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A. Collisions

Collisions with moving vehicles is a widespread source of waterfowl mortality for which there are few quantitative data (Stout and Cornwell 1976). Roadsides provide prime duck-nesting habitats in many areas (Oetting and Cassell 1971, Higgins 1977). Sargeant (1981) estimated that the breeding season mortality of dabbling ducks in North Dakota from collisions with vehicles averaged only 0.2% of the size of breeding population and that diving ducks were less susceptible to such collisions than were dabbling ducks.

Broods crossing roads are also subject to collisions with vehicles, but we found no studies that quantified this source of mortality. Flightless adult Canada Geese with their goslings were commonly killed while crossing a highway that separated their marsh roost areas from grazing areas at Lower Klamath National Wildlife Refuge, California (D. G. Raveling, personal observations). Similar mortality in Michigan was noted by Sherwood (1968).

Collisions with farm machinery cause mortality of ducks in certain upland habitats in agricultural areas. As many as 2-20% of female ducks (mostly dabbling ducks) nesting in fields at time of hay-cutting have been killed by mowing machines (Labisky 1957, Milonski 1958, Moyle 1964). However, Johnson and Sargeant (1977) concluded that the overall mortality of female Mallards in North Dakota from hay-cutting was minor because of the relatively small amount of land devoted to raising hay. Effects in areas where a greater portion of nests occur in hay fields (e.g., southern Wisconsin [Gates 1965], Rainwater Basin area of Nebraska [Evans and Wolfe 1967]) could, of course, be greater.

Waterfowl eggs in hayed or tilled croplands are highly vulnerable to mortality associated with hay-cutting or tillage operations. Nearly all active duck nests in hay fields at time of cutting are destroyed either directly or indirectly (increased exposure to predators) by the disturbance (Bennett 1938, Labisky 1957, Moyle 1964). Hay-cutting was a major source of egg mortality of Mallards in southern Wisconsin (Gates 1965) and of Northern Pintails in the Rainwater Basin area of Nebraska (Evans and Wolfe 1967). Klett et al. (1988) estimated that duck nest success was only 7% in cultivated cropland in the prairie-parkland region of North Dakota, where machines and predators destroyed 37% and 54% of nests, respectively. Although cropland composed from 57% to 80% of available habitat in the areas studied by Klett et al. (1988), it was seldom used for nesting by waterfowl, except by Northern Pintails, which initiated over 50% of their nests in cropland (also see Milonski 1958).

Collisions with farm machinery have not been identified as an important source of mortality among prefledged waterfowl, but many newly hatched young are likely killed during haying and tillage operations.

B. Weather

Spring snowstorms are common in northern nesting areas. A severe early April snowstorm that froze many eggs of Wood Ducks nesting in structures, and presumably in natural cavities, contributed to significantly reduced Wood Duck production in Massachusetts in 1982 (Heusmann 1984). In the prairie-parkland region the early-nesting Mallard and Northern Pintail are most vulnerable to such storms, but direct mortality is uncommon (Keith 1961, p. 58; Dane and Pearson 1971). Unless spring storms are unusually severe, their detrimental effects on prairie-parkland nesting waterfowl, most of which renest, are probably outweighed by benefits derived from the additional meltwater. However, Krapu (1977) pointed out that spring snowstorms can result in increased losses of Northern Pintail recruitment by delaying tillage operations in agricultural fields until most Northern Pintails have initiated incubation.

In arctic areas, snowstorms during nesting can have severe effects on waterfowl production because of limited or no renesting potential. For example, Barry (1967) observed a particularly violent wind and snowstorm near the time of hatching at the Anderson River Delta, Northwest Territories, that resulted in losses of about 100%, 75%, and 50% of remaining Snow Goose, White-fronted Goose, and Brant nests, respectively. Barry (1968) also estimated that a severe May storm and ice conditions in the Beaufort Sea of northern Alaska and Canada resulted in death, largely through starvation, of an estimated 100,000 King Eiders in 1964.

