Research

Duck Production and Agricultural Policy in the Prairie-parkland Region
by Mark Koneff, U.S. Fish and Wildlife Service

In highly modified landscapes such as the Canadian and U.S. prairie-parkland region (PPR), bird conservation is most effective when habitat acquisition and restoration are complemented by land-use policies providing extensive habitat benefits. Analyses of waterfowl breeding population and production survey data from the PPR (FIG. 1) indicate recent changes in the number and distribution of ducks produced. These changes may offer broad-scale evidence of the impact of intensive conservation initiatives and incentive-based land conservation policies when delivered in concert.

During the 1970s, brood indices from annual production surveys were variable but four times greater in Canada than in the U.S. PPR. Between 1972 and 1979, the ratio of broods to duck breeding population size, an index of reproductive success rate, averaged 0.0175 in Canada and 0.0166 in the United States. Through the 1970s and 1980s, the PPR gradually entered into widespread drought, and waterfowl populations declined substantially.

Alarmingly, there were indications that drought alone could not explain the magnitude of decline. Continued agricultural conversion of nesting habitats was thought to be exaggerating the effect of the drought. This, and other concerns about habitat degradation, ushered in a new era of partnership-based conservation through the signing of the North American Waterfowl Management Plan (Plan) in 1986. Moving aggressively, Plan partners in the United States and Canada restored or enhanced 3.1 million acres of grassland and wetland habitat in the PPR from 1986-1999.

Concurrent with Plan development, the United States instituted agricultural-land conservation provisions through the 1985 Food Security Act (Farm Bill). The Conservation Reserve Program (CRP), established by this act, provided incentives for farmers to idle marginal cropland by planting a dense grass-forb mixture, a habitat favored by nesting waterfowl. For most of the 1990s, CRP annually contributed approximately 4 million acres of nesting cover in the U.S. portion of the PPR, five times that achieved through direct conservation initiatives in the United States during the first 13 years of Plan implementation.

Above average precipitation in 1993 and 1994 restored favorable wetland conditions across the PPR and good conditions generally have prevailed since. From 1994 to 2000, brood indices and the ratio of broods to breeding population in the U.S. PPR averaged 246.1 thousand and 0.0280, respectively, compared to 174.0 thousand and 0.0131 in Canada (FIG. 2). During this period, pond density was high throughout the U.S. PPR, while conditions in Canada were good but more variable.

Recent U.S. brood indices, when compared with predictions based on pre-1991 pond and breeding population relationships, are higher than expected even given the recent wet conditions in the U.S. PPR (FIG. 3). While causation cannot be demonstrated, this does suggest that the millions of acres of nesting cover contributed by CRP and lesser amounts by the Plan have had a positive effect on duck recruitment. This apparent broad-scale impact serves to endorse Plan partner efforts to supplement acquisition and restoration programs by strengthening conservation provisions in subsequent Farm Bills and should encourage partners pursuing policy-based conservation opportunities in Canada.

For more information, contact Mark Koneff, U.S. Fish and Wildlife Service, Division of Bird Habitat Conservation, 11510 American Holly Drive, Room 301E, Laurel, Maryland 20708-4017, (301) 497-5648, mark_koneff@fws.gov.

Food for Ducks and Food for Thought
by Scott W. Manley, Ducks Unlimited, Inc. and Kenneth J. Reinecke, U.S. Geological Survey

Rice fields flooded by private landowners provide a very important foraging habitat for migrating and wintering waterfowl throughout the Mississippi Alluvial Valley (MAV). Waste rice is the most important food of ducks using these rice fields, but weed seeds and aquatic invertebrates are also readily used. Habitat conservation strategies of the Lower Mississippi Valley Joint Venture assume that waste rice on private fields will provide the largest proportion of the food needed during winter, when population goals of the North American Waterfowl Management Plan are achieved in the MAV.

A recent study conducted in the MAV of western Mississippi during winters 1995-96 and 1996-97 sampled 72 rice fields and a total of 1,275 hectares. Results indicated that the amount of waste rice remaining after fields were harvested during August to early October averaged 490 kilograms per hectare. However, by early December when fields began to flood and waterfowl arrived in significant numbers, the average amount of rice seed remaining was only 38 kilograms per hectare. The loss of waste rice between autumn harvest and early winter was more than 90%.

If these results reflect the current status of food resources on rice fields throughout the MAV, the role of private lands and other conservation strategies of the Joint Venture may need to be revised. The amount of waste rice available may be less than previously believed or the amount may vary across the MAV and among years. Perhaps, rice fields provide other habitat needs such as roosting areas and rice is a less important food resource than has been thought. If any one of these conditions is true, it has important planning implications for waterfowl conservation in the Lower Mississippi Valley.

The reasons for the decline in waste rice seed between autumn harvest and early winter are not fully understood. Because rice is now harvested as much as 100 days before waterfowl arrive, several factors may contribute to the losses. One possibility is that rice now is being harvested earlier in autumn when temperatures are higher. This may allow more rice seed to germinate following harvest. Consumption of rice by other wildlife and decomposition also may play a role.

To further our understanding of rice availability in winter, the contribution of rice fields to food requirements of waterfowl, and habitat conservation strategies of the North American Waterfowl Management Plan, a new cooperative study was initiated in winter 2000-2001. This research will determine the current value of flooded rice fields to foraging waterfowl and recommend management strategies to maintain this important habitat base in the future.

For more information, contact Scott W. Manley, Ducks Unlimited, Inc., 4511 East 43rd Street, North Little Rock, Arkansas 72117, (501) 955-9264, smanley@ducks.org.