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Technical Thematic Report No. 8. - Trends in breeding waterfowl in Canada

Results by ecozone

 

Atlantic Maritime Ecozone+

Both the CWS and USFWS monitor waterfowl populations in the Atlantic Maritime Ecozone+ and results from an analysis which integrated observations from both surveys were used for this report. The selection of species was based on a combination of the historical and/or current importance of the species to this ecozone+ and data availability.

Trends indicate either stable or increasing populations (Table 7 and Figure 3). The American Black Duck, the most abundance duck species in the ecozone+, has been the focus of special conservation effort because the population in the United States declined by almost 50% between 1955 and 1985 (Lepage and Bordage, 2003). This prompted the creation of the Black Duck Joint Venture under the NAWMP to improve knowledge of Black Ducks and guide conservation and management decisions. Logging, hydroelectric development, transmission line construction, agriculture, urbanization, and other industrial developments threaten American Black Duck breeding and staging habitats (Lepage and Bordage, 2003). A more recent threat is competition for habitat, particularly in agricultural areas, with the Mallard (Petrie et al., 2000), which has been expanding its breeding range and increasing in abundance throughout eastern North America (Lepage and Bordage, 2003). Habitat availability and quality may not be limiting for dabbling ducks. Mallards and Black Ducks nesting in a heavily farmed area in midwestern New Brunswick were found to have breeding vital rates (such as nest success, hen success, and duckling survival) above the level thought necessary to maintain population size (Petrie et al., 2000). The recent increases and stabilization of the American Black Duck population in the Atlantic Maritime may be due to changes in management practices (such as, increased hunting restrictions in both Canada and the United States) (Longcore et al., 2000).

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Table 7. Abundance trends for selected breeding waterfowl species in the Atlantic Maritime Ecozone+.
SpeciesNesting habitatTrend (%/yr) P Annual Index (in 1000s)

1990s
Annual Index (in 1000s)

2000s
Annual Index (in 1000s)

% change
MallardGround30.084*2.34.698.1
American Black DuckGround2.214 57.763.710.5
Green-winged TealGround5.892n8.411.738
Ring-necked DuckOverwater6.479*21.232.352.2
Canada Goose 22.502*1.13.6244.3

P is the statistical significance, * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant
Source: data from USFWS Airplane Transect Survey and CWS Boreal Helicopter Plot Survey

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Figure 3. Population trends for Canada Goose, selected diving ducks (Ring-necked Duck), and dabbling ducks (Green-winged Teal, American Black Duck, and Mallard) in the Atlantic Maritime Ecozone+, 1993-2006.
Graph

Source: data from USFWS Airplane Transect Survey and CWS Boreal Helicopter Plot Survey

Long Description for Figure 3

This line graph shows population trends for Canada Goose, selected diving ducks (Ring-necked Duck), and dabbling ducks (Green-winged Teal, American Black Duck, and Mallard) in the Atlantic Maritime Ecozone+, from 1993 to 2006. American Black Duck populations increased from about 40,000 in 1993, peaking to almost 80,000 in 2000. Ring-necked Duck has shown a steady increase from around 17,000 to 36,000 by 2005 with a sharp increase to roughly 58,000 in 2006. Green-winged Teal populations increased steadily, from about 5,000 to 11,000. Mallard and Canada Goose populations show similar growth, increasing from roughly 300 to 5,000.

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Green-winged Teal and Ring-neck Duck populations also increased since the 1990s although the reasons remain unknown. Increases in the Canada Goose population are consistent with other regions within the goose's temperate breeding range (Dickson, 2000).

Although not well captured by the monitoring surveys used in this analysis, Barrow's Goldeneye (Bucephala islandica) and Harlequin Ducks have been assessed as Species of Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC, 2006). The Barrow's Goldeneye winters along the coast of this ecozone+ (Eadie et al., 2000), while the Harlequin Duck breeds along the north shore of the Gulf of St. Lawrence, the Gaspé Peninsula, and northern New Brunswick, and many winter on the east and south coast of New Brunswick. Oil spills and sediment contamination are threats to survival of these species in their wintering habitat (COSEWIC, 2006). In addition, some previously fast-flowing streams where Harlequin Ducks nest have been altered by hydro and mining projects (COSEWIC, 2006).

The Atlantic Maritime has many coastal areas where large numbers of waterfowl traditionally congregate during the spring and fall migration (U.S. Fish and Wildlife Service, 2009), and many waterfowl also winter in this ecozone+. Recent milder winters with longer ice free periods have resulted in an increase in wintering populations and a potential increase in the residency time of waterfowl during migration (EHJV, 2007b).

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Mixedwood Plains Ecozone+

The CWS monitors waterfowl populations in the Mixedwood Plains Ecozone+ (Dennis, 1974). Relative to other ecozones+, this is a moderately important region to waterfowl because it provides habitat during breeding, staging, and wintering. The selection of species was based on a combination of the historical and current importance of the species and data availability.

Results show different population trajectories among species (Table 8 and Figure 4). Between the 1990s and 2000s, Blue-winged Teal and American Black Duck declined considerably; Mallard remained stable; and Canada Goose increased substantially.

