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Compilation of Focus Teams and Hydrogeomorphic Advisory Team Recommendations:
Shorebirds and Waterfowl Focus Team Recommendations

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Contents

Plant Focus Team Recommendations

Fish and Aquatic Invertebrate Focus Team Recommendations

Mammals, Amphibians, Reptiles and Terrestrial Invertebrates Focus Team Recommendations

Shorebirds and Waterfowl Focus Team Recommendations

Other Birds Focus Team Recommendations

Integrating Abiotic Factors in the Goals Project: Tenets of the Hydrogeomorphic Advisory Team

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Notice

The following is a compilation of the recommendations produced by each of the focus teams and the HAT. You will note that some of the terminology used in these reports differs from that used in the Goals Report. For example, some teams discuss regions and subregions that are defined differently, and some use different names for habitats. This is because the terminology used within the Project has evolved over time, and some has been developed specifically to facilitate presentation of the Goals.

In order to preserve the original intent of the focus team authors, no changes, other than minor formatting changes, have been made in the teams' reports. We believe the intent of their recommendations is made clear by the information contained in the reports.

Shorebirds and Waterfowl Focus Team Recommendations

This paper summarizes the Shorebirds and Waterfowl Focus Team's habitat recommendations. Included are our focus team tenets, some brief information regarding each of the key species, and habitat recommendaitons. We also have included some of the research needs that we believe need to be addressed. For additional information regarding the shorebirds and waterfowl species that utilize the baylands and adjacent habitats, please refer to the individual species narratives that will be compiled in the Goals Project's Focus Team Species/Community Narrative Report.

Introduction

Shorebirds and waterfowl are characterized by their mobility and strong dependence on aquatic and wetland habitats. The San Francisco Bay estuary is renown as a major North American refuge for many species of shorebirds and waterfowl during their migration and wintering (August through April) periods, and it provides breeding habitat during the summer for a few species (e.g. snowy plover, mallard). The estuary is recognized as a Western Hemisphere Shorebird Reserve Network site of international importance for more than a million shorebirds (Kjelmyr et al. 1991, Pt. Reyes Bird Obs., unpubl. rep.) and as the winter home for more than 50% of the diving ducks in the Pacific Flyway (Accurso 1992) with one of the largest wintering populations of canvasbacks in North America.

The current populations of shorebird and waterfowl species are a reflection of alterations in the development of the estuary (see Nichols et al. 1986) which may have resulted in increased numbers of some of these species while other populations have decreased. We do not know how many distinct populations depend on the habitats of this ecosystem and contribute to diversity and stability of continental populations. For example, northern pintails in the South Bay have little interchange with birds in the Central Valley, and they may represent a distinct subpopulation (M. Miller, USGS, pers. comm.). Western sandpipers show strong site fidelity to small areas in the South Bay and do not leave that subregion during the winter (Warnock and Takekawa 1996).

The loss of more than 90% of the wetlands in the estuary have greatly altered the ecosystem, which has resulted in the proposed listing or protection of more than one hundred species, many associated with tidal salt marsh habitats. Many projects to rehabilitate or restore wetlands in the estuary, especially tidal salt marsh, have been proposed to benefit listed species.

However, results of wetland restoration efforts are highly variable (Race 1985), and the efforts to complete successful salt marsh restorations for certain species may come at the expense of shorebird and waterfowl populations that use the existing habitats, including salt evaporation ponds. We lack specific information relating abundance of current populations to the amount of their habitats (for more specific information, see the individual narratives). Thus, we are unable to predict how reduction of present wetland habitat used by these species may affect their populations. We advise care in implementing large scale changes and encourage further study of critical habitats and better delineation of the regional populations present in the ecosystem.

Tenets

1. There should be no net loss of shorebird and waterfowl resources and populations in the ecosystem.

2. The San Francisco Bay ecosystem has been altered, and we will not be able to return it to historic conditions, nor is that necessarily desirable. Some habitats have actually increased from historic levels in some areas.

