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Researchers Examine Waterfowl Foods in Delta

The lower Mississippi alluvial Valley (MAV), or Delta as we call it in Mississippi, once was a 22-million acre bottomland hardwood forest, extending from southeastern Missouri to southern Louisiana. These bottlomlands flooded regularly between fall and spring and provided vast habitats for migrating and wintering waterfowl. During the 20th century, the Delta has been converted from lowland forests to farmland. Despite vast landscape and watershed changes, it remains a critical region for North American waterfowl, especially mallards. With most of the bottomland hardwood forests gone, but millions of ducks and geese still using the Delta, winter-flooded rice fields and moist-soil habitats have become increasingly important for sustaining waterfowl populations and hunting opportunities.

Rice seeds are high in energy, providing "fuel" for waterfowl to offset the costs of migration and survival during the cold weeks of winter. Moreover, waste grains left in rice fields after harvest resist decay, thus providing nutritious forage for ducks and geese during winter. Additionally, rice fields, with their levee systems, lend themselves readily to conversion to wetlands for winter waterfowl.

Research suggests that well-managed moist-soil habitats can provide more food and potential for waterfowl use than harvested croplands and forested wetlands. Moist-soil habitat management entails active manipulation of soil, "seed banks" in the soil, and water to promote seed and tuber production by a wide variety of natural plants such as grasses, sedges, and smartweeds. Recent research conducted at Mississippi State University (MSU) has revealed that moist-soil plant seeds and tubers can provide, on average, about 80% of the energy that waterfowl glean from agricultural seeds. Thus, well managed moist-soil impoundments can produce energy-rich and nutritionally diverse forage for waterfowl.

While rice fields and moist-soil habitats are important feeding sites for waterfowl, precise estimates of food availability in these wetlands are lacking. An abundance of "waste rice" (as high as 450 lbs/ac) exists in fields after harvest. However, recent studies by MSU researchers in Mississippi rice fields revealed that waste rice decreased by 79-99% between harvest and December, when waterfowl typically arrive in large numbers. A reliable estimate of rice density for the entire Delta is needed to guide waterfowl habitat conservation planning in this region. Similarly, estimates of availability of moist-soil plants in managed impoundments are few. MSU is investigating these issues through a project funded by several partners, including the Mississippi Department of Wildlife, Fisheries and Parks (MDWFP).

From September 2000-December 2001 researchers sampled 110 rice fields throughout the Delta in Arkansas, Louisiana, Mississippi, and Missouri and extracted 3,780 earthen cores from these fields to estimate availability of rice seeds. Preliminary results indicated a 72% decline in seed density from harvest (243 lbs/ac or 5.4 bushels/ac) through early December (67 lbs/ac or 1.5 bushels/ac). This early winter estimate is lower than estimates from the mid-1980s, which are currently used to direct conservation planning for waterfowl habitat in the MAV. Therefore, the area of managed rice fields may be less than needed to support population goals of the North American Waterfowl Management Plan. If the trend in loss of rice during fall continues, effective management strategies to deter its loss must be identified and implemented in the Delta.

A pilot experiment was initiated in 2001 at the Delta Research and Extension Center in Stoneville to evaluate several techniques (e.g., burning, disking, and flooding stubble) for conserving waste rice in fields after harvest. Preliminary results suggest that burning stubble after rice harvest may show promise. We will repeat our experiments in 2002 and 2003 to identify the best management practices for saving rice seeds for waterfowl on managed public and private lands in the Delta.

In fall 2001, managed moist-soil impoundments were sampled at Morgan Brake, Noxubee, and Yazoo National Wildlife Refuges. Estimated seed density ranged from 234-345 lbs/ac, indicating well managed moist-soil habitats may provide seed resources similar to or surpassing those in harvested rice fields.

During fall 2002, data collection will continue for these research projects. If you're driving in the Delta and see a crew sticking silver exhaust pipes into rice fields to remove soil cores or mechanically vacuuming-up seeds from moist-soil habitats, don't think your eyes are playing tricks on you. Instead, you'll be witnessing MSU graduate students hard at work gathering data to put more "groceries on the table" for waterfowl in the MAV. WI

Joshua Stafford, Ed Penny, and Rick Kaminski (Mississippi State University), and Ken Reinecke (U.S. Geological Survey) all cooperate with MDWFP conducting waterfowl research in the Delta.

 

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