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American Woodcock
Source: U.S. Geological Survey's (USGS) Biological Resources Division report: The Status and Trends of the Nation's Biological Resources (Detailed source information is at bottom of page.) For more information:
The American woodcock is a shorebird that inhabits forested areas from Manitoba east to Newfoundland and Labrador and south to the Gulf of Mexico. It is known by a variety of colorful local names including timberdoodle, Labrador twister, brush snipe, woods snipe, and bog sucker. The woodcock is a popular game bird throughout eastern North America and is the object of an estimated 3.4 million days of recreational hunting annually (U.S. Department of the Interior 1990). Hunters in the United States harvest an estimated 1.1 million woodcock annually (Straw et al. 1994), making woodcock among the top ten species of migratory game birds harvested in the Atlantic and Mississippi flyways. The most distinctive features of the woodcock are its long bill (60-75 millimeters), which is specialized for feeding on earthworms, and its large eyes, which are set far back for 360o vision (Keppie and Whiting 1994). Woodcock are cryptically colored and more compact than other shorebirds. Females are larger than males, with female weights ranging from 151 grams to 279 grams, and males from 116 grams to 219 grams (Mendall and Aldous 1943; Owen and Krohn 1973). Their plumage consists of a mottled pattern of browns, black, buff, and gray. Short powerful wings allow them excellent maneuverability when flying through the thickets and tangled brush where they live (Fig. 1).
The northeastern states are a major breeding area for woodcock. Most woodcock winter south of the region except for a small population along coastal Virginia. Cape May, New Jersey, and Cape Charles, Virginia, are major staging areas for woodcock during migration, especially in the fall. Birds arrive in the Northeast from wintering areas as early as February in some states, but the peak of the breeding season is in April and May. These birds are probably the earliest nesters among ground-nesting species in North America. Around dawn and dusk during the breeding season, males of this secretive species come out of hiding to perform a spectacular display. Courtship begins with a ground display during which the male turns and utters a nasal "peent" for about a minute. This is followed by a 45- to 60-second aerial display in which the male spirals 30 to 90 meters above the ground while creating a distinctive twittering sound with the outer three wing primaries. The display ends with a melodic warbling call during the descent. After the bird alights at the takeoff point, the sequence is repeated (Mendall and Aldous 1943; Straw et al. 1994). Courtship bouts last 25-45 minutes, depending on duration of twilight, but may continue throughout the night during periods of bright moonlight. Habitat requirements of woodcock vary with activity, time of day, and season. Woodcock spend the daylight hours using their long bills to probe for earthworms, which make up nearly 80% of their diet (Sperry 1940; Keppie and Whiting 1994). They rely on their cryptic coloration and the dense vegetation to hide them from predators. At dawn and dusk they fly from the protection of their daytime cover to fields and openings to roost, feed, or mate. They are not restricted to specific plant assemblages (Keppie and Whiting 1994) as long as the habitat provides the necessary stem density and structure (Straw et al. 1994). The birds prefer early-successional habitats created by periodic disturbance of the forest; optimal habitat is provided by dense hardwood cover on good soils with an abundance of earthworms (Straw et al. 1994). Thus, young forests and abandoned farmland mixed with forested land are ideal woodcock habitat (Keppie and Whiting 1994). Woodcock use forest openings, clear-cuts, fields, roads, pastures, and abandoned farmland as display areas (singing grounds) for courtship (Mendall and Aldous 1943; Liscinsky 1972). Vegetative composition of the singing ground varies locally and throughout the range and is probably unimportant as a determinant of use (Dwyer et al. 1988; Sepik et al. 1993). More likely the quality of the adjacent habitat for nesting and brood-rearing determines use by males. Young aspen, birch, hawthorn, alder, and dogwood provide appropriate cover in the Northeast (Keppie and Whiting 1994; Straw et al. 1994). Nests and broods are found in young to mixed-age forests, but young, open, second-growth stands are preferred (Mendall and Aldous 1943). In areas where habitat is managed, woodcock select stands of young hardwood regeneration (Gregg and Hale 1977; McAuley et al. 1996). During summer, young hardwoods and mixed woods with shrubs, particularly alders less than 20 years old, provide daytime cover for feeding (Morgenweck 1977; Rabe 1977; Hudgins et al. 1985). Woodcock are sometimes found in stands of mature forest, but only if there is a dense understory (Sheldon 1967; Rabe 1977). In the Northeast, woodcock rarely use conifer stands, except during drought when they may be critical for survival (Sepik et al. 1983). On summer nights, many birds roost in clearings, such as blueberry barrens, pastures, recently harvested woodlands, and plantations (Dunford and Owen 1973; Sepik et al. 1981; Sepik and Derleth 1993). Woodcock use many of these same fields as singing grounds in the spring. In the fall and during migration, woodcock spend the days in young, moist hardwoods with shrub understories (Keppie and Whiting 1994), whereas in winter they use a variety of habitats during the day, especially bottomland hardwoods, upland mixed pine-hardwoods, and recently burned stands of longleaf pine (Glasgow 1958; Britt 1971; Dyer and Hamilton 1977). Woodcock are managed on the basis of two regional populations, the eastern and the central (Owen et al. 1977); northeastern states are part of the eastern management unit. Analysis of band recovery data indicates that little crossover of birds occurs between the regions (Martin et al. 1969; Krohn et al. 1974). Furthermore, regional boundaries conform with the boundary between the Atlantic and Mississippi waterfowl flyways. Reliable indices of