The Development and Delivery of Ducks Unlimited Conservation Programs in Priority Mid-Continent Waterfowl Migration and Winter Habitat Regions

The mission of Ducks Unlimited is to fulfill the annual life cycle needs of North American waterfowl by protecting, enhancing, restoring, and managing important wetlands and associated uplands. Ducks Unlimited has been conserving waterfowl breeding habitat since the Dust Bowl days of the mid-1930s and remains the only private conservation organization that contributes approximately $20 million US (which is leveraged via the USFWS and DU Canada to garner $4 additional dollars for every $1 US) to DU Canada for habitat conservation work on important breeding habitat.

During the 1970s and 1980s, waterfowl managers began to pose questions regarding the relationship of migration and winter habitat to the overall health of waterfowl populations. Such questions stemmed from that fact that most key winter and migration areas had lost significant habitat as a result of land use changes related to flood control, river navigation, agriculture, urban development, and other factors. Examples of such losses on the most important migration and winter habitats include the following:

Rainwater Basins (Nebraska): 91% of the wetland basins in this continentally important spring migration area have been drained and converted to other uses. The Rainwater Basins are the jumping off point or the last stop prior to arrival on prairie nesting areas, particularly for large numbers of mallards, pintails, white-fronted geese, Canada geese and snow geese. Several; species, particularly mallards and pintails, stage at this area until weather conditions moderate and ice cover dissipates enough to permit movement into breeding areas. Mallard and pintails must maintain fat reserves in these habitats that they subsequently use in formation of eggs during their first nest attempt.

Playa Lakes (Texas panhandle, extreme western Oklahoma and Kansas, extreme southeastern Colorado, and extreme northwestern New Mexico). Approximately 70% of playas larger than 10 acres have been modified to concentrate precipitation runoff for use in irrigation of crops. Many others suffer from siltation as surrounding lands are farmed in many cases up to the edge of the wetland basins. These wetlands undergo annual variation in availability comparable to wetlands in prairie nesting areas and are highly dependent on local precipitation. Habitat availability appears good in about 1 out of every 5 years. In some winters, like 2001-2002, the only playas containing water were those that captured the outfall of wastewater treatment plants and stockyards.

Missouri : Waterfowl used wetlands along the floodplain of the Missouri River as key migration and winter habitat. However, the natural hydrology of the Missouri and Upper Mississippi River hashave been dramatically altered for navigation and flood control. These alterations have contributed substantially to the estimated loss of 87% of Missouris wetlands. The Missouri and Mississippi Rivers have been disconnected from their flood plains via levees, while dams and navigation locks control much of the instream river flow. Consequently, important fall and spring migration habitat has been severely reduced along this continentally important migration corridor. Such habitats may be especially important for spring migrating waterfowl as females maintain fat reserves that are used in formation of the first clutch of eggs they will lay on prairie nesting areas.

Mississippi Alluvial Valley (extreme southern Illinois, western Kentucky and Tennessee, the Missouri bootheel, eastern Arkansas, northwestern Mississippi, and northeastern and northcentral Louisiana). The MAV, known regionally as the Delta, is the floodplain the Mississippi River. It is easily the most significant winter habitat area for mallards in North America, and it is probably the most important wintering area for mallards in the world. Additionally, it is of increasing importance to wintering and migrating pintails. Results of recent research performed at LSU indicate a January-February movement of female pintails northward into the MAV, which is likely a starting point for their northward migration each spring.

The MAV was once a 24.7 million acre complex of forested wetlands. Each winter, portions, and sometimes nearly the entire system, flooded, making several million acres of habitat available to wintering mallards and wood ducks in particular, as well as lesser numbers of gadwall and wigeon. Food in the form of acorns and other hard and soft mast, and moist soil plants such as wild millet, were made available via this winter flooding. While no wetland system is 100% reliable or predictable in terms of annual habitat and food availability, the MAV was likely among the most consistent and reliable habitats the birds encountered during their annual cycle.

Such is no longer the case. Approximately 80% of the forested lands in the MAV have been cleared and converted to agriculture, including thousands of acres that were cleared as recently as the 1970s when soybean prices made it economical to farm very marginal, flood-prone lands. Further, natural flooding in the MAV has been reduced by 50-90%. Systems such as the White River of Arkansas still undergo perhaps 50% of the flooding they sustained prior to alteration, whereas in the Big Sunflower River drainage in Mississippi, natural flooding has been reduced by nearly 90%. Hence, what was a system that provided reliable consistent winter habitat on an annual basis, today is a system that provides far less habitat than it did formerly, and the availability of that habitat is subject to far greater variation due to construction of levees, pumping stations, and flood storage reservoirs. Today, flooding occurs later in winter and well into the growing season (into June in some areas), the duration of flooding on some higher sites is far less to nonexistent, while flooding on some lower sites occurs much longer and later each year. The net effect of these alterations is significantly reduced availability of feeding habitat or forested habitats that provide for other needs of birds at this time of year, such as pair isolation, thermal refuge during cold snaps, etc.