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Table 8. Abundance trends for selected breeding waterfowl species in the Mixedwood Plains Ecozone+.
SpeciesNesting habitatTrend (%/yr)Average Index
(in 1000s)

1990s
Average Index
(in 1000s)

2000s
Average Index
(in 1000s)

% change
Blue-winged TealGroundN/A6.23.8-37.8
American Black DuckGroundN/A11.45.9-48.2
MallardGroundN/A92.695.02.5
Canada GooseGroundN/A30.757.085.7

Source: data from the Southern Ontario Waterfowl Ground Survey

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Figure 4. Population trends for selected breeding dabbling ducks (Mallard, American Black Duck, and Blue-winged Teal) and Canada Goose in the Mixedwood Plains Ecozone+, 1992-2006.
Graph

Source: data from the Southern Ontario Waterfowl Ground Survey

Long Description for Figure 4

This line graph shows population trends for selected breeding dabbling ducks (Mallard, American Black Duck, and Blue-winged Teal) and Canada Goose in the Mixedwood Plains Ecozone+ from 1992 to 2006. The Mallard population remained stable fluctuating around 90,000. Canada Goose populations increased steadily from around 23,000 to 67,000. Both American Black Duck and Blue Winged Teal populations declined, from roughly 16,000 to 7,000 and almost 9,000 to 1,000, respectively.

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The Blue-winged Teal has significantly declined to the point where it is rarely detected during surveys. This decline is likely the result of fewer wetlands on the landscape. Shifts in agricultural practices (for example, conversion of pasture land to cropland and tile drainage or natural succession of marginal farmland to forest) has resulted in a decrease in seasonal wetlands and, to a lesser extent, semi-permanent wetlands (EHJV, 2007c).

The Mallard population remained stable from the 1990s to 2000s. However, prior to the 1950s, the Mallard was likely not found in Ontario and it has become the most abundant and widely distributed duck species in the province (Zimmerling, 2007).

Once one of the most abundant breeding ducks in the Mixedwood Plains Ecozone+, the American Black Duck has declined since the 1960s (Ross, 2007). This led to its designation as a species of concern under NAWMP. Reasons for the decline are not clear but potential causes include loss of habitat and displacement as a result of interspecific competition and introgression with the Mallard which, as noted above, dramatically increased in numbers (EHJV, 2007c).

The temperate breeding Canada Goose population has increased substantially in the ecozone+ and similarly throughout the rest of its breeding range (Canadian Wildlife Service Waterfowl Committee, 2008). The species easily adapts to a variety of habitats, including farmland and urban areas. This has allowed them to take advantage of the conversion of native habitat to cultivated land and urban areas, benefitting from increased cereal grain, planted forage, and turf grass food sources (Mowbray et al., 2002).

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Newfoundland Boreal Ecozone+

Waterfowl populations in the Newfoundland Boreal have been monitored jointly by CWS and USFWS since 1990. Compared to other ecozones+, the Newfoundland Boreal is moderately important for breeding waterfowl. Inland and coastal wetlands in this ecozone+ are used by waterfowl for breeding and during the spring and fall migration (U.S. Fish and Wildlife Service, 2009). The Harlequin Duck (Histrionicus histrionicus), assessed as a Species of Special Concern by Committee on the Status of Endangered Wildlife in Canada (COSEWIC, 2006), is known to moult along the Newfoundland coast (Gilliland et al., 2002) and American Black Duck (Anas rubripes), King Eider (Somateria spectabilis), Long-tailed Duck (Clangula hyemalis), and especially, Common Eider (Somateria mollissima borealis/dresseri) are known to regularly over-winter in the open waters surrounding Newfoundland (Bellrose, 1980).

Population trends of selected species reveal that waterfowl populations in this ecozone+ were generally stable or increasing between the 1990s and 2000s (Table 9 and Figure 5). Newfoundland lacks several nest predators, including the striped skunk (Mephotos mephitis Schreger) and raccoon (Procyon lotor), that are common in other regions (Thompson et al., 2008). Inland nesting habitat in particular does not appear to be limiting except for the cavity nesting Common Goldeneye (Bucephala clangula) (EHJV, 2007a). Reasons for the declining trend of Green-winged Teal (Anas carolinensis) remain unclear.

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Table 9. Abundance trends for selected breeding waterfowl species in the Newfoundland Boreal.
SpeciesNesting habitatTrend (%/yr) P Annual Index
(in 1000s)

1990s
Annual Index
(in 1000s)

2000s
Annual Index
(in 1000s)

% change
American Black DuckGround1.988n15.919.421.9
Green-winged TealGround0.805 4.13.6-11.6
Ring-necked DuckOverwater3.2*11.519.569.3
Common GoldeneyeCavity3.922 4.97.146.1
Canada Goose 3.532*11.513.113.9

P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant
Source: data from USFWS Airplane Transect Survey and the CWS Boreal Helicopter Plot Survey

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Figure 5. Population trends for selected diving ducks (Ring-necked Duck and goldeneye), dabbling ducks (Green-winged Teal and American Black Duck), and Canada Goose in the Newfoundland Boreal Ecozone+, 1990-2006.
Graph

Source: data from USFWS Airplane Transect Survey and CWS Boreal Helicopter Plot Survey

Long Description for Figure 5

This line graph shows population trends for selected diving ducks (Ring-necked Duck and goldeneye), dabbling ducks (Green-winged Teal and American Black Duck), and Canada Goose in the Newfoundland Boreal Ecozone+ from 1990 to 2006. American Black Duck populations fluctuated, but generally increased in this period, from around 15,000 to 20,000 with a sharp peak up to almost 35,000 in 2000. Ring-necked Duck populations also increased from around 15,000 to 20,000, with the exception of two dips from 1997 to 1999 and in 2003. Canada Goose populations increased from over 7,000 to almost 13,000.

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Boreal Shield Ecozone+

Although waterfowl densities are relatively low in the Boreal Shield Ecozone+, it is of considerable importance to waterfowl due to its large area. Both breeding and staging waterfowl from the Atlantic, Mississippi, and Central Migratory Flyways occur in this ecozone+ (U.S. Fish and Wildlife Service, 2009). There are a variety of data sources from which breeding waterfowl population trends can be generated in this area. In order to maximize data use, this ecozone+ was divided into eastern and western sections, using a division of approximately 86°E. The western area is covered by the CWS/USFWS Waterfowl Breeding Population and Habitat Survey and the eastern area is covered by the USFWS Airplane Transect Survey and the CWS Boreal Helicopter Plot Survey.