Severe hailstorms that kill waterfowl occur occasionally in the prairie-parkland region, usually late in the breeding season. Smith and Webster (1955) recorded the effects of two of the most severe hailstorms in Alberta's history. Those storms, which occurred in July 1953, together affected 2,700 km² and killed an estimated 64,000-148,000 adult and juvenile waterfowl. Numerous dead, but no live, waterfowl were found on ponds examined after the storms passed. Other hailstorms that likely had a severe effect on local waterfowl populations were reported for Saskatchewan, Minnesota, and North Dakota (e.g., Fyfe 1957, Moyle 1964, Piehl 1979).

Flooding affects waterfowl eggs in many areas. Nests in riverine systems, impoundments, estuaries, and certain landlocked lakes, where water from surrounding areas can collect rapidly, are especially vulnerable to flooding (e.g., Williams and Marshall 1938, Dow 1943, Wolf 1955). Most waterfowl species that nest in sites subject to flooding cope with gradual increases in water levels by choosing higher, drier sites or by building nests higher as water levels rise (e.g., Wolf 1955, Hilden 1964, Bellrose 1980). Also, because eggs of waterfowl species are cold-hardy (Batt and Cornwell 1972), exposure to cold temperatures, such as from flooding and freezing, does not necessarily result in mortality (e.g., Greenwood 1969, Hansen et al. 1971, Ely and Raveling 1984). The threat of catastrophic tidal floods exists in some arctic areas where populations of certain waterfowl such as Brant and eiders may be concentrated in low-lying coastal zones (Hansen 1961). Such storms are uncommon and usually occur after most waterfowl nests have hatched (Hansen 1961), but in a given year or location, floods may destroy nearly all the potential production of waterfowl in tidal zones (Glover and Smith 1963, King 1965 in Eisenhauer and Kirkpatrick 1977). Even species that nest in relatively secure sites may occasionally suffer large losses from severe tidal floods. For example, Ely and Raveling (1984) reported that tidal floods were responsible for destruction of 48% of White-fronted Goose nests in one year on their study area on the Yukon-Kuskokwim Delta, Alaska.

For obvious reasons, eggs of species that nest in trees and on ground away from shorelines are relatively secure from flooding. Only about 2% of many thousands of nests of dabbling ducks examined in the prairie-parkland region were destroyed by flooding (Smith 1971, Stoudt 1971, Canadian Wildlife Service and U.S. Fish and Wildlife Service 1987, Klett et al. 1988). Moreover, flooding has not been a major cause of egg mortality in most studies of ducks that nest over water (mostly diving ducks) (see species accounts in Bellrose 1980). Only 16% of losses of nests in an 18-year study of Ring-necked Ducks in Maine (Mendall 1958) and 6% of nest destructions in a 12-year study of Canvasbacks in Manitoba (Stoudt 1982) were attributed to flooding.

The greatest proximate effect of weather on waterfowl mortality appears to be on prefledged young, especially in northern areas where young are often exposed to adverse weather soon after hatching. Heavy rain during brood rearing (MacInnes et al. 1974) and a snowstorm coinciding with the peak of hatch (Raveling 1977) in Canada Geese were suggested as causes of heavy losses of goslings.

Young waterfowl are vulnerable to chilling during the first few days after hatching (Koskimies and Lahti 1964, Marcstrom 1966, Untergasser and Hayward 1972); hence, females of most waterfowl species brood their young (e.g., Cain 1972, Mendenhall 1979). The northern limits of distribution of Black-bellied Whistling Ducks may be determined by cold temperatures (Cain 1973). Although feeding by newly hatched young can be delayed for a few days without mortality (Weller 1964, Kear 1965, Ankney 1980), food must be found before stored energy reserves are depleted. Any factor that stresses young, such as excessive cold or heat, especially during the first few days after hatching, will likely result in higher mortality.