3. Shorebirds and waterfowl species are unlikely to benefit from tidal marsh conversions when the conversion is from another wetland type. As conversions do occur, we must enhance the remaining habitats for shorebirds and waterfowl.

4. Engineered tidal marsh and nontidal wetland and salt pond restorations have unpredictable outcomes. In fact, this field is very young and few restorations have been deemed to be successful.

5. No large conversions should be undertaken without pilot projects in advance. These pilot projects should include testing habitats and elements of habitats which replace lost habitat values for shorebirds and waterfowl.

6. San Francisco Bay is a crucial area within the Pacific Flyway. The region is as important to continental shorebird and waterfowl species as are specific parcels to endemic populations within the estuary.

7. Critical habitats for shorebirds and waterfowl include tidal flats, sparsely vegetated wetland elements (levees, islets, beaches), managed wetlands, salt evaporation ponds (which are not inherently bad as wildlife habitat and have increased some species while preserving areas from development); large, persistent seasonal ponds with lots of open water; and inactive salt ponds.

8. Managed wetlands (water control, predator control, muting tidal flows) may be more beneficial than natural wetlands in some cases.

9. Disturbances and flight obstructions (e.g. power lines) between feeding and roosting areas should be minimized.

10. Seasonal wetland have important habitat values for shorebirds and waterfowl, but are poorly quantified or understood. More research is needed to clarify how the habitats are used and how much is needed for sustaining populations.

Shorebirds

Shorebirds are aquatic birds with cylindrical bills varying considerably in length and curvature among the 31 species encountered regularly on San Francisco Bay. These species, which range from the sparrow-sized Least Sandpiper to the duck-sized Long-billed Curlew, feed primarily on invertebrates obtained on tidal flats, salt ponds, managed wetlands and other habitats. Recent survey information collected by Point Reyes Bird Observatory indicates that San Francisco Bay supports very high numbers of shorebirds of most species during migration and winter, compared to other wetlands along the U. S. Pacific coast. San Francisco Bay has been recognized as a site of hemispheric importance to shorebirds by the Western Hemisphere Shorebird Reserve Network.

Key Species

We selected seven "key" species as a basis for defining regional wetland habitat goals for shorebirds and provide detailed information on these species in the species accounts. Five species represent groups of shorebirds that use specific habitat types, one (snowy plover) is federally listed as a threatened species, and one (red knot) is especially dependent on San Francisco Bay as a wintering area.

Western Sandpiper (Calidris mauri) The western sandpiper represents small sandpipers and plovers, including least sandpiper, dunlin, and semipalmated plover. The western sandpiper is the most abundant shorebird in the Bay at all seasons. The least sandpiper and dunlin are also abundant. All four species breed in Arctic or sub-Arctic regions and occur in San Francisco Bay both as migrants and winter residents. On the Bay, tidal flats are their most important feeding habitat. At high tide these birds are forced from the tidal flats to roosting and auxiliary feeding areas including salt ponds, managed wetlands, and seasonal wetlands.

Marbled Godwit (Limosa fedoa) The marbled godwit was the selected representative for the large sandpipers and plovers which include willet, long-billed curlew, whimbrel, black-bellied plover and American avocet. These species breed in Arctic, sub-Arctic or temperate regions and occur in San Francisco Bay both as migrants and winter residents. Hundreds of avocets also breed in San Francisco Bay, primarily in salt ponds. Tidal flats are the most important foraging habitat of all these species except possibly the avocet which also forages extensively in salt ponds. At high tides these birds move from the tidal flats to roost in salt ponds, managed wetlands, seasonal wetlands and other habitats above the high tide line.

Red Knot (Calidris canutus) Although not abundant, the red knot was selected as a key species because San Francisco Bay is one of only three wetlands on the Pacific coast of North America supporting as many as several hundred wintering individuals. Red knots are Arctic breeders which occur in the Bay during migration and in winter. They often associate with black-bellied plovers and short-billed dowitchers but are more restricted than these species in their distribution within the Bay. Tidal flats of the Central and South Bay are the knots' primary foraging habitats and salt ponds serve as the primary high tide roosting habitat.