In the western portion of the ecozone+, population trends of American Wigeon, and scaup (combined Lesser Scaup (Aythya affinis) and Greater Scaup (A. marila)) indicate declines over the survey period, particularly over the last decade (Table 10 and Figure 6). These declining trends were also found in neighbouring ecozones+ (Boreal Plains, Taiga Plains, Taiga Shield, and Prairies) suggesting common factors that operate within or beyond the breeding areas. Although little research has been carried out on American Wigeon, some research has been testing various hypotheses for the scaup decline (Austin et al., 2000).

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Table 10. Abundance trends for selected breeding waterfowl species in the western portion of the Boreal Shield Ecozone+.
SpeciesNesting
habitat
Trend
(%/yr)
PAnnual Index
(in 1000s)

1970s
Annual Index
(in 1000s)

1980s
Annual Index
(in 1000s)

1990s
Annual Index
(in 1000s)

2000s
Annual Index
(in 1000s)

% change
Ring-necked
Duck
Overwater3.463*153.5199.9337.7433.9182.7
BuffleheadCavity0.591 6455.773.67923.5
Goldeneye
(Common and Barrow's)
Cavity1.545*170174.6268.7272.360.2
American WigeonGround-2.043*152.1127.8115.679.6-47.6
Scaup
(Lesser and Greater)
Ground-1.919*236.7202.8200.8133.7-43.5
Scoter
(White-winged and Surf)
Ground-0.998 50.756.647.144.1-13.1
MallardGround-0.452 635.8599.8649.4555.3-12.7
Green-winged TealGround1.794*101101.8152.2140.639.2
Canada GooseGround3.655*68.6100130.7165.1140.6
Pond -1.121*84.657.560.252.3-38.2

P is the statistical significance: * indicates P<0.05; no value indicates not significant
Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

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Figure 6. Population trends for breeding American Wigeon, scaup, scoter, Mallard, and Green-winged Teal in the western Boreal Shield Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 6

This line graph shows population trends for breeding American Wigeon, scaup, scoter, Mallard, and Green-winged Teal in the western Boreal Shield Ecozone+ from 1970 to 2006. Mallard populations are stable in the long term despite considerable year-to-year variation between roughly 300,000 and 1,000,000. American Wigeon, scaup, scoter, and Green-winged Teal populations share a similar variable, yet stable pattern for this period.

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The population trends of scoters (combined White-winged (Melanitta fusca) and Surf (M. perspicillata), Buffleheads (Bucephala albeola), and Mallards have remained stable over the long term despite considerable year-to-year variation. This is a pattern common to waterfowl (Figure 6 and Figure 7).

Figure 7. Population trends for breeding Bufflehead, goldeneye, Ring-necked Duck, and Canada Goose in the western Boreal Shield Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 7

This line graph shows population trends for breeding Bufflehead, goldeneye, Ring-necked Duck, and Canada Goose in the western Boreal Shield Ecozone+ from 1970 to 2006. Goldeneye populations are stable for several years around 200,000 before they substantially increased for a seven year period starting in the mid-1990s. Ring-necked Duck populations are also generally stable around 200,000 with a substantial increase in the early 1990s. Canada Goose populations increased gradually from about 60,000 to 150,000. Bufflehead populations trends are generally stable around 70,000.

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Some species experienced an increase in population although the population trajectories differed among species and causes for these trends remain unclear. For example, the Green-winged Teal experienced a gradual increase with considerable annual variation, whereas the goldeneye (combined Common and Barrow's) population was stable for several years before it substantially increased for a seven year period starting in the mid-1990s. It has recently dropped back to its historical level, however. The cause of the increase of the Ring-necked Duck population across its breeding range remains unclear as it considerably overlaps with scaup and shares many life history traits (such as, wintering area, breeding area and season, and diet) (De Vink et al., 2008).

Canada Goose populations are showing increasing trends in both the eastern and western regions of the Boreal Shield Ecozone+ (Table 10 and Table 11). This is a similar trend to those seen in other ecozones+ that have temperate nesting breeding populations. Temperate nesting Canada Geese have likely benefited from the conversion of forest to cultivated land and urban areas, taking advantage of planted forage and turf grass as food sources (Mowbray et al., 2002).

Table 11. Abundance trends for selected breeding waterfowl species in the eastern portion of the Boreal Shield Ecozone+.
SpeciesNesting
habitat
Trend
(%/yr)
PAnnual Index
(in 1000s)

1990s
Annual Index
(in 1000s)

2000s
Annual Index
(in 1000s)

% change
Ring-necked DuckOverwater2.395*95.7119.725
BuffleheadCavity-2.169 9.69-6.2
Goldeneye (Common and Barrow's)Cavity2.155 86.7107.123.5
Green-winged TealGround-1.654 3432.2-5.1
American Black DuckGround1.315*141.6162.414.7
MallardGround3.896*64.488.236.8
Canada Goose 6.746*27.147.475.4

P is the statistical significance: * indicates P<0.05; no value indicates not significant
Source: data from USFWS Airplane Transect Survey, CWS Boreal Helicopter Plot Survey, and Southern Ontario Waterfowl Ground Survey

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Some of the trends in the eastern Boreal Shield are similar to those observed in the west (Figure 8 and Figure 9). Ring-necked Ducks increased in the east, while other species remained stable (Bufflehead, Green-winged Teal, Mallard). The population trend for goldeneyes (combined Common and Barrow's) slightly increased, although not significantly. The eastern population of Barrow's Goldeneye was assessed by COSEWIC as Special Concern in November 2000 (COSEWIC, 2006). These cavity-nesting ducks are found breeding in eastern Québec and wintering along the Gulf of St. Lawrence and the St. Lawrence Estuary (Eadie et al., 2000). Potential threats to this species includes accumulation of heavy metals in prey items, recreational development on breeding lakes, loss of nesting habitat due to timber harvest (especially large trees for nesting), and fish introductions (Eadie et al., 2000). Timber harvest can destroy nests, reduce the number of potential nest sites, expose young to predation, and increase disturbance by making lakes more accessible (COSEWIC, 2006). Some lakes that were originally fishless have been stocked with brook trout in some areas, and there are indications that the fish presence could reduce the quality of lakes for Barrow's Goldeneye (COSEWIC, 2006).