C. Predation

The impact of predation on waterfowl populations during the breeding season has been repeatedly revealed in studies where predators have been removed or introduced. Removal or exclusion of predators from duck breeding sites in the prairie-parkland region has resulted in substantial increases in duck production (e.g., Balser et al. 1968, Duebbert and Lokemoen 1980, Lokemoen et al. 1982, Glup and McDaniel 1988). Provision of predator-proof nest sites for Black-bellied Whistling Ducks (Bolen 1967), Canada Geese (Brakhage 1965, Krohn and Bizeau 1980), Wood Ducks (Bellrose et al. 1964), and Mallards (Bishop and Barratt 1970, Doty et al. 1975) has increased nest success in numerous areas. Waterfowl on oceanic islands, many of which have evolved in the absence of ground-dwelling predators, have been severely affected by introductions of predators (Weller 1980). The release of arctic foxes on islands in the Aleutian archipelago resulted in the near extinction of the Aleutian Canada Goose (Murie 1959 , Springer et al. 1978). Arctic foxes have also had a major influence on the distribution and abundance of Common Eiders and King Eiders in Greenland (Larson 1960, Meltofte 1978), of Common Eiders in Alaska (Schamel 1977), and of Snow Geese on Wrangel Island, USSR (Syroechkovskiy 1972).

Natural events that alter environments can result in changes in predator communities and provide increased opportunities for contact between predators and waterfowl. The severe 1964 earthquake in Alaska that uplifted the outer portion of the Copper River Delta by about 2 m greatly altered the nesting habitat and associated predator community in areas inhabited by Dusky Canada Geese (see review in Cornely et al. 1985b and Table 12-2). Following the earthquake, vegetation communities changed, and brown bears and coyotes invaded the Delta; in some years they destroyed up to 80% of the Dusky Canada Goose nests. The increased predation is believed to be a prominent factor in the recent decline in numbers of this subspecies of Canada Goose.

Adult swans and geese, because of their large size and generally aggressive behavior, are prey of few predator species. Canids are probably the most important predators of these large waterfowl, although Golden Eagles and Snowy Owls take some breeding adult geese (Barry 1967). Arctic foxes or red foxes are common throughout much of the arctic, but they are regarded as only occasional predators of adult geese (Barry 1967, Ryder 1967, Mickelson 1975). Dow (1943), Sherwood (1968), and Hanson and Eberhardt (1971) reported that coyotes killed a few nesting Canada Geese in their studies in California, Michigan, and Washington, respectively, but coyotes are absent from nearly all arctic and subarctic regions (Hall 1981), where most swans and geese nest. Raveling and Lumsden (1977) documented one instance of predation by a gray wolf on an incubating Canada Goose in their study at the Hudson Bay lowlands of Ontario.

Adult ducks in North America are killed by many predator species, especially red foxes (Reed 1975b, Sargeant et al. 1984), mink (Eberhardt and Sargeant 1977, Arnold and Fritzell 1987), long-tailed weasels (Keith 1961), Great Horned Owls (McInvaille and Keith 1974), and several species of hawks (McInvaille and Keith 1974, Blohm et al. 1980, Schmutz et al. 1980, Dekker 1987). Coyotes, if abundant, are probably major predators of adult ducks in some areas (A. B. Sargeant, unpublished data).

Vulnerability to red fox predation is greater among dabbling ducks than diving ducks and greater among females than males (Sargeant et al. 1984). However, even careful examination of depredated nests often fails to reveal the extent of depredation on females, because they may be captured without struggle and carried off before being eaten (Sargeant and Eberhardt 1975, Sargeant et al. 1984).

Adult diving ducks appear to be less vulnerable to predators than adult dabbling ducks, because most species tend to nest over water, where they are relatively secure from terrestrial predators (Sargeant et al. 1984). Mink, however, occupy aquatic habitats throughout North America (Hall 1981). Mink are potentially severe predators of female ducks that nest over water and of brooding females (Eberhardt and Sargeant 1977, Talent et al. 1983, Cowardin et al. 1985, Arnold and Fritzell 1987). Introduced mink were considered responsible for practically eliminating some concentrations of breeding ducks on islands of Lake Myvatn, Iceland (Gudmundsson 1979).

In general, predators exert their greatest influence on waterfowl populations by preying on eggs. Predation, usually from several species, is the major source of egg mortality in nearly all studies of waterfowl nest success (Tables 12-2, 12-3).

