as endangered in 1967.

An intense captive breeding program for the California condor was initiated in 1987. (See Figure 8.2.) The first chick hatched in 1988. In 1994, after a series of deaths in the wild in which seven condors perished in rapid succession, the eight remaining wild condors were also captured and entered into the captive breeding program. The breeding program was successful enough that California condors were released into the wild beginning in 1992. In April 2002, for the first time in eighteen years, a condor egg laid in the wild hatched in the wild. The parents of this chick had been captive-bred at the Los Angeles Zoo and the San Diego Wild Animal Park respectively and released into the wild in 1995 at the age of one. Wild condors now inhabit parts of California as well as Nevada, Utah, and Arizona, where a population was introduced in the vicinity of the Grand Canyon in 1996, providing spectacular opportunities to view the largest bird in North America.

In March 2004 the California Department of Fish and Game reported that there were a total of 215 California condors in existence, including 125 captive individuals and 90 in the wild population—20 in southern California, 24 in central California, 5 in Baja California, and 41 in Arizona. Total production in 2003 included 28 offspring in captivity and one wild fledgling.

The Great White Whooping Crane

Standing five feet, the whooping crane (see Figure 8.3) is North America's tallest bird and among the best known endangered species in the United States. Its name comes from its loud and distinctive call, which can be heard for miles. Each year, whooping cranes fly 2,500 miles from nesting grounds in Wood Buffalo, Canada to Aransas, south Texas for the winter before returning north in March to breed. Whooping cranes return to the same nesting site each year with the same mate. The birds were once heavily hunted, for meat as well as for their beautiful, long white feathers. In addition, the heavy loss of wetland areas in the U.S. deprived whooping cranes of much of their original habitat. In 1937 it was discovered that fewer than twenty whooping cranes were left in the wild. That same year, the Aransas Wildlife Refuge was established in south Texas to protect the species' wintering habitat. Conservation efforts for the whooping crane are coordinated with the Canadian government, which manages its breeding areas.

Captive breeding programs have helped to increase the worldwide whooping crane population. As of 2004, the International Whooping Crane Recovery Team reported that 194 whooping cranes inhabit the traditional territory, migrating from Wood Buffalo, Canada to Aransas yearly. In addition, an introduced population of captive-bred individuals has been established in the Kissimmee Prairie in Florida. This population contains 90 individuals, and has bred with success in its new habitat. A second introduced population breeds in Wisconsin on the Necedah National Wildlife Refuge and winters in Florida on the Chassahowitzka National Wildlife Refuge. This population numbered thirty-six in 2004. Introduced cranes were led to their Florida wintering grounds along the migration route by ultra-light aircraft in 2001, and successfully made the return trip on their own in following years. Figure 8.4 illustrates the migration routes and locales of all three whooping crane populations. In addition to these wild populations, another 128 whooping cranes are found in captivity.

Hawaiian Honeycreepers

The Hawaiian honeycreepers are a group of songbirds endemic to Hawaii—that is, species in this group are found there and nowhere else on Earth. Hawaiian honeycreepers are believed to have radiated—formed many separate species, each adapted to a particular lifestyle—from a single species that colonized the Hawaiian Islands thousands of years ago. The honeycreepers are named for the characteristic "creeping" behavior some species exhibit as they search for nectar. The Hawaiian honeycreepers are extremely diverse in their diet—different species are seed-eaters, insect-eaters, or nectar-eaters. Species also differ in the shapes of the beaks and in plumage coloration. Hawaiian honeycreepers are found in forest habitats at high elevations. There were some fifty or sixty Hawaiian honeycreeper species originally, but a third of them are already extinct.

