D Natural History of Selected Ecological Receptors

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1 D Natural History of Selected Ecological Receptors OY06.06_PT083

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3 Sagebrush-steppe/Grassland Ecosystem HERBIVORES Herbivorous Mammals Sagebrush Vole. The sagebrush vole (Lagurus curtatus) represents the herbivorous mammal guild. It is the palest of the voles and is usually found in the driest places. As the name suggests, its habitat is in scattered sagebrush, loose soil, and arid conditions. It is active day or night and makes shallow burrows close to sagebrush. It feeds on green vegetation, particularly sagebrush, making it an indicator of sagebrush health and habitat adequacy. The vole has an average body weight of 30 grams (g) and breeds a number of times throughout the year, producing four to six offspring per litter (Burt 1980). The sagebrush vole was selected as a measurement receptor of the shrub-steppe grassland ecosystem because it is an important food-source for predators, such as hawks and owls. Also, there is a great deal of knowledge about the meadow vole (e.g., EPA 1993), which is similar to the sagebrush vole in habit and physical characteristics. Washington Ground Squirrel. Native to Oregon, the Washington ground squirrel (Spermophilus washingtoni) is a medium-sized gray squirrel with lighter colored undersides, a black tail, and a tinge of red on hind legs and nose. Three populations are found in the arid desert grasslands and sagebrush of the north-central Oregon counties, Gilliam, Morrow, and Umatilla, and southeastern Washington (ODFW 2000). The Washington ground squirrel typically uses sites for constructing dens where the soil is weaker, deeper, and contain less clay than adjacent unoccupied sites. Ground squirrels are herbivores and depend upon high quality forage and an abundant supply of seeds in order to survive eight months of hibernation. Ground squirrels are important as a prey base for many of their predators of their ecosystems and are important in mixing and fertilization of soils (Johnson and O Neil 2001). The Washington ground squirrel was chosen as the measurement receptor, for the herbivorous guild of the shrubsteppe/grassland ecosystems, because of its important role in these ecosystems and because it a Federal listed endangered species, a State of Washington Candidate Species for listing, and a State of Oregon listed Species of Concern. Pronghorn Antelope. The range of pronghorn antelope (Antilocapra americana) occurs from southern Alberta and southern Saskatchewan, Canada through the western United States to Hidalgo, Baja California, and western Sonora, Mexico. The adult pronghorn antelope weighs from 36 kilograms (kg) to 70 kg. Forbs are its main food source in the summer and browse makes up approximately 80 percent of the winter diet of northern pronghorns. In dry years, browse is eaten in summer as well as in winter. Pronghorns do not drink free water unless the forbs and other vegetation it consumes are low in water. Pronghorns will dig through snow with their forefeet to obtain vegetation in the winter. In the northern part of their range, breeding occurs during a three-week period between mid-september and early October. Its home range ranges from 57 to 1,057 acres and contains a water source, and is often bounded by physical barriers thought to help the male keep female groups inside. The pronghorns ability to consume noxious weeds makes it important in range management (University of Michigan Museum of Zoology 1996). Pronghorn antelopes formally were abundant on the plains of the Columbia River in Oregon until the time of European settlement and were depleted in Washington prior to European settlement (Johnson and O Neil 2001). In 1969, ODFW reintroduced pronghorn antelope to the Umatilla Army Depot as part of a transplant program. The intent was to manage the herd to produce surplus animals for relocation off the depot to preserves. In 2000, ODFW estimated the Umatilla Army Depot population to be 100 to 120 antelope (Tri-City Herald 2000). The pronghorn antelope was chosen as large herbivore measurement receptor species because of its protected status at the Umatilla Army Depot and its important role in controlling noxious weeds. Herbivorous Bird