population size, productivity, harvest size, and distribution of woodcock are difficult to obtain (Bruggink and Kendall 1995). Because of their small size, cryptic color, and preference for dense vegetation, woodcock cannot be censused. The status of the woodcock population is now monitored with a wing-collection survey and the singing-ground survey. The wing-collection survey was developed in the 1960's to monitor productivity. Cooperating woodcock hunters and some waterfowl hunters who hunt woodcock provide wings from birds that they shoot (Bruggink and Kendall 1995). Hunters are also asked to record the effort and success of their hunts. Age and sex of the birds can be determined from plumage characteristics (Martin 1964), and the ratio of immature birds to adult females in the survey sample provides an index of recruitment. The recruitment index for woodcock in the eastern region for 1995 (1.4 immatures per adult female) was higher than in 1994 but was 17.6% less than the long-term average of 1.7 immatures per adult female (Bruggink and Kendall 1995; Fig. 2), indicating poor production of young in recent years, although these numbers should be interpreted with caution (see Owen et al. 1977 and Straw et al. 1994). A major problem of the wing-collection survey is that it is not random, because no comprehensive sampling frame exists for woodcock hunters. When the U.S. Fish and Wildlife Service's Harvest Information Program is implemented, this framework will be provided. Under this program, states will provide the U.S. Fish and Wildlife Service with a computerized address list of everyone who purchases a hunting license, allowing for a true random selection of hunters for the survey.
Researchers developed the singing-ground survey to count displaying males during the breeding season. Since 1968 randomly chosen roadside routes have been surveyed for "singing" male woodcock to provide an index of the population size. Routes were established along lightly traveled secondary roads in the central and northern portion of the breeding range. The survey consists of approximately 1,500 routes, each 5.8 kilometers long and consisting of 10 listening points. Recent (1985-1995) and long-term (1968-1994) trends in the singing-ground survey suggest that woodcock populations have declined at an annual rate of 2.0% recently and 2.4% long term in the eastern region (Fig. 3). Populations in the central region declined an average of 2.8% annually from 1985 to 1995 and an average of 1.4% per year from 1968 to 1994 (Bruggink and Kendall 1995). In every state in the Northeast except New Hampshire, the number of males heard on the singing-ground survey has declined (Bruggink and Kendall 1995).
The major causes of the long-term decline in woodcock populations are not known but probably result from degradation and loss of suitable habitat on both the breeding and the wintering grounds (Owen et al. 1977; Dwyer et al. 1983; Straw et al. 1994). Researchers have associated habitat loss with urbanization and forest succession on the northern breeding areas and with drainage and land-use conversion on the wintering grounds (Straw et al. 1994). Although forests cover 60%-90% of New England (Brooks and Birch 1988; Waddell et al. 1989) and northern New England is at least 75% forested (DeGraaf et al.1993), the forests of the Northeast are aging. New England forests are currently dominated by saw timber-sized trees, whereas the early successional seedling-sapling stands that woodcock require are becoming regionally scarce. As of 1988, young stands made up only 8% of the timberland in New England (Brooks and Birch 1988), a trend consistent throughout the Northeast (Fig. 4). The decline in young forest is the result of changing management objectives and techniques, changing attitudes of landowners, a decline in farm abandonment, increased fire suppression, and increased urbanization (Brooks and Birch 1988; U.S. Fish and Wildlife Service 1996). Thus, most changes in the timberland resources of this region have resulted from changes in forest structure and not from gains or losses in acreage. Most woodcock habitat in the Northeast is privately owned; timber companies control the next largest portion of this resource, and state and federal agencies control the smallest portion (U.S. Department of the Interior 1990). State and federal governments and private agencies need to determine ways to stimulate creation of woodcock habitat on private lands.
To increase the woodcock population, the U.S. Fish and Wildlife Service has developed an American Woodcock Management Plan (U.S. Department of the Interior 1990). In the Northeast, the management goal (U.S. Fish and Wildlife Service 1996) is to restore woodcock populations to 1985 levels by the year 2005. Conservation and management of woodcock habitat are critical to achieving these population objectives. Habitat management that promotes early successional forest types increases local breeding populations of woodcock and other wildlife. Crucial to this effort is encouraging commercial timber companies to incorporate woodcock habitat management into their timber-management activities and to inform private landowners of potential habitat-management opportunities on their lands. In addition, identification and management of woodcock wintering habitat are also necessary. Most importantly, cooperation in habitat management among state, federal and nongovernment organizations, and private citizens will be necessary to reverse the downward trends of the woodcock population. Although available data do not indicate that hunting has played a major role in woodcock population declines, proper management requires that we understand the relationship among hunting regulations, harvest, and woodcock populations, especially at the local level (Straw et al. 1994). Implementation of the Harvest Information Program will be the first step in determining this relationship. Research into the effects of hunting on local and regional populations is also necessary, but few studies are under way on woodcock in the Northeast. Likewise, research is needed to address the potential effects of new pesticides on woodcock, their habitat, and earthworms; such research has not been done for 15 years. Source details: |