Twelve species of Hawaiian honeycreepers are currently listed with the Fish and Wildlife Service as endangered. Some honeycreeper species are among the most endangered animals on earth, with only a few individuals left. One of the primary factors involved in honeycreeper endangerment is loss of habitat. The Hawaiian Islands are estimated to retain a mere 20 to 30 percent of their original forest cover. In addition, the introduction of predators that hunt birds or eat their eggs, such as rats, cats, and mongooses, has contributed to the decline of numerous species. The introduction of bird diseases, particularly those spread by introduced mosquitoes, has also decimated honeycreeper populations. The success of mosquitoes in Hawaii has been dependent on another introduced species, pigs. The rooting activity of pigs creates pools of water where mosquitoes lay their eggs. In fact, the greater the number of pigs in a habitat, the more bird disease will be prevalent. Finally, competition with introduced bird species for food and habitat has also been a significant cause of decline.

The Po'ouli is the most endangered Hawaiian honey-creeper and probably the most endangered bird species in the world. Along with many other endangered native species, it occupies the Hanawi Natural Reserve Area in Maui, which has been aggressively rehabilitated and cleared of invasive species. There are three Po'ouli individuals left, two females and one male. The Maui Forest Bird Recovery Project and the Fish and Wildlife Service worked together in May 2002 to mate one of the Po'ouli females with the single remaining male. Unfortunately, the attempts were unsuccessful, and in October 2003 scientists began efforts to capture the last remaining individuals in the hope that captive breeding may hold off extinction.

In August 2003, the Fish and Wildlife Service published a recovery plan for nineteen endangered Hawaiian forest birds. (See Table 8.2.) The Fish and Wildlife Service reports that ten of these species have not been definitely observed in at least a decade and may well be extinct already. Two additional species are listed as either a candidate species or a species of concern. Most of these species are native to rain forests at elevations above 4,000 feet on the islands of Hawaii (Big Island), Maui, and Kauai. Major threats to endangered forest species listed by the Fish and Wildlife Service include habitat loss and modification, other human activity, disease, and predation. Of particular importance are non-native plants which have converted native plant communities to alien ecosystems unsuitable as habitat. Alien plant species known to threaten Hawaiian forest birds as well as the urgency of the need for control are shown in Table 8.3.

South Asian Vultures

In March 2004 BirdLife International warned that South Asian vulture populations were plummeting due to the drug diclofenac, which is used to treat cattle and other livestock. The three South Asian vulture species are the