4 Mourning Dove. The mourning dove (Zenaida macroura) is a common herbivorious bird that is present in the shrub-steppe ecosystem. The average body length of the mourning dove is 10.5 inches (27 cm). Mourning doves occur at greater abundance in shallow soil communities of the shrub-steppe ecosystem (Johnson and O Neil 2001). Seeds, including waste grain from cultivated fields, comprise of over 99 percent of the mourning dove s diet (Ehrlich et al. 1988). Mourning doves also require a source of water; thus, peak abundances occur near rivers. In arid areas, large flocks visit water sources at dawn and dusk (Cornell Lab of Ornithology 1999). The mourning dove is a short distance migrant (Gough et al. 1998) with a home range that extends from across the United States and southern Canada (Cornell Lab of Ornithology 1999). In warm climates, these doves produce up to six broods per year. Typically, two eggs are laid in a nest made in an evergreen tree, although a wide variety of nest sites are used, including clumps of grass. In winter, mourning doves prefer average minimum January temperatures greater than 10 degrees Fahrenheit and may migrate to escape the cold (Cornell Lab of Ornithology 1999). The mourning dove was selected as a measurement receptor to represent herbivorous birds in the shrub-steppe ecosystem because of its prevalence in shrub-steppe and grassland ecosystems, its value to humans as a game species, and its importance in dispersion of seeds for upland vegetation. In addition, the mourning dove is a major prey item for carnivorous mammals, birds, and snakes. OMNIVORES Omnivorous Mammals Deer Mouse. The deer mouse (Peromyscus maniculatus) is an omnivorous mammal present in both the shrub-steppe and riparian food webs. Deer mice are nocturnal and may occupy short-grass prairies, grasssage communities, coastal sage scrub, sand dunes, wet prairies, upland mixed and cedar forests, deciduous forests, and ponderosa pine forests (EPA 1993). They typically have a home range of 0.5 to 3 acres and will burrow in the ground, trees, stumps, and buildings (Burt 1980). EPA (1993) lists a home range of approximately 0.2 to 0.3 acres for adult male and female deer mice within habitats described as Oregon ponderosa pine and Idaho desert. Deer mice average 14.8 grams in weight, and feed on seeds, arthropods, green vegetation, roots, fruits, and fungi. Non-seed plants provide a large proportion of the deer mouse s daily water requirements (EPA 1993). Deer mice normally breed February through November and may have two to four litters per year producing three to five young per litter (Burt 1980). They are prey for hawks and owls (PNL 1993-downs), reptiles, and large carnivorous mammals. The deer mouse was selected to represent the omnivorous mammal because they consume a large amount of food relative to their body weight, which increases their exposure to COPECs, and because they are important in dispersing seeds. Also, due to its burrowing and dietary habits, there is a high potential for direct and indirect exposure with COPECs. Deer mice are also an important food source for predators such as the Western burrowing owl and Western Yellow-bellied racer. The deer mouse was selected because it is an important prey item and because there is a great deal of knowledge about its natural history (e.g., EPA [1993]). Omnivorous Amphibian/Reptiles Western Toad. The western toad (Bufo boreas) is found in many habitats, including desert streams and springs, ponds, lakes, reservoirs, rivers, grassland, woodland, and mountain meadows. It is active at night in warm, low-lying areas and is diurnal at high elevations and in the north. It buries itself in loose soil or seeks shelter in the burrows of gophers, ground squirrels, and other animals. The western toad is active in January through October. Its breeding season occurs from late January through July, depending on latitude, elevation, and local conditions. The range of the western toad extends from north to south from southern Alaska to northern Baja California, and east to west from the Rocky Mountains to the Pacific Coast (Stebbins 1985). The western toad weighs approximately 2.5 g at one year. For adults, about 95 percent of the diet consists of a variety of insects, while tadpoles feed on detritus and algae. Females are observed to travel up to 1.3 miles from breeding sites, and males up to 0.4 miles (Johnson and O Neil 2001). The western toad was as the measurement receptor, for the omnivorous guild of the shrubsteppe/grassland ecosystems because it, along with other shrub-steppe amphibians and reptiles, is very