Figure 8. Population trends for selected breeding dabbling ducks (American Black Duck, Green-winged Teal, and Mallard) in the eastern Boreal Shield Ecozone+, 1990-2006.
Graph

Source: data from USFWS Airplane Transect Survey, CWS Boreal Helicopter Plot Survey, and the Southern Ontario Waterfowl Ground Survey

Long Description for Figure 8

This line graph shows population trends for selected breeding dabbling ducks (American Black Duck, Green-winged Teal, and Mallard) in the eastern Boreal Shield Ecozone+ from 1990 to 2006. American Black Duck populations decrease up until 1994 when they increase sharply and generally stabilize around 175,000. Mallard populations gradually increased to about 80,000 from 40,000. Green-winged Teal populations are essentially stable around 30,000.

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Figure 9. Population trends for Canada Goose and selected diving ducks (Bufflehead, goldeneye (Common and Barrow's), and Ring-necked Duck) in the eastern Boreal Shield Ecozone+, 1990-2006.
Graph

Source: data from USFWS Airplane Transect Survey, CWS Boreal Helicopter Plot Survey, and the Southern Ontario Waterfowl Ground Survey

Long Description for Figure 9

This line graph shows population trends for Canada Goose and selected diving ducks (Bufflehead, goldeneye (Common and Barrow's), and Ring-necked Duck) in the eastern Boreal Shield Ecozone+ from 1990 to 2006. Both Goldeneye and Ring-necked Duck populations increase over this period, from roughly 68,000 and 86,000 to 88,000 and 117,000 respectively. Canada Goose increased steadily from about 20,000 to almost 48,000 during this period. Bufflehead populations decreased steadily from 21,000 in 1990, dropping below 2,000 in 1993, and fluctuating around 8,000 through the remainder of the period.

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The Mallard population has increased in the eastern Boreal Shield (Figure 8), a trend common to other eastern ecozones+ and consistent with its range expansion in the east. The American Black Duck has been the focus of special conservation effort because the population in the United States decreased by almost 50% between 1955 and 1985 (Lepage and Bordage, 2003). This prompted the creation of the Black Duck Joint Venture under NAWMP to improve knowledge and guide conservation and management decisions. Logging, hydroelectric development, transmission line construction, agriculture, urbanization, and industrial development may threaten American Black Duck breeding and staging habitats in Québec (Lepage and Bordage, 2003). In addition, in southern Québec, the American Black Duck has recently had to compete for habitat with the Mallard which has been expanding its breeding range in this region (Lepage and Bordage, 2003). The recent increases in the American Black Duck population in the eastern Boreal Shield may be due to changes in management practices (such as increased hunting restrictions in both Canada and the United States) (Longcore et al., 2000).

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Taiga Shield Ecozone+

There are a variety of data sources from which breeding waterfowl population trends can be generated in the Taiga Shield Ecozone+. In order to maximize data use, this ecozone+ was divided into eastern and western portions, with Hudson Bay being the natural divider. The best data set on waterfowl species distribution, composition, and abundance in the eastern Taiga Shield comes from the joint CWS/USFWS Waterfowl Breeding Population and Habitat Surveys that were established in 1990. The western area is best covered by surveys initiated in 1955 by the CWS/USFWS although this survey only covers the area west of longitude 110oE, adjacent to the Taiga Plains Ecozone+. The selection of species is based on a combination of the historical and current importance of the species, and data availability.

Scaup (combined Lesser and Greater), American Wigeon, and scoter (combined White-winged and Surf) populations showed declining trends from the 1970s to 2000s (Table 12 and Figure 10). These declining trends were also found in neighbouring ecozones+ (Boreal Plains, Taiga Plains, Boreal Shield, and Prairie) suggesting common factors that operate either within or beyond the breeding areas. Although little research has been carried out on the American Wigeon, research has been testing various hypotheses for the scoter and, in particular, the scaup decline (Austin et al., 2000). Austin et al. (2000) suggested that contaminants, lower female survival, and reduced recruitment due to changes in food resources or breeding ground habitats were possible factors contributing to the decline in continental scaup populations. DeVink et al. (2008) found no support for a relationship between declines in Lesser Scaup and White-winged Scoter populations and selenium contamination. Specifically, they found spring selenium levels were low in Ring-necked Ducks and Lesser Scaup, and elevated levels detected in White-winged Scoters did not appear to be detrimental to female body condition or breeding propensity. Estimated female survival rates during the breeding season are similar throughout the Lesser Scaup breeding range (Koons and Rotella, 2003; Rotella et al., 2003; Brook and Clark, 2005). Similarly, body condition of Lesser Scaup breeding near Yellowknife, Northwest Territories, are relatively similar to that of Ring-necked Duck and to historical levels for Lesser Scaup. This provides evidence against decreases in spring female body condition as the primary cause for decreasing population trends in this species (De Vink et al., 2008), but see Anteau and Afton (2009). Lesser Scaup, White-winged Scoter, and American Wigeon are relatively late nesters (Brown and Fredrickson, 1997; Austin et al., 1998; Mowbray, 1999). De Vink et al. (2008) suggest that if there is a dependence on photoperiod as a breeding cue then a possible mismatch between timing of nesting (and therefore peak hen and duckling food requirements) and food availability may be occurring -- the availability of their invertebrate food source may be shifting with changing temperatures resulting in decreased hen and duckling survival. However, since very few studies have been conducted in the eastern Taiga Shield the reasons for these declining waterfowl population trends are not well understood.