Species (common name, scientific name, 4-letter acronym)Total population estimateFederal listing date and reference; state listing dateFederal status; recovery priority numberIUCN status listing
O'ahu 'elepaio, Chasiempis sandwichensis ibidis, OAEL1,97018 April 2000 (USFWS 2000); 18 April 2000Endangered; 3Vulnerable
Kama'o (large Kaua'i thrush), Myadestes myadestinus, KAMOLast detected in 198913 October 1970 (USFWS 1970, 1980, 1992); 22 March 1982Endangered; 5Critically endangered
Oloma'o (Moloka'i thrush), Myadestes lanaiensis rutha, OLOMLast detected in 198813 October 1970 (USFWS 1970, 1980, 1992); 22 March 1982Endangered; 5Critically endangered
Puaiohi (small Kaua'i thrush), Myadestes palmeri, PUAI30011 March 1967 (USFWS 1967, 1980, 1992); 22 March 1982Endangered; 2Critically endangered
'Ô 'o 'a 'a (Kaua'i 'o 'o), Moho braccatus, OOLast detected 28 Apr 198711 March 1967 (USFWS 1967, 1980); 22 March 1982Endangered; 4Extinct
'Ô 'û, Psittirostra psittacea, OULast detected in 197911 March 1967 (USFWS 1967, 1980); 22 March 1982Endangered;4Criticall
Palila, Loxioides bailleui, PALI3,390 (16-year average)11 March 1967 (USFWS 1967, 1980); 22 March 1982Endangered; 1Endangered
Maui parrotbill, Pseudonestor xanthophrys MAPA50011 March 1967 (USFWS 1967, 1980); 22 March 1982Endangered; 1Vulnerable
Kaua'i 'akialoa, Hemignathus procerus, KAAKLast detected in late 1960s 198211 March 1967 (USFWS 1967, 1980); 22 MarchEndangered; 5Extinct
Kaua'i nuku pu'u, Hemignathus lucidus Hanapepe, KANULast confirmed detection in 1960s11 March 1967 (USFWS 1967, 1970, 1980); 22 March 1982Endangered; 5Critically endangered
Maui nuku pu'u, Hemignathus lucidus affinis, MANULast detected in 197911 March 1967 (USFWS 1967, 1970, 1980); 22 March 1982Endangered; 5Critically endangered
'Akiapola'au, Hemignathus munroi, AKIP1,16311 March 1967 (USFWS 1967, 1980, 1992); 22 March 1982Endangered; 2Endangered
Hawai'i creeper, Oreomystis mana, HCRE12,50025 September 1975 (USFWS 1975, 1980, 1992); 22 March 1982Endangered; 8Endangered
O'ahu 'alauahio (O'ahu creeper), Paroreomyza maculata, OAALLast confirmed detection in 198513 October 1970 (USFWS 1970, 1980, 1992); 22 March 1982Endangered; 5Critically endangered
Kakawahie (Moloka'i creeper), Paroreomyza flammea, MOCRLast detected in 196313 October 1970 (USFWS 1970, 1992); 22 March 1982Endangered; 5Extinct
Hawai'i 'akepa, Loxops coccineus coccineus, AKEP14,00013 October 1970 (USFWS 1970, 1992); 22 March 1982Endangered; 8Endangered
Maui'akepa, Loxops coccineus ochraceus, MAAKLast confirmed detection in 197013 October 1970 (USFWS 1970, 1992); 22 March 1982Endangered; 6Endangered
'Akohekohe (crested honeycreeper), Palmeria dolei, AKOH3,80011 March 1967 (USFWS 1967); 22 March 1982Endangered; 7Vulnerable
Po'ouli, Melamprosops phaeosoma, POOU325 September 1975 (USFWS 1975, 1992); 22 March 1982Endangered; 4Critically endangered
source: "Table 1. Federally Listed Endangered Species of Hawaiian Forest Birds Included in This Recovery Plan and the International Union for the Conservation of Nature Species Status Listing (IUCN 1994)," in Draft Revised Recovery Plan for Hawaiian Forest Birds, U.S. Fish and Wildlife Service, Region 1, Portland, OR, August 2003

white-rumped vulture, the slender-billed vulture, and the Indian vulture. Populations have declined 95 percent over the course of eight years. Diclofenac causes kidney failure and other problems in vultures that feed on the carcasses of deceased livestock. The problem is particularly severe in India, where dead cattle are often left to rot because