5 important ecologically because it can contribute disproportionately to biomass production and make large amounts of energy available to other trophic levels (Johnson and O Neil 2001). In addition, the western toad has become locally extirpated for unknown reasons (Johnson and O Neil 2001), and so is considered a sensitive species. The western toad is listed as a Sensitive Species in the State of Washington, as a Vulnerable Species in the State of Oregon, and as a Federal Species of Concern. It was chosen as a receptor species because of its protected status and its important roles as a prey item. Omnivorous Birds Western Meadowlark. The western meadowlark (Sturnella neglecta) is a robin-sized (94.2 g adult female) omnivorous bird found in the shrub-steppe ecosystem throughout the Western United States, as far east as Arkansas (Bull and Farrand, 1994), and is very common in southeastern Washington (Schuler 1988). This bird is one of the most abundant and widely distributed birds in North America. It feeds on a variety of prey, which may include both insects and vegetation (primarily seeds). Bent (1958, as cited in Sample 1997) reports that the western meadowlark s diet consists of approximately 30% plants and 70% insects. The western meadowlark typically lays three to seven eggs in domed shaped nests of grass or weeds concealed in the grass or weeds (Bull and Farrand, 1994). The western meadowlark is an important species within the shrub-steppe ecosystem because it plays an important role in seed dispersal for many grass species and is important prey item for upper trophic level birds. Studies conducted in Southeastern Washington concluded that it was the main bird consumed by the red-tailed, ferruginous, and Swainson s hawks (Rickard 1988). The western meadowlark was chosen as a receptor species because of its important role in seed dispersal and as an important prey item. CARNIVORES Carnivorous Mammal Coyote. The coyote (Canis latrans) is the most common carnivorous mammal present in the shrubsteppe ecosystem. It is also present in the riparian ecosystem and exists throughout North America extending from Mexico to Alaska. The coyote looks like a medium size dog and weighs approximately 15.5 kg. They are chiefly nocturnal, but may be active at all times. Coyotes are primarily carnivorous, feeding on birds and mammals, but they also rely on insects and fruit (Sample 1997). The evidence from studies on stomach and scat contents indicates that there is a seasonal shift in food habits. They sometimes hunt in pairs and are one of the most accomplished predators in the area. Their hunting range is typically ten miles, but may extend to 100 miles. Normally they den in the ground and mate January through February (Burt 1980). The coyote was chosen because it represents an upper trophic level guild in both the shrub-steppe/grassland and riparian ecosystems, giving it a high potential for exposure due to bioaccumulation through the food chain in both habitat types. In addition, it is important in regulating small mammal populations. Carnivorous Birds Peregrine Falcon. The peregrine falcon (Falco peregrinus) is a medium sized raptor weighing approximately 1 kg and having a wingspan of 112 cm. It has a wide range distribution and occurs throughout much of the United States (Federal Register 1999). It prefers open habitats, especially along rivers; and it nests on ledges. Its diet includes a wide variety of birds, especially doves and pigeons, also shorebirds, waterfowl, and passerines (Ehrlich et al. 1988). The peregrine falcon generally reaches breeding maturity at 2 years of age (USFW 1999). In April 2002, the WDFW reclassified the peregrine falcon from state endangered status to "sensitive" because populations of the bird of prey were considered to be recovering (WDFW 2002). In August 1999, the peregrine falcon was delisted as a Federal Species of Concern (Federal Register 1999). The peregrine falcon is currently listed by ODFW with Listed Endangered status (ONHP 2002). It was chosen as a receptor species because of its protected status in the State of Oregon and its important role in regulating the population of other species of birds.

