Atlantic coast joint venture waterfowl implementation plan
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4. WATERFOWL POPULATION STATUS AND TRENDS The Atlantic Coast of North America supports a diverse array of migrating and wintering waterfowl species. A total of 41 species of native waterfowl are known to be found in the ACJV at some time during the year, two of these species are restricted to Puerto Rico. Twenty-five species are known to breed within the Atlantic Coast Joint Venture (Table 2.2). Of the less numerous waterfowl species, mottled ducks are common residents in Florida and South Carolina with a growing population along the coast of Georgia. Small numbers of fulvous whistling ducks are present in Florida and Georgia during the winter. 4.1 Breeding Populations The ACJV provides breeding habitat for 25 species including black ducks, mallards, wood ducks, mottled ducks, and small numbers of other waterfowl species (Table 2.2). Numbers of breeding waterfowl in the Atlantic Coast have been estimated in the past primarily through the North American Breeding Bird Survey. Within the past 10 years, however, coordinated surveys specifically for breeding waterfowl have been conducted from the mid-Atlantic states northward into Maine and in the eastern provinces of Canada. Trends in wood duck populations still are monitored through the Breeding Bird Survey. Since 1989, breeding population estimates for mallards and other waterfowl (not separated) are compiled for the northeastern U.S. in conjunction with the July Production and Habitat Survey. Contributing states include all or portions of Delaware, Connecticut, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont (U.S. Fish and Wildl. Serv. 2004). As of 2004, Mallards had shown a non-statistically significant decrease in their population in the northeastern part of the ACJV (Table 4.1). The eastern survey area, strata 51-56, was established in 1990 to estimate the breeding population in eastern Canada of the 10 most common species that breed in eastern North America and winter along the Atlantic Coast. These include mallards, black duck, gadwall, wigeon, green-winged teal, ring-necked duck, goldeneye, bufflehead, and Lesser Scaup, goldeneye (undifferentiated) and mergansers (undifferentiated). In 1995 Maine was included as stratum 62 of the eastern survey area (U.S. Fish and Wildl. Serv. 1997). Current population estimates show all species maintaining relatively stable breeding populations during this period (Table 4.1). The only statistically significant decrease was observed in the undifferentiated mergansers. Within the past 20 years resident populations of giant Canada geese have become prevalent within all states of the ACJV. Many populations have readily adapted to the extensive urban and suburban development along the Atlantic Coast states and, thus, have created many nuisance problems for state agencies. Also, the proliferation of resident Canada geese has confounded the ability to monitor populations of migratory Canada geese during the mid-winter surveys. These resident populations provide additional hunting opportunity in most Atlantic Flyway states. However, use of hunting in reduction and control of some of these resident populations is difficult due to the location of many flocks in residential areas, which promotes high survival and little hunting mortality. Thus, alternate methods of control to reduce nuisance complaints have been employed which includes constant harassment by air cannons or dogs, ‘round-ups’ and relocation during molting, and spraying lawns and golf course greens with aversive agents. Table 4.1. Breeding population estimates for waterfowl from the Waterfowl Breeding Population and Habitat Survey (WBPHS Stratum 62, Maine) and from the Northeastern States Plot Survey (Includes all or portions of CT, DE, MD, MA, NH, NJ, NY, PA, RI, VT, and VA). Trends were calculated from log-transformed (ln) population estimates for 10 years in Stratum 62 (1995-2004), and for 12 years of the Northeastern Plot Surveys (1993 – 2004). Some species are not differentiated in the May breeding, Stratum 62, due to difficulties in identification from the air. Blank cells indicate no population estimate was available for a particular species-survey combination. Data obtained from Migratory Bird Management Office of the U.S. Fish and Wildlife Service, 2004.
NS – P > 0.05 * - 0.01 < P 0.05 ** - 0.001 < P 0.01 *** - P 0.0001 1 – Undifferentiated species 4.2 Wintering Populations In an analysis of recent Mid-Winter Survey (MWS) data (1970-2003) trends were calculated for 21 species or species groups (e.g., undifferentiated scoters) (Table 4.2). All indices were log-transformed (ln) prior to conducting a simple linear regression to test for long-term trends in MWS indices. Of the 20 species/species groups, eight showed statistically significant decreases (American Black Duck, American Wigeon, Canvasback, Common Goldeneye, Long-tailed Duck, Mallard, Northern Pintail, and scoters [undifferentiated]). Six species showed statistically significant increasing trends (Brant, Bufflehead, merganser [undifferentiated], Ring-necked Duck, snow goose [undifferentiated] and Tundra Swan). The remaining seven species had trends that were not statistically significant indicating an absence of directionality. American Black Duck populations continue to be a major concern in the ACJV. The majority of the continental population winters along the Atlantic Coast of the U.S. and Canada (U.S. Fish and Wildl. Serv. 1988). Black ducks have been declining about 3% per year since the 1950s based on the Mid Winter Survey (Longcore et al. 1998, McAuley et al. 1998, see Table 4.2 for recent analysis of these data). Schools of thought differ as to the reason for the decline of black ducks. These include hybridization with mallards, excessive harvest, and continued habitat degradation through loss of habitat and increased disturbance from development adjacent to important wintering areas and potential chemical contamination of important wintering areas. Although harvest restrictions were implemented in 1983 and the continental population in the MWS appears to have stabilized (Longcore et al. 1998, McAuley et al. 1998), mid-winter indices of black ducks are well below the objective established by NAWMP. Populations appear to have stabilized only in the ACJV at approximately 223,800 birds (average MWS count from 1990-2003). Counts in the Mississippi Flyway were at all time lows, 37,400 in 1997 (U.S. Fish and Wildl. Serv. 1997). Recently, much concern has been directed at sea ducks in the Atlantic Flyway which includes common eiders, oldsquaws, scoters (all 3 species), and harlequin ducks. Traditionally, sea ducks have been hunted in both the regular duck season and a special sea duck season which has been long (107 days) with liberal bag limits (7 birds) and within a sea duck zone, which varies among states. Status of sea ducks was evaluated for the first time in 1993 by the Office of Migratory Bird Management and 1994 by the Atlantic Flyway Technical Section. Only recently, in 1998, have the special sea duck seasons been reviewed (Caithamer et al. 1998, unpubl. rep.). Because of the paucity of information on population dynamics and the effects of hunting on sea ducks, trends in sea duck populations have been difficult to detect. However, in 1993 the Atlantic Flyway Council and the U.S. Fish and Wildlife Service restricted scoter harvests in response to population indices that showed decreasing populations. Also, low numbers of harlequin ducks have prompted Canada to list the species as endangered in eastern Canada and they are listed as threatened by the state of Maine. In response to the growing concern for sea duck populations and equivocal and weak conclusions based on traditional, long-term population monitoring techniques, a Sea Duck Joint Venture (SDJV) has been formed to address the issues surrounding sea duck ecology and population management. Currently, the ACJV and SDJV are funding efforts to develop new sampling protocols for developing a robust method for estimating wintering populations of sea ducks along the Atlantic Coast. Table 4.2. Linear regression analyses of Midwinter Survey data, 1970 - 2003, for the ACJV portion of the Atlantic Flyway. Data were log-transformed (ln) prior to analyses. Wood Duck was dropped from these analyses due to inconsistent time-series in the Mid-winter Survey.