Predation is also believed to be a major cause of mortality of prefledged waterfowl (Tables 12-4, 12-5), but for reasons previously discussed, both the magnitude and true effect of predation are seldom determined. Predation can be a powerful force in culling out weakened or stressed young waterfowl that may be unlikely to survive in the absence of predation. This type of mortality has been associated with effects of adverse weather (Mendenhall and Milne 1985), diseases (Milne 1974, Mendenhall and Milne 1985), overcrowding (Koskimies 1954, Newton and Campbell 1975), physical inferiority (Cooch 1961), and possibly contaminants (Hunter et al. 1984, Grue et al. 1986). However, it should not be assumed that a major portion of predation on prefledged waterfowl is linked to the above factors and, therefore, of little consequence. Although many predator species are noted for taking disadvantaged prey (e.g., Sargeant et al. 1973), most are capable of preying on healthy waterfowl (see references in Table 12-3).

Mink, large gulls, and jaegers are important predators of prefledged waterfowl. Talent et al. (1983) found that predation by mink was the major cause of mortality of prefledged Mallards they studied in North Dakota. Predation by large gulls on small goslings and on ducklings can be severe in certain situations (e.g., Dwernychuk and Boag 1972, Eisenhauer and Kirkpatrick 1977, Braun et al. 1980). Vermeer (1970a, p.38) described a situation in Alberta in which Gadwalls and Lesser Scaup nesting on islands among California and Ring-billed Gulls experienced high nest success (about 90%) but probably fledged few young because "as soon as a hen entered the water with her ducklings the gulls would pursue them, devouring the entire brood usually within ten minutes." Anderson (1965) suggested that broods hatched on gull-nesting islands in California may have escaped predation by gulls by departing the islands at night when the gulls were inactive.

D. Contaminants

Arctic-nesting waterfowl have relatively little exposure to contaminants during the breeding season (e.g., Anderson et al. 1984). In other areas, especially agricultural regions, breeding waterfowl are exposed to a variety of potentially harmful substances (e.g., White and Stickel 1975, Wobeser 1981, Grue et al. 1986, Sheehan et al. 1987). Blus et al. (1979) concluded that a local population of Canada Geese in Washington was in danger of extirpation due to ingestion of cereal grain treated with heptachlor. The treated grain caused deaths of adults and lowered reproductive success. Use of zincphosphide-treated oats to control voles killed thousands of migrating geese (several species) and an undetermined proportion of local breeding Canada Geese in the Klamath Basin of California and Oregon in March 1958 (Ashworth 1979).

Most commonly, concentrations of contaminants in waterfowl are below levels likely to cause direct mortality or adversely affect reproduction (e.g., Longcore et al. 1983, Anderson et al. 1984, Ohlendorf and Miller 1984, Mora et al. 1987). Breeding waterfowl sometimes make extensive use of sewage lagoons (Swanson 1977, Piest and Sowls 1985) or other sites that are likely to contain a variety of contaminants, but little mortality has been reported for these sites. Lead poisoning causes substantial mortality among migrating and wintering waterfowl in some areas, but this contaminant has not been identified as a cause of significant mortality among breeding waterfowl (see review by Sanderson and Bellrose 1986).

Although the direct effects of contaminants on survival of breeding adults do not appear to be substantial, their secondary effects may be greater. Hunter et al. (1984) demonstrated that aerial spraying of carbaryl (used to control spruce budworms) significantly reduced invertebrate biomass in ponds and decreased growth rates of Mallard and North American Black Duck ducklings. Brown and Hunter (1984-85) suggested that insecticides used to control mosquitoes might reduce invertebrate biomass available to breeding female dabbling ducks and their young, thereby affecting egg-laying potential, hatchability, and survival of young. Sublethal effects of contamination may render waterfowl more vulnerable to other mortality factors such as disease and predation (Wobeser 1981, Grue et al. 1986). Recently, acid precipitation has been suggested as a possible contributing factor to declining numbers of North American Black Ducks because of the adverse effects of acidity on invertebrate populations needed as food by egg-laying females and ducklings (Haines and Hunter 1981, Haramis and Chu 1986). McAuley and Longcore (1988) found that daily survival rates of Ring-necked Duck ducklings were lower on highly acidic wetlands than on less acidic wetlands. The highly acidic wetlands contained less invertebrate duck food than the less acidic wetlands.