6 Red-Tailed Hawk. The red-tailed hawk (Buteo jamaicensis) is a measurement receptor in the carnivorous bird guild. It is present throughout North America (Bull and Farrand, 1994). Red-tailed hawks are found in habitats ranging from woodlands, wetlands, pastures, and prairies to deserts (EPA 1993). They typically build their nests close to the tops of trees in low-density forests, though they may use cactus, rock pinnacles, ledges or man-made structures when trees are scarce. Trees or other sites for nesting and perching are important requirements for breeding territories and can determine which habitats are used in a particular area. They will lay one clutch a year consisting of one to three eggs. Their home range can vary from a few hundred hectares to over 1,500 hectares. They are opportunistic and prey on whatever is available (EPA 1993). In southeastern Washington, the predominant species that comprises the nesting hawks diet are the yellow-bellied racer, gopher snake, ground squirrel, pocket gopher, cottontail rabbit, black-tailed hare, and meadowlark (Rickard 1988). The red-tailed hawk was chosen as a receptor due to its upper trophic level status and sensitivity to COPECs affecting reproduction. Like the coyote, the red-tailed hawk is a regulator of small mammal and bird species populations. Western Burrowing Owl. The Western burrowing owl (Athene cunicularia hypugaea) is present in open, dry grasslands, agricultural and range lands, and desert habitats (Brown 1996). The Western burrowing owl is a confirmed nester at the UMCD (Dames and Moore 1993). Burrowing owls depend on fossorial mammals both for nest sites and for much of their diet. Burrowing owls nest in the ground in shrub-steppe and can be found nesting in stands of big sage, antelope bitterbrush, or open grasslands. Burrowing owls require deep soils for constructing nests and dens (Johnson and O Neil 2001). Western burrowing owls are opportunistic feeders and feed mainly on large anthropods, small mammals, reptiles and amphibians, bats, and small birds (Brown 1996). The Western burrowing owl was chosen as the measurement receptor for the carnivorous guild of the shrub-steppe ecosystem because of its upper trophic level status and its status as a Federal and State (Washington and Oregon) listed Species of Concern. Carnivorous Reptile Western Yellow-Bellied Racer. The racer (Coluber constrictor) represents a carnivorous amphibian/reptile or the shrub-steppe and riparian food web. It is one of the most common large snakes (49.1 grams) in North America. This snake is plain brown, olive, or bluish above, and unmarked white or pale yellow below. In the West, the subspecies present is the western yellow-bellied racer (C.c. mormorm). The yellow-bellied racer favors open habitats such as meadows, prairies, sagebrush flats, open chaparral, pinon-juniper woodland, and forest glades, and is found in grassy places near rocks, logs, or streambanks. The summer home range averages between 1.8 ha (4.5 acres) for females to 3.0 ha (7.4 acres) for males (EPA 1993). The racer is carnivorous and feeds on a broad range of prey including insects, small mammals, amphibians, reptiles, and birds (Stebbins 1985), but the primary prey for the yellow-bellied racer in eastern Oregon and Washington is the pocket mouse (Rickard 1988). Typically, the yellow-bellied racer will lay a clutch of three to seven eggs sometime between June and August (Stebbins 1985). The western yellow-bellied racer was chosen as a receptor species because it is commonly found in the UMCDF area; its important role in regulating the population of insects, small mammals, amphibians, reptiles, and birds; and the availability of information on the racer (e.g., EPA 1993).

