Nutrient additions by waterfowl to lakes and reservoirs: predicting their effects on productivity and water quality

Abstract

Lakes and reservoirs provide water for human needs and habitat for aquatic birds. Managers of such waters may ask whether nutrients added by waterfowl degrade water quality. For lakes and reservoirs where primary productivity is limited by phosphorus (P), we developed a procedure that integrates annual P loads from waterfowl and other external sources, applies a nutrient load-response model, and determines whether waterfowl that used the lake or reservoir degraded water quality. Annual P loading by waterfowl can be derived from a figure in this report, using the days per year that each kind spent on any lake or reservoir. In our example, over 6500 Canada geese (Branta canadensis) and 4200 ducks (mostly mallards, Anas platyrhynchos) added 4462 kg of carbon (C), 280 kg of nitrogen (N), and 88 kg of P y -to Wintergreen Lake in southwestern Michigan, mostly during their migration. These amounts were 69% of all C, 27% of all N, and 70% of all P that entered the lake from external sources. Loads from all external sources totaled 840 mg P m-2 y '. Application of a nutrient load-response model to this concentration, the hydraulic load (0.25 m y -'), and the water residence time (9.7 y) of Wintergreen Lake yielded an average annual concentration of total P in the lake of 818 mg m 3 that classified the lake as hypertrophic. This trophic classification agreed with independent measures of primary productivity, chlorophyll-a, total P, total N, and Secchi disk transparency made in Wintergreen Lake. Our procedure showed that waterfowl caused low water quality in Wintergreen Lake.

Waterfowl Impoundments as Sources of Nitrogen Pollution

“…The capacity for waterfowl to serve as nutrient vectors has been studied across a variety of aquatic habitats (Chaichana et al 2010;Manny et al 1994;Olson et al 2005;Post et al 1998). Waterfowl at Lake Mattamuskeet, particularly Snow Goose (Chen caerulescens) and Tundra Swan (Cygnus columbianus), feed in adjacent wetland or agricultural habitats, but return to the Lake to roost where their defecation represents an allochthonous source of N. While we lack highresolution quantitative data on the movement of all species of waterfowl, we observed a consistent daily influx of geese, Tundra Swan, and ducks into the lake and impoundments at dusk.…”

“…We assume these populations are present at the lake for a season of 105 days (mid-November to mid-March) (Baldassarre et al 2006), use Manny et al (1994) ) and assume that this rate scales allometrically across species by body mass (Nagy et al 1999). We use the following body masses: Tundra Swan, 6.75 kg (Limpert and Earnst 1994); Atlantic Canada Goose, 4.6 kg (Mowbray et al 2002); Snow Goose, 2.6 kg (Mowbray et al 2000); and Mallard mass for ducks, 1.2 kg (Drilling et al 2002).…”

“…Since high bird densities are associated with elevated surface water nutrients (Gould and Fletcher 1978;Manny et al 1994;Olson et al 2005;Post et al 1998), the potential exists for heavy nutrient loading from impoundments that attract large flocks of waterfowl. An investigation into the potential water-quality impacts of waterfowl at a refuge in New Mexico concluded that waterfowl impoundments have the potential to export both N and P based on observed increases in concentrations from inflow to outflow (Brandvold et al 1976).…”

Food Dispersion and Foraging Energetics: A Mechanistic Synthesis for Field Studies of Avian Benthivores

“…Estimates of food requirements that do not consider the spatial pattern of food intake have unclear ecological implications, especially for animals that forage over large areas. For example, nutrients excreted by eiders and gulls in the Gulf of St. Lawrence are unimportant to the Gulf's total nutrient budget, but input by birds at aggregation sites can be locally significant (Bedard et al 1980; see also Ruess et al 1989, Powell et al 1991, Manny et al 1994). Shorebirds switching prey as profitability changes with prey depletion can alter the structure of invertebrate communities (Schneider 1978); and patchy herbivory can affect plant dispersion quite differently from more continuous grazing (Andrew and Jones 1990, Hyman et al 1990).…”

Evaluation of resident Canada goose movements to reduce the risk of goose‐aircraft collisions at suburban airports

“…Geese contaminate water sources (Manny et al 1994, Allan et al 1995, degrade habitat, can be aggressive toward humans (Smith et al 1999), and may have the potential to transmit diseases (Graczyk et al 1998, Smith et al 1999, Kullas et al 2002, Rutledge et al 2013. Additionally, resident Canada geese pose a threat to human safety near airports.…”