Long-billed Dowitcher (Limnodromous scolopaceus) The long-billed dowitcher was selected because of its use of fresh and brackish habitats. In addition to tidal flats, managed wetlands and seasonal wetlands are important foraging habitats for long-billed dowitchers and its associates. The other species associating with long-billed dowitchers in managed and seasonal wetlands are greater and lesser yellowlegs, dunlin, black-necked stilt and American avocet. This group of shorebirds was singled out as potentially deriving more benefit from managed brackish water wetlands and seasonal wetlands than other shorebirds. Managed wetlands also are used by two members of the group, black-necked stilt and American avocet, for nesting. Although not closely associated with any of the above species, because of its more solitary nature and preference for more vegetated habitats, the common snipe is the other shorebird which makes heavy use of the managed and seasonal wetlands as foraging and roosting habitat during winter.

Black Turnstone (Arenaria melanocephala) The black turnstone represents shorebirds that make the most use of gravel to rocky intertidal habitat. Also included in this group are ruddy turnstone, American black oystercatcher, wandering tattler, surfbird and spotted sandpiper. None of these species are abundant in the Bay, numbering at most in the tens to low hundreds of individuals at any time. Small numbers of American black oystercatchers regularly nest in the Bay as does an occasional pair of spotted sandpipers.

Snowy Plover (Charadrius alexandrinus nivosus) The Pacific coast population of western snowy plover was selected as a key species because it is federally listed as a threatened species. About 10% of the listed population has been recorded breeding on San Francisco Bay, primarily in South Bay salt evaporation ponds. Although there is no evidence this species bred in the Bay prior to the construction of the evaporation ponds, playas that existed on the inboard margins of the salt marshes prior to salt pond construction may have supported nesting snowy plovers.

Wilson's Phalarope (Phalaropus tricolor)The Wilson's phalarope was chosen to represent those shorebirds that, in addition to the snowy plover, are most dependent on the salt ponds for foraging habitat. Some members of this group, including the Wilson's and red-necked phalarope, occur only during spring and fall migration, while the others, including black-necked stilt and American avocet, are present year round. The latter two species also nest in the Bay, primarily in South Bay salt ponds but also in other areas of ponded water such as the managed wetlands of Suisun Bay. Surveys conducted by the Fish and Wildlife Service indicate that occurrence in salt ponds by these species is related to salinity, with the highest use by foraging stilts and phalaropes in ponds with salinities ranging from 130-180 ppt. Anecdotal historical information suggests that numbers of American avocets, black-necked stilts and Wilson's phalaropes have increased significantly since salt pond construction.

Habitat Considerations

Except for anecdotal information suggesting an increase in use of the Bay by shorebird species using salt ponds as their primary foraging or breeding habitat, there is no historic information on changes in abundance of shorebirds in the Bay during the past 150 years when most human-induced habitat alterations have occurred. The most recent mapping of historic and current Bay habitat by the San Francisco Estuary Institute (SFEI) indicates that tidal flats outboard of salt marsh have increased in the north and south subregions of the Bay, but that the total amount of tidal flat has decreased in all subregions, primarily due to loss of tidal flat along slough channels in salt marsh. Since the majority of the shorebirds in the Bay use tidal flat as their primary foraging habitat, foraging conditions in the Bay may have declined for these species unless gains in secondary foraging habitats such as salt ponds and managed wetlands have compensated for the tidal flat losses. Thus, the shorebird populations in San Francisco Bay may have declined commensurably.

