US Geological Survey

 

Date of this Version

2008

Citation

The Journal of Wildlife Management, Vol. 72, No. 6 (Aug., 2008), pp. 1383-1387

Comments

This article is a U.S. government work, and is not subject to copyright in the United States.

Abstract

The Mississippi Alluvial Valley (MAV), USA, is an internationally important migration and wintering region for North American waterfowl (Reinecke et al. 1989). The Lower Mississippi Valley Joint Venture (LMVJV) assumes food availability is the primary factor influencing carrying capacity of wintering waterfowl in this region (Reinecke and Loesch 1996). Because much of the MAV was converted from a seasonally flooded bottomland-hardwood ecosystem to a landscape dominated by agriculture, the LMVJV has incorporated estimates of the abundance of agricultural seeds such as rice into habitat conservation plans (Reinecke et al. 1988, Fredrickson et al. 2005). Biologists designed these plans to provide sufficient food when waterfowl populations attain levels of abundance targeted by the North American Waterfowl Management Plan (Lower Mississippi Valley Joint Venture Management Board 1990, Reinecke and Loesch 1996). Rice is an important crop in the MAV (i.e., >800,000 ha planted in the MAV of AR, LA, MS, and MO in 2003 and 2004 [National Agricultural Statistics Service 2004]) and is an energy-rich food for waterfowl (Reinecke et al. 1989). Manley et al. (2004) reported that rice lost before or during harvest (hereafter waste rice) in Mississippi fields was less abundant in early winter than previously estimated in the 1980s (i.e., 180 kg/ha [dry mass]; Reinecke and Loesch 1996). To obtain a contemporary estimate of the abundance of waste rice for conservation planning by the LMVJV, Stafford et al. (2006) sampled >150 harvested fields throughout the MAV and reported that waste rice averaged only 78 kg/ha in early winter 2000-2002. Knowledge of decreased availability of waste rice is crucial because, when rice abundance declines to approximately 50 kg/ha, energetic costs may exceed nutritional benefits of foraging and ducks may cease or give-up feeding in rice fields (Reinecke et al. 1989, Rutka 2004). Thus, the difference between waste-rice abundance in early winter and the giving-up density of 50 kg/ha is/ha, and waterfowl carrying capacity of harvested rice fields is