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Table 12. Abundance trends for selected breeding waterfowl species in the western portion of the Taiga Shield Ecozone+.
SpeciesNesting habitatTrend (%/yr)PAnnual Index
(in 1000s)

1970s
Annual Index
(in 1000s)

1980s
Annual Index
(in 1000s)

1990s
Annual Index
(in 1000s)

2000s
Annual Index
(in 1000s)

% change
BuffleheadCavity-0.367 63.980.755.862.6-2
Scaup (Lesser and Greater)Ground-3.667*859.5604.6352.1318.9-62.9
American WigeonGround-3.024*127126.777.858.1-54.3
Scoter (White-winged and Surf)Ground-2.213*206.4162.988.5122.7-40.5

P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant
Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

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Figure 10. Population trends for breeding Bufflehead, scaup, American Wigeon, and scoter in the western Taiga Shield Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 10

This line graph shows population trends for breeding Bufflehead, scaup, American Wigeon, and scoter in the western Taiga Shield Ecozone+ from 1970-2006. Scaup populations fluctuate during the period, peaking sharply in 1972 over 14,000,000 but the trend is a steady decrease to around 200,000. Scoter and American Wigeon populations fluctuate around 150,000 and 100,000 respectively with a decreasing trend. Bufflehead populations are generally stable ranging from roughly 30,000 to 133,000 during the period.

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Within the eastern Taiga Shield, population monitoring has been carried out since the early 1990s by the USFWS. These surveys indicate that, although there were considerable year-to-year variations, the long-term trend is stable population levels for all species reported (Table 13 and Figure 11). As noted in the COSEWIC report on Harlequin Ducks (Environment Canada, 2007), hydro and mining projects and forestry activities could be adversely impacting the waterfowl breeding in this area. Hydro and mining project can alter water dynamics over large areas, and forestry activity can increase stream siltation that may affect food availability for the ducks (Crowley and Patten, 1996).

Table 13. Abundance trends for selected breeding waterfowl species in the eastern portion of the Taiga Shield Ecozone+.
SpeciesNesting HabitatTrend
(%/yr)
PAnnual Index
(in 1000s)

1990s
Annual Index
(in 1000s)

2000s
Annual Index
(in 1000s)

% change
Ring-necked DuckOverwater2.797 1.21.32.7
Scaup (Lesser and Greater)Overwater1.295 2.22.2-3.1
American Black DuckGround-2.205 7.46.6-10.5
Green-winged TealGround6.081 2.64.572.6

P is the statistical significance: no value indicates not significant
Source: data from USFWS Airplane Transect Survey

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Figure 11. Population trends for breeding American Black Duck, Green-winged Teal, scaup, and Ring-necked Duck in the eastern Taiga Shield Ecozone+, 1990-2006.
Graph

Source: data from USFWS Airplane Transect Survey

Long Description for Figure 11

This line graph shows population trends for breeding American Black Duck, Green-winged Teal, scaup, and Ring-necked Duck populations in the eastern Taiga Shield Ecozone+ from 1990 to 2006. Although there were considerable year-to-year variations, the long-term trends are stable for all species. American Black Duck populations range between 12,000 and 2,000 with smaller variations after 1998. Green-winged Teal populations fluctuate between 0 and 7,300 during the period. Scaup populations are at their highest at the start of the period, around 9,000, then drop below 2,000 for most of the 1990s, and increase above 5,000 by the end of the period. Ring-necked duck populations fluctuate around 1,300 for the period.

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Taiga Plains Ecozone+

Waterfowl population composition and abundance within the Taiga Plains Ecozone+ is surveyed by the joint CWS/USFWS Waterfowl Breeding Population and Habitat Survey.    Long-tailed Duck, scoters (combined White-winged, Surf, and Black (M. nigra), scaup (combined Lesser and Greater), Northern Pintail, Mallard, and American Wigeon show declining population trends (Table 14, Figure 12, and Figure 13). These populations have overlapping breeding areas and most have different wintering areas (Bellrose, 1980) suggesting that reasons for their declines may be linked to this region. Anthropogenic disturbances such as exploration activities for oil and gas have increased recently and may have negative influences on some species (personal observation). Population growth rate for Lesser Scaup may be most sensitive to adult female survival during the breeding and non-breeding seasons and to a lesser extent to nesting success, duckling survival, and juvenile survival (Koons et al., 2006), suggesting that changes to breeding habitat may greatly influence population growth. Similarly, like other seaducks, scoter population growth rates are likely most sensitive to changes in adult survival (Goudie et al., 1994; Robertson and Savard, 2002; Koons et al., 2006).