For the majority of shorebirds that forage primarily on tidal flats, loss of subsidiary foraging areas such as salt ponds and managed wetlands might be mitigated (by an unpredictable degree) by creating wide, gently-sloped tidal flats along large channels in restored tidal marsh. Tidal salt marsh and slough channels do not, however, provide high tide roosting habitat for most shorebird species, which require barren to sparsely vegetated sites above the high tide line. Thus, suitable roosting areas will need to be constructed to replace roosting areas that are converted to tidal marsh. Roosting areas must be in reasonable proximity to tidal flat foraging areas (see Figure 1).

For the salt pond specialists substantial areas of salt pond habitat should be maintained in the north and south regions of the Bay. If portions of the salt pond systems of the north and south regions of the Bay are converted to tidal marsh and managed salt ponds, it will not be feasible to set aside ponds with important shorebird habitat in a piecemeal fashion. Instead smaller salt pond systems should be retained and re-engineered to produce salinities and water depths most favorable to shorebirds and the other aquatic species targeted for protection (see Figure 2). Low, wide, barren to sparsely-vegetated internal levees with fine scale topographic relief should be incorporated into the pond design as nesting and roosting substrate. In addition, salt marsh restoration efforts should attempt to recreate playas that occurred in historic salt marshes.

Since the success of marsh restoration efforts are likely to be highly unpredictable and the value of slough mudflats and salt marsh playa for shorebirds is not well understood, incorporation of these habitats into restored marshes should not be counted as replacement habitat for shorebirds. Further research must be undertaken to estimate the amount of salt pond habitat that should be managed for shorebirds and other target species. The maintenance of at least the current numbers of shorebirds relying extensively on salt pond habitat will require an adequate acreage of suitable ponds for 25,000 wintering American avocets, 5,000-7,000 wintering black-necked stilts, tens of thousands of migrating Wilson's and red-necked phalaropes in fall, and 300 breeding snowy plovers.

Waterfowl

The San Francisco Bay region is identified as one of the 34 waterfowl habitat areas of major concern in the North American Waterfowl Management Plan (US Fish and Wildlife Service 1989). More than 30 species of waterfowl are found in the San Francisco Bay ecosystem. These species are commonly divided into dabbling ducks, which feed at the surface or in shallow water to the depth of their body length, diving ducks, which forage underwater to 5 m in depth, and swans and geese which feed on plants by grubbing in sediments of wetlands or fields. Midwinter waterfowl surveys (US Fish and Wildlife Service, unpubl. data) of the San Francisco Bay and Delta include more than 700,000 waterfowl, and surveys of the open bays and salt ponds (Accurso 1992) include more than 300,000 individuals, a 25% decrease from the earliest surveys in the 1950s. In 1988-1990, dabbling ducks comprised up to 57,000 of the waterfowl in the open bays and ponds of the estuary, while diving ducks comprised up to 220,000 of the total. For this review, we selected six species as representative taxa of the waterfowl and the habitats they use in the San Francisco Bay ecosystem.

 See map, Figure 1: Tidal Flat Specialists (Dowitcher spp., Marbled Godwit and Western Sandpiper) Use of Tidal Flats

 See map, Figure 2: Ranking of South Bay Salt Ponds Based on Use by American Avocets, Snowy Plower, Black-necked Stilt, Phalaropes

Northern Pintail (Anas acuta) The northern pintail historically has been the most common dabbling duck in the ecosystem. Continental population declines have been severe, but even larger declines (90% in Suisun Marsh) have been recorded in the San Francisco Bay region. In addition, birds in the South Bay subregion may represent a distinct population that interchanges little with birds in the Central Valley (M. Miller, pers. comm.). Peak open bay numbers usually occur in October when dabbling duck numbers account for 50% of the waterfowl. Nearly 9,000 northern pintails are reported in October, with 5,000 ducks observed in midwinter. Maximum counts have exceeded 12,000 individuals. Pintails use a wide variety of habitats, including managed marsh, seasonal wetlands, open bay, and salt ponds. Species commonly found in similar habitats are green-wing teal (A. crecca), the northern shoveler (A. clypeata), and American wigeon (A. americana). American wigeon peak abundance includes 6,000 individuals or 1-2% of waterfowl in the open bays and salt ponds, but northern shovelers are the third most abundant species in the open bays and represent 13% of the waterfowl. Total dabbling ducks peak at over 50,000 birds, and represent 8-30% of total waterfowl.