Mortality of eggs from contamination has received considerable attention. Metabolites of DDT (principally DDE), which was widely used from the late 1940s through 1972, caused eggshell thinning and reduced reproductive success of several bird species (e.g., Ratcliffe 1967, 1970; Hickey and Anderson 1968; Anderson and Hickey 1972; Cooke 1973). Although species most affected were raptors and piscivorous seabirds, some waterfowl were also adversely affected (Heath 1969, Faber and Hickey 1973). Laboratory studies confirmed that eggshell thinning in Mallards (Heath et al. 1969, Lehner and Egbert 1969, Davison and Sell 1974, Greenburg et al. 1979) and North American Black Ducks (Longcore et al. 1971, Longcore and Samson 1973, White and Stickel 1975, Wobeser 1981, Longcore and Stendell 1982) could be induced by chlorinated hydrocarbons.

White and Cromartie (1977) found generally low levels of organochlorines and no significant thinning of shells in eggs of the generally insectivorous Hooded Merganser but potentially dangerous levels of DDE and PCBs and significant shell thinning in eggs of the piscivorous Red-breasted and Common Mergansers. By 1978, 6 years after legal use of DDT in the United States was suspended, the thickness of North American Black Duck eggshells, which had thinned during the period of wide spread use of DDT, had returned to the pre-DDT period mean (Haseltine et al. 1980).

Although DDE is still one of the most persistent and widely distributed pesticide residues found in waterfowl, most North American waterfowl populations do not appear to be seriously threatened by use of this chemical. (DDT may still be used in some local areas in the United States and may be widely used in some important waterfowl winter areas in Latin America [e.g., Mora et al. 1987].)

There was major concern about the impact of mercury on waterfowl during the 1960s and early 1970s (e.g., Krapu et al. 1973, White and Stickel 1975). In addition to being industrial pollutants (Fimreite 1974, White and Stickel 1975, Stendell et al. 1976), mercury compounds were widely used in fungicides for seed treatment until the 1970s (Peterson et al. 1976, Sherbin 1979). Relatively high levels of mercury were found in tissues and eggs of waterfowl at numerous locations, especially in species that consumed a high proportion of animal matter (Vermeer and Armstrong 1972, Vermeer et al. 1973, Fimreite 1974, Stendell et al. 1976). Treated seeds were believed to be a major source of this contaminant for field-feeding waterfowl in the prairie-parkland region (Vermeer and Armstrong 1972, Krapu et al. 1973). Laboratory studies showed that high levels of mercury could lower reproductive success of Mallards and North American Black Ducks (Heinz 1975, White and Stickel 1975). As with DDT, the effects of mercury on North American waterfowl populations were never determined, but steps taken to reduce levels of this contaminant in the environment appear to have greatly reduced its potential effects on waterfowl populations (e.g., Stendell et al. 1976).

Hatchability of eggs in active nests at protected sites is generally high, indicating that the overall effects of contaminants on waterfowl populations in terms of reduced hatchability of eggs are low. However, local problems exist. For example, selenium from agricultural drain waters has caused deformities and deaths of embryos and young of dabbling ducks and other aquatic bird species nesting at Kesterson National Wildlife Refuge in California (Ohlendorf et al. 1986).

Oil spills have caused large losses of wintering and migrant waterfowl (White and Stickel 1975) but relatively few losses of breeding waterfowl. The potential effects of oil spills on reproductive success of waterfowl have received attention as a result of increased offshore oil exploration and development and associated transport of oil from, through, or into areas used by breeding waterfowl. Szaro et al. (1978), Albers (1980), and others (see Szaro et al. 1981) demonstrated that hatchability of Mallard eggs coated with small quantities of petroleum was markedly reduced but that survivorship of young hatched from coated eggs was not affected. Laboratory studies revealed that Mallard duckling growth and survival were adversely affected by ingestion of small amounts of crude or fuel oil (Szaro et al. 1981).