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Table 14. Abundance trends for selected breeding waterfowl species in the Taiga Plains Ecozone+.
SpeciesNesting habitatTrend (%/yr)PAnnual Abundance Index
(in 1000s)

1970s
Annual Abundance Index
(in 1000s)

1980s
Annual Abundance Index
(in 1000s)

1990s
Annual Abundance Index
(in 1000s)

2000s
Annual Abundance Index
(in 1000s)

% change
BuffleheadCavity0.104 96.396.285.697.41.2
Long-tailed DuckGround-4.164*42.630.612.511.6-72.8
Scoter (White-winged, Surf, and Black)Ground-4.089*250.3233.186.487.9-64.9
Scaup (Lesser and Greater)Ground-3.273*951.8744.5427.6384.3-59.6
Northern PintailGround-2.722*94.569.337.644.7-52.7
MallardGround-2.155*232.9237.2168.8131.6-43.5
American WigeonGround-2.024*194.1185.5119.7121.7-37.3
Green-winged TealGround0.665 141.7249163.5201.442.2
Canada Goose 0.472 54.768.163.365.419.5

P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant
Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

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Figure 12. Population trends for breeding American Wigeon, Green-winged Teal, Mallard, and Northern Pintail in the Taiga Plains Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 12

This line graph shows population trends for breeding American Wigeon, Green-winged Teal, Mallard, and Northern Pintail in the Taiga Plains Ecozone+ from 1970 to 2006. American Wigeon and Mallard populations show declining trends, from roughly 147,000 and 225,000, to 76,000 and 46,000 respectively. Northern Pintail population trends also indicate declines, with larger fluctuations in the 1970s (between roughly 25,000 to 218,000) then remaining around 50,000 until the end of the period.

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Figure 13. Population trends for breeding Canada Goose, scaup, scoter, Long-tailed Duck, and Bufflehead in the Taiga Plains Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 13

This line graph shows population trends for breeding Canada Goose, scaup, scoter, Long-tailed Duck, and Bufflehead in the Taiga Plains Ecozone+ from 1970 to 2006. Scaup, scoter, and Long-tailed Duck populations show declining trends. The most clear decline is evident in scaup populations which peak at 1,960,000 in 1972 and steadily decline to 250,000 by the end of the period. Scoter and Long-tailed Duck populations decrease from about 250,000 and 35,000 to 75,000 and 4,000 respectively. Canada Goose and Bufflehead populations show little trend, fluctuating around 60,000 and 90,000 respectively.

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White-winged Scoter pair density and brood occurrence were found to be positively related to amphipod abundance, and broods occurred more frequently on clear wetlands, perhaps due to improved foraging efficiency (Haszard and Clark, 2007). The role of forest fires may be less important as no differences were detected in water chemistry, wetland productivity, or amphipod abundance between wetlands surrounded by recently burned versus unburned forest (Haszard and Clark, 2007). The reasons for the declines of these waterfowl populations are not well understood, as very few waterfowl studies have been conducted in the Taiga Plains. Climate change may play an important role, especially for late-nesting Long-tailed Ducks, scoters, and scaup (see discussions in De Vink et al., 2008; and Drever et al., 2012). As photoperiod is likely the main breeding cue for these species, mismatches in timing may be occurring between their relatively fixed late nesting dates (but see Anteau and Afton, 2009) and invertebrate phenology, which is driven by temperature and has likely changed recently due to climate warming (Corcoran et al., 2009). The mismatch hypothesis between breeding birds and changing food supply, although not yet tested in the taiga regions, has been demonstrated elsewhere (for example Thomas et al., 2001). The mismatch hypothesis however, is one of many that may explain declines in scaup populations (see review in Austin et al., 2000). Causes for the declines observed for Northern Pintail, Mallard, and American Wigeon remain unclear. These species fluctuate greatly between years, and some have declines in other regions as well. Trends for Canada Goose and Green-winged Teal populations have remained unchanged, although the latter has undergone high year-to-year fluctuations, which is typical of this species.

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Boreal Plains Ecozone+

The distribution, composition, and abundance of waterfowl in the Boreal Plains Ecozone+ are best covered by the joint CWS/USFWS Waterfowl Breeding Population and Habitat Survey. This ecozone+ is one of the most important regions for breeding waterfowl in North America (North American Waterfowl Management Plan, 2004). A wide variety of waterfowl are found with a diversity of habitat requirements and migratory strategies. Some winter on Canadian coasts, while the majority winter in the United States and Mexico (Bellrose, 1980). Similar to other regions, the Boreal Plains is experiencing an increase in the population of temperate nesting Canada Geese (310% increase) (Table 15). This is likely due to the species having benefited from the conversion of forest to other land cover types where they can take advantage of food sources (Mowbray et al., 2002).

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Table 15. Abundance trends for selected breeding waterfowl species in the Boreal Plains Ecozone+.
SpeciesNesting habitatTrend
(%/yr)
PAnnual Index
(in 1000s)

1970s
Annual Index
(in 1000s)

1980s
Annual Index
(in 1000s)

1990s
Annual Index
(in 1000s)

2000s
Annual Index
(in 1000s)

% change
Ring-necked DuckOverwater0.775*66.174.695.386.631
CanvasbackOverwater1.485*3138.548.64338.6
BuffleheadCavity0.241 46.537.252.945.3-2.7
Goldeneye (Common and Barrow's)Cavity1.997*42.346.756.476.380.2
Scaup (Lesser and Greater)Ground-3.522*276.4235.4174.892.2-66.6
American WigeonGround-2.891*133.1103.290.951.6-61.3
Northern PintailGround-3.524*42.532.518.718-57.7
MallardGround-2.161*404.6283.1286.9196.9-51.3
Blue-winged TealGround-2.603*185.7224.7123.391.6-50.7
Northern ShovelerGround0.026 44.849.948.943.1-3.9
Green-winged TealGround0.125 52.553.465.351.2-2.5
Canada Goose 4.637*12.637.537.451.6310.6

P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant
Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