Mallard (Anas platyrhynchos) Mallards are dabbling ducks with large economic and recreational importance as a hunted species and are commonly found in managed marshes. The mallard was selected as a representative of dabbling ducks such as Cinnamon teal (Anas cyanoptera) and Gadwall (Anas strepera) which migrate to the San Francisco Bay ecosystem during the winter. Gadwall numbers peak at 3,000 individuals, <1% of the waterfowl in the estuary. All three of these species represent resident breeding populations in the San Francisco Bay estuary as well. The largest population of mallards occurs in the Suisun Marsh subregion. Mallards have also been recorded as the most abundant dabbling duck in diked baylands of the San Pablo Bay and South San Francisco Bay subregions, most often using seasonal wetlands habitats and low salinity salt ponds.

Canvasback (Aythya valisneria) The canvasback is a diving duck that forages on aquatic plants or benthic invertebrates in mouths of rivers or channels, on large wetlands, or in brackish marshes. Sixty thousand individuals were counted in the mid 1960s, though historic populations were thought to be much higher. While the continental population of canvasbacks has not increased greatly in the last 20 years, based on mid-winter surveys (US Fish and Wildlife Service, unpubl. data) its population in the estuary has continued to decline. However, San Francisco Bay supports the largest population of canvasbacks (nearly 30,000 birds) on the Pacific Flyway and represents one of the three largest wintering areas in North America. Associated species that use similar habitats in the estuary include: common goldeneye (Bucephala clangula), greater and lesser scaup (A. marila and A. affinis), and very small populations of redhead (A. americana) and ring-necked ducks. San Francisco Bay is a major wintering area for scaup which have shown an unexplained continental decline in the past decade. Scaup comprised more than 40% of the open bay and salt pond waterfowl counted (Accurso 1992), up to 140,000 birds.

Ruddy Duck (Oxyura jaimaicensis) The smaller diving ducks of the estuary include the ruddy duck and bufflehead (Bucephala albeola) which use a variety of managed marsh areas and salt ponds in the baylands. The ruddy duck is widespread, but the population found in the San Francisco Bay ecosystem during the winter is one of the largest in North America. The maximum population has been estimated at about 28,000 birds. It is the fourth most abundant waterfowl species in the estuary, representing 7-8% of the total. As many as 7,000 bufflehead also are found in the estuary.

Surf Scoter (Melanitta perspicillata) Surf scoters are the least studied of the North American waterfowl. San Francisco Bay appears to be the most important inshore habitat in the eastern Pacific, south of the Straits of Georgia and Puget Sound. This species is representative of sea ducks that primarily use deeper, open-water, marine habitats. Associated species are white-winged scoters (M. fusca), black scoters (M. nigra), and red-breasted mergansers (Mergus serrator). Surf scoters are the second most numerous species in the ecosystem, with estimates as high as 73,000 birds in 1991 (Trost 1997, unpublished data).

Tule Greater White-fronted Goose (Anser albifrons gambeli) Tule geese were chosen as the key species to represent the geese and swans group which also includes Pacific greater white-fronted goose (Anser albifrons frontalis), Canada goose (Branta canadensis), Aleutian Canada goose (B.c. leucopareia), lesser snow goose (Chen caerulescens), and Tundra swan (Cygnus columbianus). Tule geese are associated primarily with managed wetlands and agriculture lands. The Suisun Marsh subregion is one of the few wintering areas in California and North America for tule geese. The geese and swans are of economic and recreational importance as four of the six members of this group are hunted, and overpopulation of geese may cause large urban and agricultural damage. Formerly, geese were present in the ecosystem in larger numbers but are now down to a remnant few, primarily in Suisun Marsh. For example, a population of what was perhaps a few hundred greater white-fronted geese which may have been the tule subspecies, now number less than 20 individuals in the North Bay (L. Allen, pers. comm.). Greater white-fronted geese are found primarily in Suisun and North Bay; Canada geese, all sub-regions; Aleutian geese, Suisun and Central Bay; snow geese, all sub-regions; and Tundra swans, Suisun and North Bay.