7 Freshwater Ecosystem HERBIVORES Herbivorous Mammal Long-Tailed Vole. The long-tailed vole (Microtus longicaudus) is a herbivorous mammal representative of the herbivorous mammal guild within the riparian ecosystem. It is a rather large vole (body weight 47 g) and as the name suggests has a long tail. It is present throughout the western United States and Canada from New Mexico to eastern Alaska. The long-tailed vole generally inhabits streambanks and brushy areas in the winter. It feeds on grasses, bulbs, and the bark of small twigs. It nests above ground in the winter and burrows in the summer. Young are typically born May to September. The long-tailed vole is an important food source within the ecosystem as prey for raptors, reptiles, and large carnivorous mammals. This small mammal was selected to represent herbivorous mammals in the freshwater ecosystem because it consumes a large amount of food relative to its body weight, which increases its exposure to COPECs. Herbivorous Bird Canada Goose. The Canada goose (Branta canadensis) was chosen to represent the herbivorous bird guild. The Canada goose is a large herbivorous waterfowl that feeds on grains, grass sprouts, and some aquatic vegetation. It is a popular game species and although adapted for life on the water, forages primarily in open fields. Migratory Canada geese leave their breeding grounds during late summer and early autumn; they return in the spring around the time of the ice melting but well before snow cover has disappeared. During the spring and fall migrations and in winter, Canada geese can be found on open water or refuges near grain fields. The home range for the subspecies Great Basin or western Canada goose (B. a. moffiti) in the state of Washington is listed as 290 ha (718 acres) to 2,830 ha (7,009 acres; EPA 1993). The Canada goose was selected to represent herbivorous birds in the freshwater ecosystem because of its important role in seed dispersal, because it is an important game species, and because of its widespread distribution. OMNIVORES Omnivorous Mammal Muskrat. The muskrat (Ondatra zibethica) is a large (2 to 4 pound) rodent that is indigenous and common throughout most of the United States, including the UMCD area, and is found on the edges of ponds, lakes, and streams, and in open water (Burt 1980). The muskrat s habitat is mostly aquatic; though it does move overland, especially in autumn (Burt 1980). The muskrat feeds mostly on aquatic vegetation, and also feeds on crustaceans, frogs, and fish occasionally (Burt 1980, EPA1993). Muskrats are prey for hawks, minks, otters, owls, red fox, dogs, snapping turtles, and water snakes (EPA 1993). Muskrats that live along banks or shores of waterways generally excavate dens in the banks and many vertebrates use muskrat homes for shelter or to find food (EPA 1993). Home range is generally less than 1 ha (2.5 acres), though home range sizes probably depend on quality of habitat. Winter home ranges are mostly of a 15-mile radius. The muskrat was chosen as the measurement receptor because its role as an omnivorous mammal, as prey for primary and secondary predators, as a primary burrow excavator (possibly used by other organisms), and because its relatively small home range (in comparison to skunks and raccoons). Omnivorous Birds Marsh Wren. The marsh wren (Cistethorus palustris) is a common omnivorous bird that inhabits freshwater cattail marshes and salt marshes. It is present throughout the United States from Mexico to Canada (Bull and Farrand, 1994). Their usual habitat includes permanent standing water from several centimeters to nearly a meter deep. Marsh wrens are year-round residents in regions where marshes do not freeze. Marsh wrens consume aquatic invertebrates and other insects including spiders, which they

8 glean from the water surface, stems and leaves of emergent vegetation, and the marsh floor. Many populations of marsh wren are polygynous. Males establish the breeding territories that include both nest sites and foraging areas. The average male territory size for a given year and location can range from ha (0.014 acres) to 0.17 ha (0.42 acres), depending on the habitat and conditions of the year. Nests are generally built 30 centimeters to 1 meter above standing water or high tide. Egg incubation lasts approximately two weeks, as does the nestling period. After fledgling, one or both parents continue to feed the young for about 12 days. Many populations rear two broods per year although some may rear three (EPA 1993). The marsh wren is preyed upon by carnivorous