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Several waterfowl species have experienced population declines in the Boreal Plains Ecozone+, including scaup (combined Lesser and Greater), American Wigeon, Northern Pintail, Mallard, and Blue-winged Teal (Table 15 and Figure 14). Broad-scale cumulative impacts from anthropogenic activities (such as, conversion to agriculture, forestry, mining, and oil and gas) have rapidly increased throughout the region and could explain in part the observed trends. For example, rapid deforestation within the Boreal Plains (Hobson et al., 2002) likely has negative implications for many waterfowl similar to those reported for other regions (Stephens et al., 2003; Emery et al., 2005; Koper and Schmiegelow, 2006; Drever et al., 2007). Recent research within the Boreal Plains has found that overall waterfowl abundance was lower in disturbed landscapes, and abundance was similar in burned and logged landscapes (Bidwell et al., 2008). Cavity nesting waterfowl were less abundant in burned landscapes and overwater nesters were less abundant in logged landscapes (Bidwell et al., 2008). Closer examination of such patterns of boreal waterfowls at the landscape scale suggests that although fire and logging both negatively impact waterfowl populations, these natural and anthropogenic influences seem to be affecting community dynamics differently (Bidwell et al., 2006). In addition to the cumulative impacts from industry in the region, climate change may also have an important role in the declining populations. For example, it is possible that the chronology of breeding birds, which is largely fixed (that is driven by photoperiod) has become out of synchrony with the birds' changing food supply (Corcoran et al., 2009) -- see discussions in De Vink et al. (2008) and Drever et al. (2012). This "mismatch hypothesis", although not yet tested in the boreal region, has been demonstrated elsewhere (Thomas et al., 2001). Despite the factors mentioned above, the processes causing the currently observed waterfowl population trends in the Boreal Plains Ecozone+ are poorly understood.

Figure 14. Population trends for scaup, American Wigeon, Northern Pintail, Mallard, Blue-winged Teal, Northern Shoveler, and Green-winged Teal in the Boreal Plains Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 14

This line graph shows population trends for scaup, American Wigeon, Northern Pintail, Mallard, Blue-winged Teal, Northern Shoveler, and Green-winged Teal in the Boreal Plains Ecozone+ from 1970 to 2006. With the exception of Northern Shoveler and Green-winged Teal populations, which remained relatively stable around 47,000 and 56,000 respectively, trends for these waterfowl species show an overall decline. Mallard, Scaup, and Blue-winged Teal populations varied greatly but declined from roughly 636,000 to 185,000, 253,000 to 96,000, and 237,000 to 81,000, respectively, for the period. American Wigeon populations declined from about 171,000 to 40,000 and Northern Pintail populations declined from about 109,000 to 12,000.

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Figure 15. Population trends for breeding Ring-necked Duck, Bufflehead, goldeneye (Common and Barrow's), and Canada Goose in the Boreal Plains Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 15

This line graph shows population trends for breeding Ring-necked Duck, Bufflehead, goldeneye (Common and Barrow's), and Canada Goose in the Boreal Plains Ecozone+ from 1970 to 2006. Population trends for all species fluctuate annually, and show little evidence of a general trend. The Ringed-neck duck populations show the greatest variance, particularly in 1993 when they spiked to 244,000. Goldeneye populations also vary widely from approximately 16,000 to 125,000. Canvasback, Bufflehead, and Canada Goose populations fluctuate around 40,000, 45,000, and 33,000 respectively.

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Prairies Ecozone+

The best dataset on waterfowl species distribution, abundance, and community composition for the Prairies Ecozone+comes from the joint CWS/USFWS Waterfowl Breeding Population and Habitat Survey. The waterfowl found in the Prairies are diverse, with a variety of different habitat requirements and migratory strategies -- some winter on Canadian coasts while the majority winter in the United States and Mexico (Bellrose, 1980). Although the Prairie Pothole Region covers only 10% of the available breeding habitat for waterfowl in North America, it supports the highest densities of breeding waterfowl and can account for greater than 50% of annual continental duck production (Bellrose, 1980; U.S. Fish and Wildlife Service, 2007). The Prairie Ecozone+ is also an important area for migrating waterfowl. Many ducks and geese that nest in the Arctic, sub-Arctic, and boreal forest pass through this ecozone+ during migration, stopping in staging areas.

Some waterfowl species show long-term population increases. For example Canada Goose populations increased by 765% since the 1970s (Table 16). Other species, such as Northern Pintail and American Wigeon, have declined significantly, while others, such as Blue-winged Teal and Canvasback, showed little long-term change (Table 16, Figure 16 and Figure 17).

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Table 16. Abundance trends for selected breeding waterfowl species in the Prairies Ecozone+.
SpeciesNesting habitatTrend (%/yr)PAnnual Abundance Index
(in 1000s)

1970s
Annual Abundance Index
(in 1000s)

1980s
Annual Abundance Index
(in 1000s)

1990s
Annual Abundance Index
(in 1000s)

2000s
Annual Abundance Index
(in 1000s)

% change
CanvasbackOverwater0.3 198146.7192.7206.24.2
RedheadOverwater0.7*279.2202285.1307.510.1
Ring-necked DuckOverwater0.6n47.455.244.157.320.8
Ruddy DuckOverwater1.6*145.5152.7196.7234.861.3
BuffleheadCavity2.7*59.455.592.9112.789.9
Northern PintailGround-4.1*2795.3944.8816.8835.5-70.1
American WigeonGround-3.6*908.6398.3356.7299.6-67
Green-winged TealGround-1.5*561.3220.7346.7323.8-42.3
MallardGround-1.1*3180.118012156.92221.2-30.2
Blue-winged TealGround-0.1 2024.51242.21636.81835-9.4
GadwallGround1.1*814.6585.2968.4986.621.1
Northern ShovelerGround1.2*899.9654.71022.9125439.3
Canada GooseGround7.9*47.7107.9238.6412.4765.4

P is the statistical significance: * indicates P<0.05; n indicates 0.05<P<0.1; no value indicates not significant
Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