A potentially serious effect of contaminants on waterfowl is on survival of prefledged young in areas where there is heavy use of agricultural pesticides (Sheehan et al. 1987, Grue et al. 1988). Laboratory studies have demonstrated that contaminants can affect duckling growth and vigor (Heinz 1975, Szaro et al. 1981). Field experiments have demonstrated that contamination resulting from applications of some agricultural pesticides (e.g., ethyl-parathion) may kill ducklings directly (Grue et al. 1988). However, the greatest threat of pesticides to duckling survival likely relates to abundance of invertebrates in wetlands (Grue et al. 1986, Sheehan et al. 1987, Grue et al. 1988). Sheehan et al. (1987) identified the synthetic pyrethroids cypermethrin, deltamethrin, and permethrin and the organophosphates azinphosmethyl and chlorpyrifos as being particularly harmful to wetland invertebrate populations. Stresses, especially on newly hatched young, from exposure to contaminants and from contaminant-caused food shortages would likely place young at greater risk of mortality from other agents such as inclement weather, predation, and disease (Wobeser 1981, Grue et al. 1986).

E. Diseases

Bellrose (1980, p.68) concluded that most nonhunting losses of adult waterfowl were attributable directly or indirectly to diseases (including lead poisoning). This conclusion was based largely on early evidence (before 1970) and the supposition that relatively little mortality occurred during the breeding season.

North American waterfowl are affected by a host of diseases that may affect breeding populations (see review by Wobeser 1981). Friend (1981) identified three diseases as having the capability to inflict heavy losses on North American waterfowl: avian botulism, avian cholera, and duck viral entiritus (DVE). Although these diseases have caused severe mortality among concentrations of molting, migrant, and wintering waterfowl, they have not been strongly implicated in mortality among breeding waterfowl. Relatively few outbreaks of botulism have been reported during the breeding season (Wobeser 1981).

A few outbreaks of avian cholera have been reported among colonies of nesting Common Eiders (Gershman et al. 1964, Reed and Cousineau 1967, Korschgen et al. 1978) and among colonies of Snow Geese (Wobeser 1981). Reed and Cousineau (1967) reported that during 2 consecutive years 17% and 25% of nesting female Common Eiders died from avian cholera on an island in the St. Lawrence Estuary, Quebec. Avian cholera may linger in breeding populations, causing little mortality, but may suddenly result in an epizootic (Korschgen et al. 1978) that may be triggered by stressors such as adverse weather or overcrowding (Wobeser 1981, Brand 1984).

DVE was first diagnosed in waterfowl in North America in 1967, but the only major epizootic in wild waterfowl occurred during winter (Wobeser 1981). The disease results in carrier birds, some of which can shed the virus for up to 4 years and can pass the virus through eggs to young (see review by Wobeser 1981). Hence, this disease has potential for epizootic outbreaks during the breeding season.

The lack of documentation of substantial recurring mortality from diseases among colonial-nesting waterfowl and among waterfowl nesting in sites protected from predation indicates that diseases, by themselves, are not widespread major mortality factors affecting adult waterfowl or their eggs during the breeding season. The importance of diseases in the survivorship of prefledged waterfowl is unknown.

Parasites have occasionally been identified as causes of mortality among North American waterfowl, especially prefledged young. Leech parasitism is widespread among adult and juvenile waterfowl, but there have been relatively few reports of leech-caused deaths (Bartonek and Trauger 1975, Trauger and Bartonek 1977). However, the behavior of affected birds indicated they would have been at increased risk to predation. Munro (1963) indicated that infection by the nematode Echinuria may be a serious mortality factor for ducklings in some areas. The blood parasite Leucocytozoon has been reported in breeding waterfowl in widely scattered areas but has not been identified as causing major mortality among ducks (Wright 1954, Jahn and Hunt 1964). However, it was considered a major cause of mortality of goslings in an introduced flock of Canada Geese on Seney National Wildlife Refuge, Michigan (Sherwood 1968); all goslings appeared to have been infected with the parasite each year but, for undetermined reasons, the mortality rates were cyclic, with severe losses occurring at about 4-year intervals (Herman et al. 1975). Ball (1973) reported a case of aspergillosis in a Mallard duckling in Minnesota, and Wobeser et al. (1981) reported three instances of fatal myiasis among recently hatched ducklings on a study area in Saskatchewan.