NS – P > 0.05 * - 0.01 < P 0.05 ** - 0.001 < P 0.01 *** - P 0.0001 1 – Combines four populations (North Atlantic, Atlantic, Atlantic Flyway Resident, Southern James Bay) that are managed separately. 2 – Undifferentiated mergansers 3 – Undifferentiated scaup 4 – Undifferentiated scoters 5 – Combines Greater and Lesser Snow Goose populations; may include some individuals of Ross’ Goose 5. THREATS TO THE CONSERVATION OF WATERFOWL IN THE ACJV Threats facing waterfowl in the ACJV vary by species and geographic area but can be grouped into general categories that include habitat loss, fragmentation and degradation, contaminants, over-harvest, genetic introgression with congenerics, nest predation, and mortality from commercial fisheries (broadly defined to include interactions with aquaculture). Although none of these factors are unique to the ACJV, the large and increasing human population found within the joint venture boundary increase the frequency and severity of these threats (see section 5.4). 5.1 Habitat Loss, Fragmentation and Degradation Of the threats mentioned, habitat loss, fragmentation and degradation are the ones threatening the largest number of waterfowl species in the ACJV. Although the rate of wetland loss has decreased, loss of wetlands remains a major concern across the ACJV. Between the 1970s and 1990s approximately 918,000 ha (2,268,418 acres) of wetland habitat was lost or converted in the ACJV (Table 3.1, Koneff and Royle 2004), an average loss of approximately 45,900 ha per year (113,421 acres per year). Several waterfowl species (e.g., Canvasback, Redhead and Tundra Swan) that winter in the ACJV are dependent on the presence of submerged aquatic vegetation (SAV) beds along the coast of the mid-Atlantic region. For example, it has been estimated that SAV once covered more than 80,900 ha (200,000 acres) of the Chesapeake Bay; as of 2003 an estimated 26,187 ha (64,709 acres) of SAV beds remained in the bay, a loss of seventy percent (http://www.chesapeakebay.net/info/baygras.cfm#SAV%20Decline). Such declines can have a dramatic impact on wintering waterfowl populations. Historically, an estimated 80,000 Redheads used this resource in the Chesapeake Bay. Today only a few thousand individuals are found annually (U.S. Fish and Wildlife Service, 19??). The causes of these declines are well documented and include declining water quality, disease, direct disturbance to SAV beds, and alteration of shallow water habitats. Mute Swan, an invasive species with an increasing population in the ACJV, also is responsible for further degradation of SAV beds in the mid-Atlantic region. A regional habitat threat facing several species of waterfowl (e.g., Common and Hooded Mergansers, Common Goldeneye and Wood Duck) that breed in the ACJV is a reduction in availability of natural cavities (Dugger et al. 1994, Eadie et al. 1995, Hepp and Bellrose 1995, Mallory and Metz 1999). This is mainly the result of changes in silvicultural practices that favor shorter rotations (i.e., the interval between harvests) and snag removal due to safety concerns. The results of such practices are younger forests with fewer trees of the size and age class necessary to have naturally occurring nest cavities. The effect of this threat is more pronounced in the Southeast and is not perceived as a concern in the Northeast due to the more mature successional stage of the forests in this region (E. Robinson, pers. comm.). Although wildlife managers have known for years that nest boxes are an effective management tool to counter the loss of natural cavities, their installation and maintenance is expensive and time-consumptive so this management option is unlikely to completely offset the loss of natural cavities. Degradation of near-shore and off-shore habitats from commercial fisheries and increasing aquaculture is of increasing concern especially along the northern coast of the ACJV. Species thought to be susceptible to these impacts include: Long-tailed Duck, Common Eider, Harlequin Duck, Surf Scoter and Atlantic Brant (Reed et al. 1998, Savard et al. 1998, Robertson and Goudie 1999, Goudie et al. 2000, Robertson and Savard 2002). Although the level of effect has not been quantified, it is expected that the impact of these activities will increase given the current governmental policies to expand aquaculture and increasing reliance of commercial fisheries on non-traditional species. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||