Scientific nameCommon nameHawai'iMaui NuiO'ahuKaua'i
Acacia mearnsiiblack wattle313
Acacia melanoxylonAustralian blackwood13
Cinchona pubescensQuinine13
Cinnamomum burmanniipadang cassia2
Cinnamomum camphoracamphor tree1
Cortaderia jubataAndean pampas grass22
Cortaderia selloana22
Delairea odorataGerman ivy2
Ehrharta stipoidesmeadow ricegrass2
Erigeron karvinskianusdaisy fleabane31
Heliocarpus popayanensiswhite moho331
Holcus lanatusvelvetgrass, yorkshire fog33
Ilex aquifoliumEnglish or European holly12
Juncus effusesJapanese mat rush132
Juncus planifoliusRush33
Lantana camaralantana, lakana331
Leptospermum scopariumNew Zealand tea tree2
Lonicera japonicaJapanese honeysuckle332
Melinis minutifloraMolasses grass333
Myrica fayaFiretree121
Oplismenus hirtellusbasketgrass, honohono3
Panicum maximumGuinea grass32
Paspalum conjugatumHilo grass, mau'u-hilo333
Paspalum urvilleiVasey grass332
Pennisetum clandestinumkikuyu grass1
Pennisetum setaceumfountain grass1
Pyracantha angustifoliafirethorn, pyracantha333
Rubus argutusblackberry1111
Rubus discolor32
Rubus ellipticus var. obcordatusyellow Himalayan raspberry12
Rubus niveushill or mysore raspberry32
Rubus rosifoliusThimbleberry3322
Schinus terebinthifoliusChristmas berry221
Schizachyrium condensatumbeardgrass332
Setaria palmifoliapalmgrass222
Sphaeropteris cooperiAustralian tree fern2222
Toona ciliataAustralian red cedar31
Ulex europaeusGorse22
Eucalyptus spp. (90+ spp)gum trees2113
Ficus (microcarpa, nota, platyphyllum, rubigenosa)Figs221
Fraxinus (uhdei, griffithi)Ashes113
Hedychium (coronarium, flavescens, gardnerianum)Gingers1131
Psidium (cattleianum, guajava)Guavas1111
MelastomataceaeMelastome family1113
Passifloraceaepassion fruit family1222
Pinaceaepine family22
ProteaceaeProtea family232
At the species level, 39 taxa of alien grasses, shrubs, vines or trees pose a significant threat to forest bird recovery habit at. At higher taxonimic levels, all known naturalized taxa from five genera and four families pose significant threats to forest bird recovery habitat. Urgency of the need for management of each taxon is represented by a code:
1 = high
2 = moderate
3 = low
source: "Table 10. List of Alien Plant Taxa Known or Suspected to Pose a Significant Threat to Forest Bird Recovery Habitat on the Main Hawaiian Islands," in Draft Revised Recovery Plan for Hawaiian Forest Birds, U.S. Fish and Wildlife Service, Region 1, Portland, OR, August 2003

beef is taboo to the largely Hindu population. As many as two hundred vultures may feed on a single carcass.


The Peregrine Falcon

Many falcon species have declined with the spread of humans. Like other predatory species, falcons were often hunted, either for sport or because they were considered a threat to chickens or livestock.

The peregrine falcon is the fastest bird on Earth. It can achieve diving speeds of over 200 miles per hour. Like the bald eagle, much of the species' decline was due to the pesticide DDT. Populations sank to approximately 325 nesting pairs during the 1930s and 1940s. The recovery of this species was made possible by the banning of DDT as well as the establishment of special captive breeding centers on several continents. Between 1974 and 1999 more than 6,000 peregrine falcons were released into the wild. Federal and state agencies contributed to the conservation effort, as did private organizations such as the Peregrine Fund, Santa Cruz Predatory Bird Research Group, and Midwestern Peregrine Falcon Restoration Project.

In 1996 the Fish and Wildlife Service declared the peregrine falcon "officially recovered" and began the process to remove the species from the Endangered Species List. The American peregrine falcon was delisted in 1999 across its entire range, although it will be monitored for the next five years to assure that its recovery continues. By August 1999 about 1,650 breeding pairs of peregrine falcons inhabited the lower forty-eight states and Canada, with additional populations surviving in Mexico. The Arctic peregrine falcon, which recovered on its own after DDT was made illegal, was delisted in 1994. However, as of 2002 the Eurasian peregrine falcon, which occurs in Eurasia south to Africa and the Middle East, is still listed as endangered across its entire range.

The Bald Eagle

Almost everyone recognizes the bald eagle (see Figure 8.5). Symbol of honor, courage, nobility, and independence (eagles do not fly in flocks), the bald eagle is found only in North America, and its image is engraved on the official seal of the United States of America. There were an estimated 100,000 bald eagles in the Unites States in the late eighteenth century when the nation was founded.

The bald eagle nests over most of the United States and Canada, building its aerie, or nest, in mature conifer forests or on top of rocks or cliffs. Its nest is of such a grand size—sometimes as large as a small car—that a huge rock or tree is necessary to secure it. The birds use the same nest year after year, adding to it each nesting season. It is believed that eagles mate for life. Bald eagles prey primarily on fish, water birds, and turtles.