Gulf Coast Prairies and Marshes (Louisiana and Texas). This region is another continentally significant winter and migration area for waterfowl, and like others mentioned herein, its ability to support waterfowl during migration and winter has been severely compromised. Louisiana provides some very disturbing examples of habitat alterations and outright loss. In recent history, Louisiana alone has had approximately 3.4 million acres of coastal marsh, within which were numerous highly productive marsh ponds that served as feeding and loafing areas for waterfowl.

Large scale alteration of coastal hydrology through construction of a main stem levees on the Mississippi River, the Intracoastal Waterway, and oil field exploration canals have drastically affected the Gulf Coastal marshes, particularly in Louisiana. During the past 50 years, marsh has been lost at a rate of 40 square miles annually, with a resulting loss of an estimated 900,000 acres. Loss rates have slowed in recent years to about 25-35 square miles/year, but projections for the next 50 years suggest an additional 630,000 acres of marsh and forested wetland will be lost despite intensive and expensive efforts geared toward protection and restoration in the coastal zone. Hence, of the original 3.4 million acres of marsh that occurred in recent history, approximately 1.53 million acres, or 45%, will be gone within about the next 50 years.

From the standpoint of waterfowl habitat, the outright loss of a huge area of feeding and resting habitat in the form of marsh ponds is complicated further by declines in rice production on the Gulf Coastal prairies. The coastal prairies consist of a narrow band of former grassland that has been converted to agriculture dominated in recent times by rice production. Waterfowl have adapted well to this land use change and have come to make extensive use of waste rice in harvested, flooded fields in this region. However, a number of factors including higher production costs, changes in Federal farm programs, and other factors have caused a fairly steep decline in land dedicated to rice farming in this region. For example in the Texas Mid-Coast, Texas Chenier Plain (southeastern TX) and the Louisiana Chenier Plain (southwestern Louisiana), rice production has declined 50%, 65% and 28% respectively since the mid-1970s. Generally, land has been converted to production of crops of no value (sugar cane) to waterfowl, or abandoned completely to be invaded and lost to exotic Chinese tallow trees (no value to waterfowl). Hence, from a high of nearly 1.2 million acres of rice as recently as 1968, production in 2000 in this region had dropped to approximately 536,700 acres, for a net loss of potential feeding habitat of 663,300 acres. It should be noted here that these losses are additive to marsh loss rates discussed above.

What do these losses of habitat mean for wintering and migrating waterfowl?

In 1970s and 1980s, waterfowl biologists in the scientific research community began to investigate habitat requirements of waterfowl on migration and winter areas. This research examined relationships between winter and migration habitat conditions, over-winter survival, winter physical condition (sampling to estimate variation in fat and protein levels), winter behavior, and several other aspects of waterfowl biology. When the results of these numerous studies are considered wholly, it appears the winter and migration habitat are important to waterfowl in some very obvious, and some not so obvious ways.

Various studies of several different species suggest that waterfowl spend somewhere between 20-70% of each day searching for and acquiring food during migration and winter. The amount of time spent feeding varies with many factors, including species, habitat type, habitat quality, ambient temperature, disturbance, pair status, and others. Given the large amount of time spent feeding during this period, it is evident that the most important aspect of habitat that managers should concentrate on is foraging habitat. By extension, an assumption is made that the amount of foraging habitat in a given region (e.g., the MAV, LA Gulf Coast Chenier Plain, etc.) limits the number of waterfowl that can winter there. Implicit in this assumption, is that if foraging habitat is limited in a particular region, there is a detrimental effect on over-winter survival that occurs because birds must be more mobile in search of food, they are in poorer physical condition, some birds will be displaced into suboptimal habitat areas, and ultimately, over-winter survival rates may be incrementally reduced, leaving fewer birds to return north for the subsequent nesting breeding season.

Because of the inherent natural variation in wetland habitat availability, most species of waterfowl store fat reserves that serve to provide energy during periods when food may be scarce. Mallards, for example, are able to store enough fat to forgo feeding for approximately 5-7 days. Fat storage amounts to an insurance policy the birds hold against the unpredictable nature of the habitats they use. There are costs to maintaining this energy reserve, but the benefits must outweigh the cost or such a pattern of fat storage would not occur.

Habitat conservation for waterfowl in winter, then, comes down to providing foraging habitat sufficient to allow attainment of daily energy needs and maintenance of an optimal level of fat reserves to use when habitat conditions become poor or food becomes scarce. Given the moderate to severe reductions in migration and winter habitat that has occurred in the important regions discussed above, it is clear that sound, science based waterfowl management should have as a goal to restore and/or maintain migration and winter habitat conditions that will support desired continental populations of waterfowl.

How do we estimate how much foraging habitat is needed in a particular region?