birds, mammals, and snakes. The marsh wren was chosen to represent the omnivorous bird guild because of its role in regulating insect populations, seed dispersal, and as prey for primary and secondary predators. Mallard. The mallard duck (Anas platyrhynchos) is the most abundant duck in the world. It was chosen to represent the omnivorous bird guild. The mallard is found in diverse aquatic habitats including ponds, lakes, and marshes throughout the United States (Bull and Farrand, 1994). Although their diet is omnivorous, 90 percent of their diet may be plant material at some times of the year. Mallards are surface feeders that will often filter through soft mud searching for food items. Mallards frequently interbreed with wild and domestic stock, producing a variety of patterns and colors (Bull and Farrand, 1994). The mallard s home range sizes varied from 66 ha (163 acres) for females to 760 ha (1,882 acres) for pairs (Johnson and O Neil 2001). The mallard was selected as a measurement receptor because of its prevalence in a variety of riparian and aquatic ecosystems, its value to humans as a game species, and its importance in dispersion of seeds for aquatic vegetation. In addition, the mallard is a major prey item for carnivorous mammals, birds, and snakes. Omnivorous Amphibian/Reptile Western Painted Turtle. The western painted turtle (Chrysemys picta bellii) was chosen to represent the omnivorous reptile/amphibian guild. The western painted turtle is the largest of the subspecies of painted turtles (9 to 18 centimeters body length; EPA 1993), and is the subspecies present in the UMCDF assessment area. The range of the western painted turtle includes southwest Ontario and Missouri to the Pacific Northwest (EPA 1993). The western painted turtle overwinters, breeds, and, and forages in water, including ponds, marshes, small lakes, ditches, and streams where the water is quiet or sluggish and the bottom substrate is sandy or muddy (Stebbins 1985 and OSU Press 2001). For winter hibernation or dormancy, the western painted turtle seek deeper water (EPA 1993). Winter hibernation ends in March or April and one to two clutches, of one to twenty eggs, are laid from May to August (Stebbin 1985). The western painted turtle eats aquatic plants, insects, spiders, earthworms, mollusks, crayfish, fish, frogs, and tadpoles (Stebbins 1985). The western painted turtle was selected as a measurement receptor due to its importance as both a predator and prey species, and its ODFW status as a Sensitive-critical Species. CARNIVORES Carnivous Mammals Coyote. The coyote (Canis latrans) is the most common carnivorous mammal present in the shrubsteppe ecosystem. It is also present in the riparian ecosystem and exists throughout North America extending from Mexico to Alaska. The coyote looks like a medium size dog and weighs approximately 15.5 kg. They are chiefly nocturnal, but may be active at all times. Coyotes are primarily carnivorous, feeding on birds and mammals, but they also rely on insects and fruit (Sample 1997). The evidence from studies on stomach and scat contents indicates that there is a seasonal shift in food habits. They sometimes hunt in pairs and are one of the most accomplished predators in the area. Their hunting range is typically ten miles, but may extend to 100 miles. Normally they den in the ground and mate January through February (Burt 1980). The coyote was chosen because it represents an upper trophic level guild in both the shrub-steppe/grassland and riparian ecosystems, giving it a high potential for exposure due to bioaccumulation through the food chain in both habitat types. In addition, it is important in regulating small mammal populations.

9 River Otter. The river otter (Lutra canadensis) represents the carnivorous mammal guild for riparian ecosystems. Depending on availability, otters may consume fish, crayfish, aquatic insects, amphibians, birds, mammals, and turtles. They are found primarily in food-rich coastal areas, such as the lower portions of streams and rivers, estuaries, non-polluted waterways, the lakes and tributaries that feed rivers, and areas showing little human impact. The river otter dens in banks and hollow logs. Its home range, reported to be between 295 ha (731 acres) to 400 ha (991 acres), and encompasses the area needed for reproduction and foraging (EPA 1993). River otters breed in late winter or early spring over a period of three months or more. Birth of a litter follows mating by one year, but implantation is delayed for approximately ten months and active gestation lasts only two