F. Subsistence Hunting

Historically, subsistence hunting during spring and summer was a major factor in the decline, and even extirpation, of numerous local waterfowl populations. Waterfowl groups most adversely affected were large bodied, usually colonial or semicolonial nesters (especially swans, geese, and Common Eiders), and waterfowl nesting on islands (Cott 1953/1954, Ogilvie 1978). Cott (1953/1954) listed 43 species of Anseriformes that had been subjected to heavy exploitation of their eggs. He concluded that egg gathering was likely a major factor in marked population declines and restrictions of ranges of the Hawaiian Goose, Brant, and Common Eider and in decimation of populations of the Whooper Swan, Tundra Swan, Black Swan, White-fronted Goose, Pink-footed Goose, and Yellow-billed Duck.

In North America, it seems likely that even before settlement by Europeans, subsistence hunting during spring and summer limited the size of some local waterfowl populations, e.g., Canada Geese along the Columbia River, Washington (Hanson and Eberhardt 1971). Thereafter, the settlement of North America by Europeans led to extirpation of several waterfowl populations, especially of swans and geese (e.g., Banko 1960, Hanson 1965, Hanson and Eberhardt 1971).

The egg-gathering activities of people on the North Atlantic coast in the 1800s and early 1900s had decimating effects on Common Eiders and some other bird populations and serve as vivid reminders of how easy it is to destroy such vulnerable populations (Knight 1895, Beetz 1916, Gross 1944, Cott 1953/1954). Cott (1953/ 1954) cited J. J. Audubon as recording in 1833 that just four men took and sold nearly 40,000 eggs of gulls, guillemots, and ducks near Halifax, Nova Scotia. Such activities possibly contributed to extinction of the Labrador Duck (Bellrose 1980, p. 43). Restrictions on harvests of waterfowl during the breeding season and establishment of sanctuaries gradually eliminated most of the severe overharvests of waterfowl by subsistence hunters and resulted in at least partial recovery of many decimated waterfowl populations (e.g., Gross 1944, Cott 1953/1954).

In the arctic and subarctic regions of North America, subsistence hunting of waterfowl during the breeding season continued after enactment of the 1916 Migratory Bird Treaty, which prohibited such activities (Cott 1953/1954). The consensus was that subsistence hunting by native Eskimos and Indians was necessary and of little consequence in relation to the overall status of waterfowl populations or the magnitude of harvests during fall and winter (e.g., Manning 1942; Barry 1964, 1968; Dzubin et al. 1964). However, some observers expressed concern about the effects of subsistence hunting on certain local goose populations (see review by King and Derksen 1986). For example, Spencer et al. (1951) thought that subsistence hunting around villages on the Yukon-Kuskokwim Delta, Alaska, was depressing those local goose populations. Klein (1966) estimated that subsistence hunters harvested up to 15% of some goose populations on the Yukon-Kuskokwim Delta each year in addition to their harvest of thousands of eggs. Eisenhauer (1977) observed one party of subsistence hunters in that area collect 51 adult geese and 657 eggs in a 10-hour period. He also reported that subsistence hunters took at least 7.7% of 207 newly banded, flightless Brant goslings; within 10 days of banding. For certain goose stocks in the vicinity of native settlements in Alaska, subsistence hunting during the breeding season represented a major mortality factor (Raveling 1984).

Hanson et al. (1956) suggested that the hunting and other activities by Eskimos in the Queen Maude Gulf region of Canada contributed to abandonment by Ross' Geese of their coastal nesting lakes. At present, subsistence hunting of most goose stocks in the arctic and subarctic regions of Canada does not appear to be excessive in relation to sizes of the respective populations of geese in those areas (Boyd 1977, Cooch 1986).

G. Miscellaneous