The North American Waterfowl Management Plan (NAWMP) essentially has a goal to restore and/or maintain breeding waterfowl populations so they are consistently, year in and year out, at the levels observed in the mid-1970s. The mid-1970s serve as target numbers since that is when inventories and indexes suggest populations were the highest since records have been kept beginning in the late 1950s. Given this over-riding goal, the next step was to determine what portion of that number of birds should be accounted for in various important wintering areas. Such estimates have been developed using harvest estimates, state and Federal surveys of winter populations, and other information. This process can be complicated, but in the end, biologists are typically able to arrive at a reasonable estimate of the number of birds, in some cases by species, that may be expected (or desired) to winter in a given region. For example, the MAV is expected to winter approximately 8 million ducks, while the Gulf Coast from Mobile Bay to South Texas and Laguna Madre should provide winter and migration habitat for 13.7 million ducks and 1.3 million geese when populations are near NAWMP objectives.

Given an estimated population, the next step in planning for conservation programs is to estimate approximately how many acres of foraging habitat will be needed to support the desired population in a given region. This exercise requires knowing how much food (energy) a duck requires on a daily basis, which is something we are able to estimate based upon the body size (mass) of the bird. We also know how much energy certain foods provide on a per unit weight basis (e.g., we know that rice grains provide a certain amount of energy per unit weight). Finally, with a few exceptions, we have estimated the amount of various waste grains or natural foods that occur on a per acre basis in a given region. Hence, given this information, it is a relatively simple mathematical calculation to estimate how many acres of habitat of various types are needed to meet desired population objectives.

In the MAV, it has been estimated that approximately 480,000 acres of managed harvested cropland (primarily rice and soybeans) and moist soil wetlands (natural vegetation) are needed to meet the food demands of the birds that would winter there when populations are at NAWMP objectives. The term managed means that managers would like to see 480,000 acres of water held in winter that is intended to provide foraging habitat for ducks, i.e., it is done purposefully with the use of water control structures. Notably, however, much of this habitat is rainfall dependent. No concerted effort is made to artificially flood these acres via pumping. Hence, the natural variation that always occurred in this particular system still occurs, at least to the degree it can given the drastic land use alterations. When conditions in the MAV are drier than average, waterfowl have to cope with these conditions much like they always have, by being mobile and finding suitable feeding areas, and using their fat reserves until such feeding habitat is located.

Along the Gulf Coast from Mobile Bay to Texas, an estimated 163,884 acres flooded harvested rice, and 251,404 acres of flooded natural emergent vegetation (a.k.a., moist soil plants such as wild millet, etc.) are needed to support desired populations. However, an assumption is made that 50% of that is already provided by landowners throughout the region. Hence, conservation plans for this particular priority area call for DU and its partners to flood approximately 81,942 and 125,702 acres of harvest rice and moist soil habitat, respectively. Another important aspect that is not included in these calculations is the amount of feeding habitat provided by coastal marsh ponds. These ponds present special problems discussed below.

Where are we with respect to these objectives?

DU evaluates project accomplishments and project performance annually. For clarity, accomplishments reflect acres enrolled in various conservation programs, which does not translate directly into acres flooded (this is performance). Accomplishments exceed performance because many, but not all, projects are dependent upon rainfall to flood, so during drier than average winters performance is lower than in average or wet years. In the MAV, for example, project performance on DU private lands projects is about 60% in average years, but may be as low as 30-40% in dry winters. We are gathering similar data for our work on the Gulf Coast of Louisiana and Texas.

DU is also in the process of assessing how much foraging habitat occurs on private lands outside the scope of our conservation programs. We are performing similar analyses on Gulf Coast agricultural habitats. Ultimately, we plan to estimate the acres provided outside of programs, within programs, and the annual variation in these acres as it relates to rainfall, and then determine how much more, if any, program accomplishments are required to meet foraging habitat objectives that will support desired population objectives in the MAV and Gulf Coast.

Along the Gulf Coast, one area for which we do not yet have enough information to understand the unit energy/area relationship is in coastal marsh ponds. Obviously, such habitat provides food for a substantial portion of waterfowl wintering in this region. Hence, DU is supporting, along with other partners, a research investigation at Louisiana State University aimed at developing estimates of the foraging habitat value of marsh ponds by salinity type. Put simply, we need to know, on average, how much food is available per unit area of marsh pond. We can take that information and estimate how many waterfowl can be supported via the marsh pond component of the Gulf Coast, combine that with estimates based upon agricultural habitats, and we will know with a reasonable degree of certainty how much habitat conservation we need to accomplish to support desired winter waterfowl populations.

It is an adaptive process.

These programs are based on solid science and the best available information. As we implement programs, we continually evaluate and try to learn more about the systems within which we work. Ultimately, we need to assure that sufficient foraging habitat is in place to provide for the NAWMP population goals and objectives. So, through this process we plan on the best available information, implement programs, and evaluate program effects and system variation related to important factors like precipitation. Information from evaluation efforts feeds back into conservation delivery through revisions to plans, with implementation proceeding until all partners are satisfied that habitat objectives are met and secured. This is the best way to develop, deliver and manage these programs in the face of uncertainty about the systems within which we work and the ducks we are committed to conserving.