months (EPA 1993). Adult males are usually solitary and an adult female and two or three pups make up a typical family unit. Although otters have few natural predators, while on land, they may be taken by coyotes. The otter was selected as a measurement receptor because their piscivorous diet and high trophic level make them a good indicator of bioaccumulation in aquatic ecosystems (EPA, 1993). In addition, they provide an important component to the ecosystem by influencing population dynamics of their prey. Mink. The mink (Mustela vision) is the most widespread carnivorous animal in the North America (EPA 1993). Male minks are 13 to 17 inches (33 to 43 cm) long with a tail of 7 to 9 inches (18 to 23 cm) long. Female minks are 12 to 14 inches (30 to 36 cm) long with a tail of 5 to 8 inches (13 to 20 cm). The male mink weighs 681 to 1,362 grams; the female mink weighs 567 to 1,089 grams. The mink feeds primarily on small mammals, birds, eggs, frogs, crayfish, and fish. It lives in dens along stream or lake banks. The range of the males is several miles along a stream (Burt 1980). Mink are particularly sensitive to polychlorinated biphenyls (PCBs) and similar chemicals, and have been found to accumulate PCBs in their fat to 38 to 200 times dietary concentrations (EPA 1993). Mink were chosen as a measurement receptor because they are widespread, their sensitivity to bioaccumulative chemicals (e.g., PCBs), and because of the availability of natural history information. Pacific salmon. Pacific salmon (Oncorhynchus spp.) are anadromous fishes, which means they spend much of their life feeding in the ocean and migrate to freshwater to breed. There are three species of Pacific salmon and trout associated with the Middle Columbia River and they include chinook (O. tshawytscha) and sockeye (O. nerka) salmon and steelhead (O. mykiss). Steelhead are anadromous rainbow trout. A typical anadromous salmon life history has five main stages: (1) spawning and egg incubation, (2) freshwater rearing, (3) seaward migration, (4) ocean rearing, and (5) return migration. Chinook and sockeye salmon die after spawning. Salmon fry, the life stage during freshwater rearing, typically feed on aquatic insects. The freshwater rearing stage lasts until the fall rains when the salmon migrate to the ocean. Upon completing their freshwater stage, juvenile salmon undergo a physiological change called smoltification so that they can live in saltwater (Johnson and O Neil 2001). The Pacific salmon is an important food resource for humans as well as an important component of the freshwater aquatic ecosystems. The Pacific salmon was chosen as a measurement receptor because of its important role in freshwater ecosystems and because the salmon s early life stages, and most sensitive, occur within the freshwater ecosystems. Carnivorous Birds Peregrine Falcon. The peregrine falcon (Falco peregrinus) is a medium sized raptor weighing approximately 1 kilogram and having a wingspan of 112 cm. It has a wide range distribution and occurs throughout much of the United States. Its migratory habits are variable and some are non-migratory (Federal Register 1999). It prefers open habitats, especially along rivers; and it nests on ledges. Its diet includes a wide variety of birds, especially doves and pigeons, also shorebirds, waterfowl, and passerines (Ehrlich 1988). The peregrine falcon generally reaches breeding maturity at 2 years of age (USFW 1999). In April 2002, the WDFW reclassified the peregrine falcon from state endangered status to "sensitive" because populations of the bird of prey were considered recovering (WDFW 2002). In August 1999, the

10 peregrine falcon was delisted as a Federal Species of Concern. The peregrine falcon is currently listed by ODFW with Listed Endangered status (ONHP 2002). It was chosen as a receptor species because of its protected status in the State of Oregon and its important role in regulating the population of other species of birds. Bald Eagle. The bald eagle (Haliaeetus leucocephalus) is a raptor representing the carnivorous bird guild associated with the riparian habitat. Bald eagles that occur along the Columbia River use trees for daytime perching and, in some cases, communal night roosts (DOE 1996). Bald eagles will remain as far north as the availability of open water and a reliable food supply allow. During the breeding season, eagles require large areas in the vicinity of open water, with an adequate supply of nesting trees. The home range during the spring is estimated to around 3,500 ha (8,669 acres; EPA 1993). Food may