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I. Introduction

Reproduction in birds is generally timed so that the breeding cycle coincides with maximum availability of food for nesting adults or developing young (Immelmann, 1971). Food availability to birds can vary widely within and between years, however, with major implications to reproductive success (Pitelka et al., 1955; Kahl, 1964; Simmons et al., 1986). Recruitment among waterfowl may be particularly sensitive to the quantity and quality of food resources available, because the energy and nutrient requirements of egg-laying females are large relative to those of other bird species. In this chapter, we describe adaptive strategies of waterfowl for meeting nutrient requirements for reproduction and assess the significance of food in regulating reproductive performance. Our primary focus is on waterfowl occurring in the United States, Canada, and western Europe because most of the literature on waterfowl feeding ecology is from research conducted on Northern Hemisphere species.

Krapu, Gary L., and Kenneth J. Reinecke.  1992.  Foraging ecology and nutrition.
     Ecology and Management of Breeding Waterfowl.  University of Minnesota
     Press, Minneapolis, MN.  Chapter 1:1-29.

Krapu, Gary L., and Kenneth J. Reinecke.  1992.  Foraging ecology and nutrition.
     Ecology and Management of Breeding Waterfowl.  University of Minnesota
     Press, Minneapolis, MN.  Northern Prairie Wildlife Research Center Online. 
     http://www.npwrc.usgs.gov/resource/birds/ecomanag/foraging/foraging.htm
     (Version 02FEB99).

Table of Contents

• Historical Perspective
  • The Feeding Ecology of Breeding Ducks
  • The Feeding Ecology of Prebreeding and Breeding Swans and Geese
• Research Methods
  • Methods Common to Most Studies of Feeding Ecology
  • Methods Specific to Studies of Geese and Other Herbivourous Waterfowl
• Timing of Nutrient Acquisition
  • Swans and Geese
  • Ducks
• Food Habits
  • Swans and Geese
  • Ducks
• Factors Influencing Food Use
  • Evolved Patterns of Habitat Use and Morphology
  • Short-Term Variation of Food Availability
  • Nutrient Sources
    • Protein
    • Fat and Energy
    • Minerals
  • Foraging Energy
  • Competition
    • Intraspecific Competition
    • Interspecific Competition
• Proximate Effects of Food Resources on Reproduction
  • Timing of Reproduction
  • Failure to Breed
  • Clutch Size
  • Egg Mass and Composition
  • Egg Fertility and Hatchability
  • Occurence and Frequency of Renesting
• Effects of Agricultural Development on Food Resources
  • Geese
  • Ducks
• Research Needs and Oppotunities
  • Observational Studies
  • Laboratory Experiments
  • Field Experiments
  • Natural Experiments
• Acknowledgments
• References

Figures

• Figure 1-1 -- Composition of the diet of female ducks (Subfamily Anatinae) during the laying stage of the reproductive cycle.
• Figure 1-2 -- Spatial segregation of the principal foraging habitats of waterfowl tribes with respect to water depth and wetland plant communities.
• Figure 1-3 -- Temporal changes in the abundance of macroinvertebrate populations inhabiting a seasonal wetland in North Dakota (after Swanson et al., 1974).
• Figure 1-4 -- Nutrient composition of selected foods in the prebreeding and breeding diets of geese and ducks.

Tables

• Table 1-1 -- The contribution of endogenous protein, fat, and calcium to egg production in selected North American waterfowl.
• Table 1-2 -- Foraging effort by female geese during the breeding season.
• Table 1-3 -- Diurnal foraging effort (%) of ducks during the breeding season.
• Table 1-4 -- Principal foods of North American geese during the breeding season.
• Table 1-5 -- Percentage of macroinvertebrates (esophageal contents only) in the diets of female ducks during the breeding season.
• Table 1-6 -- Digestibility of selected foods of prebreeding and breeding geese.
• Table 1-7 -- Calcium and phosphorus concentrations (% of dry wt.) of selected foods consumed by breeding waterfowl.