Bald eagles came dangerously close to extinction in the twentieth century, largely due to the pesticide DDT, which was introduced in 1947. Like other carnivorous species, bald eagles ingested large amounts of DDT from poisoned prey. DDT either prevents birds from laying eggs or causes the eggshells to be so thin they are unable to protect eggs until they hatch. The Bald Eagle Protection Act of 1940, which made it a federal offense to kill bald eagles, helped protect the species. However, numbers continued to dwindle and the bald eagle was listed as endangered in 1967.

Bald eagle populations started to recover with the banning of DDT in 1972. The species also benefited from habitat protection and attempts to clean up water pollution. In 1995 the bald eagle was moved from endangered to threatened status on the Endangered Species List. In 2000, surveys showed that there were about 5,800 breeding pairs in the forty-eight contiguous states. The species was proposed for delisting in 1999; that proposal was still awaiting action in 2004.

Aleutian Canada Goose

The Aleutian Canada goose was first placed on the Endangered Species List in 1966, when there were an estimated 800 individuals. The species had been thought extinct for several decades until a remnant population was discovered in 1962 by Fish and Wildlife biologists on a remote Aleutian island. Deterioration of habitat and the introduction of predators such as Arctic foxes and red foxes were blamed for the animal's decline. The goose population rebounded to 6,300 in 1991, and there were well over 35,000 geese by 2002. Conservation efforts included captive breeding, removal of foxes, and relocation and reintroduction of geese to unoccupied islands. The Aleutian Canada goose was officially delisted by the Fish and Wildlife Service in 2001. A graph of population growth over time for this recovered species is shown in Figure 8.6. Table 8.4 shows some of the important events contributing to the recovery of this species.

1750First known introduction of foxes onto Aleutian Islands.
1750–1936Arctic foxes and red foxes introduced to at least 190 islands within the breeding range of the Aleutian Canada goose in Alaska.
1811First complaints from Aleut Natives that foxes had caused severe declines in birds that had once been numerous.
1938–1962Aleutian Canada geese were not found on any of the islands where they historically nested; thought to be extinct.
1962Fish and Wildlife Service biologist found remnant population on remote Buldir Island in the western Aleutian Islands. Population estimated at between 200 and 300 birds.
1963Goslings captured to start first captive flock for propogation.
March 1967The Aleutian Canada goose was officially declared an endangered species under the Endangered Species Protection Act of 1966 (law that preceded the Endangered Species Act).
1971–1991Captive-reared and translocated wild Aleutian Canada geese released on fox-free islands.
1973Passage of the Endangered Species Act.
1973–1984Hunting closures implemented for Aleutian Canada geese on wintering and breeding grounds.
1975Recovery team begins developing formal recovery program. Spring population estimate 790 birds.
Recovery actions implemented including the removal of foxes from breeding grounds on the Aleutian Islands and translocation of geese to unpopulated islands.
1984Geese began to breed successfully on the islands. Foxes removed from four islands.
1990Populations reached 6,300 geese.
December 1990The Aleutian Canada goose was reclassified from endangered to the less imperiled threatened status. Recovery plan was revised, establishing objectives for measuring recovery and indicating when delisting was appropriate.
1990–1998Recovery plans continue to be implemented. Population averages 20% annual growth rate.
1999Populations reach more than 30,000 geese, over four times the original goal for delisting.
July 1999The U.S. Fish and Wildlife Service proposed to delist the species, opening a 90 day public comment period.
Fish and Wildlife Service evaluates comments.
March 2001Fish and Wildlife Service removes the Aleutian Canada Goose from the list of endangered and threatened species. The goose will be managed and protected by the Migratory Bird Treaty Act.
The FWS will continue to monitor the Aleutian Canada goose with the help of the states for five years.
If populations decline significantly, the species can be relisted.
2005If the status remains stable or improves, monitoring is no longer required under the ESA.
source: "Aleutian Canada Goose Road to Recovery," U.S. Fish and Wildlife Service, Washington, DC, 2001 [Online] [accessed June 5, 2002]