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Figure 16. Population trends of selected ground nesting ducks (American Wigeon, Blue-winged Teal, Gadwall, Mallard, Northern Pintail, and Northern Shoveler) and Green-winged Teal in the Prairies Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 16

This line graph shows population trends of selected ground nesting ducks (American Wigeon, Blue-winged Teal, Gadwall, Mallard, Northern Pintail, and Northern Shoveler) and Green-winged Teal in the Prairies Ecozone+ from 1970 to 2006. American Wigeon and Northern Pintail populations have declined significantly during this period, from approximately 1,000,000 to 350,000 and 3,400,000 to 1,390,000. Mallard and Blue-winged Teal populations fluctuate annually, but follow a similar general decreasing trend from the mid-1970s to 1980s, then increasing to populations of approximately 2,400,000 and 1,600,000, respectively, with the Blue-winged Teal showing little long-term change. Gadwall population also fluctuates annually, peaking around 1,450,000 in 1998. Northern Shoveler and Green-winged Teal populations vary around 930,000 and 370,000 respectively.

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Figure 17. Population trends for breeding Canada Goose and selected over-water nesting ducks (Canvasback, Redhead, Ring-necked Duck, and Ruddy Duck) in the Prairies Ecozone+, 1970-2006.
Graph

Source: data from CWS/USFWS Waterfowl Breeding Population and Habitat Survey

Long Description for Figure 17

This line graph shows population trends for breeding Canada Goose and selected over-water nesting ducks (Canvasback, Redhead, Ring-necked Duck, and Ruddy Duck) in the Prairies Ecozone+ from 1970 to 2006. Canvasback showed little long-term change, fluctuating between approximately 82,000 and 440,000 during the period. Canada Goose populations showed increasing trends from about 40,000 in 1970 to 440,000 in 2006. Redhead and Ring-necked Duck population trends varied greatly, between approximately 15,000 to 44,000, and 11,000 to 101,000, respectively.

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Canada Geese appear to easily adapt to a variety of habitats including farmland and urban areas, likely benefitting from the conversion of deciduous forest and natural prairie to these land cover types by taking advantage of cereal grain, planted forage, and turf grass food sources (Mowbray et al., 2002). Similarly, management practices, such as re-establishment of local populations by relocating moulting adults and juveniles from other locations, has benefitted Canada Goose populations (Nieman et al., 2000; Mowbray et al., 2002). The population increase observed in the Prairies is consistent throughout the breeding range of the temperate breeding goose (Canadian Wildlife Service Waterfowl Committee, 2008).

Intensification of agricultural practices, including decreased use of summerfallow and increased conversion of marginal land to cropland, over the last 40 years has likely had negative impacts on breeding waterfowl on the Prairies through habitat loss and changes in predation patterns. For example, nest success for Mallard, Northern Pintail, Northern Shoveler, Blue-winged Teal, and Gadwall in the Prairie Pothole Region is negatively associated with the proportion of cropland (Drever et al., 2007) Landscape-level fragmentation has also increased (Stephens et al., 2003). Some avian species in southern Alberta were found to respond to habitat characteristics at spatial scales similar to their home range and territory size (with the exception of Northern Pintail), suggesting that fragmentation effects may vary with home range or territory size of individual species (Koper and Schmiegelow, 2006). Northern Pintail prefer to nest in sparse cover away from water, often in standing stubble, mulched stubble, or fallow fields early in the nesting season often prior to cultivation and planting (Austin and Miller, 1995). Since the 1970s, summerfallow has been increasingly converted to annual cropping, with fallow land being reduced by nearly 4 million hectares from 1971 to 1995 (Statistics Canada 1995 cited in Carlyle, 1997), and reduced from comprising 17.7% of agricultural land in 1986 to 7.3% in 2006 in the Prairie Ecozone+ (Javorek and Grant, 2011). This reduction in fallow land has been linked to the declining prairie population of Northern Pintail (Austin and Miller, 1995; Podruzny et al., 2002). Waterfowl nest success early in the breeding season was found to be lower in unmanaged nesting cover types (for example, cropland, hay land, and pasture) compared to managed cover (for example, delayed grazing, planted cover, idled pasture, and idled parkland) (Emery et al., 2005). Hoekman et al. (2002) suggested that, when comparing vital rates at various stages of the annual cycle, predation processes on the breeding grounds, inferred by nest success and female survival during the breeding season, is the primary proximate factor limiting population growth of midcontinent Mallards.

Climatic conditions also have a large impact on waterfowl populations in the Prairies. The protracted wide scale prairie drought in the 1980s had negative effects on waterfowl populations, although many species have since steadily increased (Table 16). Wetland abundance and distribution affects several demographic vital rates of prairie breeding ducks, including nesting intensity, brood survival, and adult survival (Krapu et al., 1983; Cowardin et al., 1985; Krapu et al., 2000; Devries et al., 2003), in addition to settlement and return rates (Johnson and Grier, 1988; Dufor and Clark, 2002). Northern Pintail, Blue-winged Teal, Mallard, and Northern Shoveler breeding densities fluctuated with numbers of prairie ponds, suggesting that these species fly over the Prairies in drought years and settle in more northern ecozones+ (Johnson and Grier, 1988). These species, along with Green-winged Teal, are dabbling ducks that are typically associated with shallow temporary and seasonal wetlands. Consequently, some of these species may be more sensitive to fluctuating water conditions (including wetland densities) and wetland destruction than other species, such as Gadwall and diving ducks (such as Canvasback and Ruddy Duck), which are associated with semi-permanent and permanent wetlands. As such, duck species that use small wetlands prone to agricultural modification or destruction and climate fluctuations are generally the species showing population declines (Table 16).

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