Habitat Considerations

Salt Evaporation Ponds - In 1988-1990, salt evaporation ponds supported 30-41% of the waterfowl in the ecosystem, 9-14% in the former North Bay ponds and 21-27% in the South Bay ponds. Many of the birds found in the estuary during migration (September-October, March-April) were found in these areas.

In the North Bay ponds, up to 42,000 diving ducks have been counted including 30% of the ruddy ducks in the estuary, 59% of the canvasbacks, and 38% of the bufflehead. As many as 15% of the dabbling ducks were also found in these ponds, including 19% of the northern pintail, and 47% of the mallards. Eighty-three percent of waterfowl were found in 54% of the salt pond area with salinities of 20-93 ppt, with most birds preferring 20-33 ppt areas. Pond size explained much of the variation in counts, with less than 2% of the use on small ponds < 150 ha, and most diving duck use on ponds 200 to 550 ha. South Bay salt ponds supported up to 76,000 or 27% of the estuary's total waterfowl. This area provided the largest haven for ruddy ducks (up to 67% of the population), and supported 17% of the canvasbacks, 50% of the bufflehead, and up to 86% (47,000) of dabbling ducks, including the majority (90%) of northern shovelers. Waterfowl were concentrated in lower salinity (20-63ppt) ponds, with few birds present in ponds above 154 ppt. Most waterfowl used ponds of moderate size, from 50 to 175 ha. Open Bay Areas - Up to 50% or 140,000 of the diving ducks surveyed in the estuary during the winter were counted in the North Bay subregion. Densities were as high as 653 birds/100 ha. The populations include up to 35% of the scoter, 26% of the canvasbacks, and 12% of the scaup. Most of the use was in water depths < 4 m, although much of the open bay area was less than 6m. The Central Bay supported 17% of the waterfowl, or up to 53,000 birds including 20% of the diving ducks. This area was important for scoter (up to 50%), scaup (16%), and bufflehead (13%), but only 1% of the dabbling ducks. The South Bay supported 9-11% or 36,000 of the waterfowl in the estuary, and was important for scaup (18%) and scoter (16%). The open waters of Suisun Bay supported only 12% of waterfowl in the estuary including up to 15% of the diving ducks (17% of scaup, 16% of scoter, and 16% of canvasbacks).

General Recommendations

It is important to maintain existing populations of shorebirds and waterfowl in the Bay while increasing habitat for other species that are dependent on salt marsh. Increasing the acreage of salt marsh will come at the expense of other habitats, especially salt ponds and managed wetlands that are important for shorebirds and waterfowl. Maintaining current shorebird and waterfowl populations will thus require increasing the carrying capacity of remaining salt ponds and managed wetlands or recreating their function in new locations.

Figure 3: Waterfowl Use of Salt Ponds in the North Bay Ordered from Most to Least Waterfowl Use

Reduction in the total salt pond area is related to the estimated decrease in waterfowl numbers. For examle, a 50% reduction in salt pond suggests a 24% reduction in waterfowl.

Subregions

Suisun Bay - Although these wetlands are managed primarily for waterfowl habitat by private land owners, populations of one of the major target species, northern pintail, have decreased by as much as 90%. Thus, despite the best management efforts, populations of waterfowl in the Suisun Marsh have decreased. Any conversion of managed wetland habitats will result in a loss of waterfowl. Conversion of this area should proceed gradually to provide time to evaluate population changes and the effects of the loss of habitat. Conversion or loss of this habitat type must be offset by enhanced management of existing areas or mitigation with alternative areas. Shorebirds are present in the tens of thousands. Management should be promoted to improve areas for their populations.