vary from spawned salmon and waterfowl in the winter to anadromous and warm-water fishes, small mammals, carrion, and seabirds during the breeding season (WDW, WM, FM, and HMD, 1991). The bald eagle was selected as a measurement receptor because the piscivorous diet and high trophic level make it a good indicator of bioaccumulation in aquatic ecosystems; its federal and state status as a threatened species; its documented nesting sites in Benton County, Washington; and because it is known to be sensitive to COPECs that affect reproduction. Carnivorous Shorebirds Blue Heron. The great blue heron (Ardea herodias) was chosen to represent the piscivorus/carnivorous shorebird guild. They occur near all types of freshwater wetlands including rivers, swamps, marshes, and ditches. They feed mainly in shallow water on fish and frogs, but may feed on small mammals, reptiles, and occasionally birds. Foraging areas may range from 4 to 29 km from the heronry, but most range from four to five km (WDW, WM, FM, and HMD, 1991). The great blue heron breeds throughout North America and winters as far north as southern Alaska (Bull and Farrand, 1994). The herons are colonial breeders that nest near wetlands in tall, mature,deciduous or coniferous trees (Rickard 1988). The blue heron was selected as a measurement receptor because the piscivorous diet and high trophic level make it a good indicator of bioaccumulation in aquatic ecosystems (EPA, 1993). Spotted Sandpiper. The spotted sandpiper (Actitis macularia) is a medium-sized (body weight 37.9 grams) carnivorous shorebird found near ponds, streams, and other waterways. Most sandpipers forage on sandy beaches and mudflats. The spotted sandpiper feeds by probing into the mud and sediment for aquatic insects and worms but will also consume carrion and fish. Year-round resident on the coast of Washington and Oregon. Often in coastal rivers or slightly inland and winters, otherwise spotted sandpipers winter in coastal areas or the southern United States to South America. Female breeding territories were 0.08 ha (0.2 acres) to 2 ha (5 acres); home range sizes vary with nest predation (Johnson and O Neil 2001). Nests are usually placed in semi-open vegetation near the edge of a lake, river, or ocean. Females may lay one to six clutches for different males over one season, averaging 1.3 to 2.7 mates per year. The spotted sandpiper belongs to the family Scolopacidae, which includes numerous shorebirds that feed almost exclusively on small invertebrates. The long-billed curlew (Numenius americanus), is an ODFW- listed sensitive-vulnerable species, and also belongs to the family Scolopacidae. Both the spotted sandpiper and long-billed curlew are known to nest within the UMCD area, including the Umatilla NWR (USFWS 1994). The sandpiper was selected as a measurement receptor for the carnivorous/insectivorous shorebird guild because it has a high potential for exposure through ingestion of a variety of insects, is prey for secondary predators, and also because it is an important migratory bird. The use of the spotted sandpiper as a measurement receptor should be protective of the long-billed curlew. Carnivorous Reptile Western Yellow-Bellied Racer. The racer (Coluber constrictor) represents a carnivorous amphibian/reptile or the shrub-steppe and riparian food web. It is one of the most common large snakes

11 (49.1 grams) in North America. This snake is plain brown, olive, or bluish above, and unmarked white or pale yellow below. In the West, the subspecies present is the western yellow-bellied racer (C.c. mormorm). The yellow-bellied racer favors open habitats such as meadows, prairies, sagebrush flats, open chaparral, pinon-juniper woodland, and forest glades, and is found in grassy places near rocks, logs, or streambanks. The summer home range averages between 1.8 ha (4.5 acres) for females to 3.0 ha (7.4 acres) for males (EPA 1993). The racer is carnivorous and feeds on a broad range of prey including insects, small mammals, amphibians, reptiles, and birds (Stebbins 1985), but the primary prey for the yellow-bellied racer in eastern Oregon and Washington is the pocket mouse (Rickard 1988). Typically, the yellow-bellied racer will lay a clutch of three to seven eggs sometime between June and August (Stebbins 1985). The western yellow-bellied racer was chosen as a receptor species because it is commonly found in the UMCDF area, its important role in regulating the population of insects, small mammals, amphibians, reptiles, and birds, and the availability of information on the racer (e.g., EPA 1993).