North Bay - The former salt evaporation ponds in this region are a critical area for shorebirds and waterfowl. Ongoing conversion should be linked to enhanced management of existing areas or mitigation. In this subregion, conversion of 50% of the former salt ponds may result in loss of 24% of the 42,000 waterfowl that are counted in these ponds (Figure 3)J. Takekawa, unpubl. data). Change in salt pond areas may already be resulting in reduction of waterfowl numbers (U.S. Fish and Wildlife Service, midwinter surveys, unpubl. data). Thus, there is an immediate need to develop alternative managed marsh areas in this subregion. Although mudflat habitats seem abundant in the North Bay, shorebird roosting habitats may be limiting and should be increased.

Figure 4: Waterfowl Use of Salt Ponds in the South Bay Ordered from Most to Least Waterfowl Use

Reduction in the total salt pond area is related to the estimated decrease in waterfowl numbers. For examle, a 50% reduction in salt pond suggests a 15% reduction in waterfowl (J. Takekawa, unpubl. data).

Central Bay - This subregion is highly urbanized and is used least by both shorebirds and waterfowl. Any additional roosting habitat that can be protected from disturbance would be beneficial in maintaining or improving existing populations. Restoration of any large, shallow ponds would likely benefit shorebirds and waterfowl. Wetland rehabilitation in urban areas should be encouraged.

South Bay - The majority of the shorebirds and waterfowl in the South Bay use the salt evaporation ponds for roosting or feeding habitat during the winter. Conversion or loss of this habitat type must be offset by enhanced management of existing areas or mitigation with alternative areas, including created salt ponds, managed wetlands, and seasonal wetlands. For example, analysis of waterfowl survey data from 1988-1990 (J. Takekawa, unpubl. data) suggests that if 50% of the salt ponds are converted, 15% of the 76,000 waterfowl may be lost (Figure 4). An increasing number of waterfowl would be displaced if more area was converted.

Although mudflat foraging habitat seems adequate, with salt pond conversion, suitable roosting habitat for shorebirds may become limiting. Little is known about how salt ponds and seasonal wetlands provide food for shorebirds and protected microclimate areas during adverse weather. Thus, we recommend not more than 50% or 15,000 acres of salt ponds in the South Bay be converted to other habitats without careful planning for habitat mitigation for shorebird and waterfowl populations. We also recommend an increase in seasonal wetlands as migration habitat and roosting areas.

Enhancing Tidal Marsh Restoration Projects for Shorebirds and Waterfowl

1. Shorebirds and waterfowl may use several elements in tidal salt marshes. As restoration or rehabilitation is undertaken, these elements should be provided when possible.

2. Larger channels with large mudflats are often used by shorebird and waterfowl species and should be encouraged in tidal marsh design.

3. Muted tidal areas provide temporal diversity which may provide good habitat, especially for diving ducks.

4. Unvegetated levees and islets with gradual slopes that are durable, and bare areas that remain unvegetated with limited management should be constructed as roosting sites.

5. A diverse mix of pans and ponds should be retained in marsh plains for high tide roosting and foraging areas.

6. Designs should be made to minimize disturbance by people, pets, and predators.

7. Surveys of shorebirds and waterfowl should be conducted prior to restoring areas to tidal salt marsh so losses may be evaluated and suitably mitigated.

Research Needs

Relationships among habitat change and change in populations of waterbirds have been studied in other estuaries (see Goss-Custard et al. 1997). We should learn from these efforts and develop a research program in the San Francisco Bay estuary to examine questions raised in the goals process including the following topics:

1. Determine the feasibility of designing ponds or systems from the existing salt evaporation ponds which can support the current populations of shorebirds and waterfowl.

2. Evaluate what constitutes a good roosting area for different species of shorebirds including distance from feeding areas. Areas used within tidal salt marshes should be included.

3. Estimate the size and composition of shorebird populations in Suisun Bay subregion.

4. Determine the importance of non-mudflat habitats such as salt ponds and seasonal wetlands as foraging areas, especially during inclement weather.

5. Examine seasonal wetland use and extent (not available in the EcoAtlas), including diked farmland, grazed baylands, diked marsh, managed marsh, and ruderal baylands through wet and dry years.

6. Test differences in shorebird and waterfowl response to different actions in managed wetlands by measuring use-days and numbers.

7. Relate diving ducks use of wetlands by area size and water depth.

8. Quantify shorebird foraging and roosting in wetlands other than intertidal flats, including intertidal pans, low and medium salinity ponds, managed marsh, diked marsh, muted tidal, and seasonal ponds. Include factors such as tidal cycle, salinity, vegetation, and distance to intertidal flats.

9. Describe use of wetlands by salinity and prey differences for shorebirds and waterfowl.

10. Provide more information about the effects of disturbance on shorebirds and waterfowl to develop suitable habitat buffer zones.

11. Determine the effects of channelization, levee alteration, and use of dredged-spoil on mobilization of contaminants sequestered in soils or sediments and bioaccumulation in shorebirds and waterfowl.

12. Characterize hydrology, biology, and chemistry of salt ponds heavily- and lightly-used by shorebirds and waterfowl to examine the differences.

13. Determine habitat values and use by waterfowl and shorebirds of managed wetlands versus tidal wetlands.

14. Investigate the effect non-native invertebrates and plants (e.g. Potamocorbula amurensis, Spartina alterniflora) on shorebirds and waterfowl.

15. Evaluate methods to reduce effects of non-native predators on shorebirds and waterfowl.

16. Examine the effects of contaminants on breeding birds.

17. Pilot Projects encourage monitored experiments in wetland restoration or mitigation:

a. Include repeatable waterbird surveys before and after project actions

b. Examine maintenance or creation of salt pond systems, including low to mid salinity ponds in the absence of commercial production. Habitat values and use should be maximized while minimizing maintenance costs. c. Test methods of constructing habitat elements with low maintenance requirements such as bare roosting islands, intertidal pans, and non-tidal seasonal ponds. d. Examine differences in use of different wetland unit sizes.

e. Test methods of increasing shorebird and waterfowl use of managed marshes.

f. Increase monitoring efforts on existing projects with habitat elements valuable for shorebirds and waterfowl.

g. Employ adaptive management by applying earlier findings to change design elements through time.

h. Preliminary sampling for contaminants of areas designated for salt marsh restoration.

i. Preliminary sampling of salt ponds for invertebrate community, salinity, and other water quality characteristics.

Literature Cited

Accurso, L. M. 1992. Distribution and abundance of wintering waterfowl on San Francisco Bay 1988-1990. Unpubl. Master's Thesis. Humboldt State Univ. Arcata, CA. 252 pp.

Goss-Custard, J. D., R. Rufino, and A. Luis (eds.). 1997. Effect of habitat loss and change on waterbirds. ITE Symposium No. 30 and Wetlands International Publ. No. 42. The Stationary Office, London.

Race, M. S. 1985. Critique of present wetlands mitigation policies in the United States based on an analysis of past restoration projects in San Francisco Bay. Environ. Manage. 9:71-82.

Nichols, F. H., J. E. Cloern, S. N. Luoma, and D. H. Peterson. 1986. The modification of an estuary. Science 231:567-573. Trost, R.E. 1997. Pacific Flyway 1996-97 Fall and Winter Waterfowl Survey Report. US Fish & Wildlife Service, Migratory Bird Management Office, Portland, OR. unpubl. data.

Warnock, S. E., and J. Y. Takekawa. 1996. Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary. Ibis 138:160-167.

United States Fish and Wildlife Service. 1989. Concept plan for waterfowl habitat protection. North American waterfowl management plan, category 27. U. S. Dep. Int., Fish Wildl. Serv. Rep., Portland, OR.