The Food Preference Paradigm: A Review of Autumn–Winter Food Use by North American Dabbling Ducks (1900–2009)

Abstract

Studies describing food use (i.e., diet) of nonbreeding dabbling ducks Anas spp. are essential to understanding physiological needs of and recommending habitat management for these birds. We conducted a review of published autumn and winter food-use studies of dabbling ducks in North America to characterize the current state of knowledge and identify remaining research needs. We initiated our review to determine whether valuations of duck foods and the term “preference” commonly used by researchers and in waterfowl management guides (i.e., the food preference paradigm) were supported by available peer-reviewed literature. We analyzed peer-reviewed literature (1900–2009) on autumn–winter food use of dabbling ducks (n = 59 studies). Most studies (68%) used methods known to contain substantial bias including data from gizzards and hunter-collected ducks. Only 5% of published articles reliably determined food selection by concurrently measuring food use and availability, and no study determined food use at a scale appropriate for winter home ranges of dabbling ducks. In some habitats commonly managed for waterfowl (e.g., agricultural lands), few if any collections of ducks are available to obtain data on food use. The limited geographic and habitat scope of unbiased food use and selection studies for dabbling ducks during autumn and winter suggests that the food-preference paradigm found in waterfowl management literature is not supported by empirical evidence and that managers must continue to use best judgment in managing foraging habitats for waterfowl. Researchers and conservation planners should aim to reduce uncertainty regarding the value of waterfowl foods by conducting contemporary food-selection studies using unbiased collection and processing methodologies. Further, we suggest future researchers conduct concurrent behavioral observations, habitat use, and food selection studies within winter home ranges of dabbling ducks to aid managers in meeting the nutritional requirements of dabbling ducks during autumn and winter in North America.

Species richness and density of wintering ducks on wetlands reserve program easements in Mississippi

“…Regression analysis for active late drawdown wetlands indicated the VFQI explained ≤27% of the variation in dabbling and diving duck densities. Thus, we present several hypotheses for the lack of strong relationship between duck densities and our index of duck foods (i.e., VFQI): 1) the October‐determined VFQI did not adequately approximate quality, quantity, and seasonal dynamics in waterfowl foods at the time of surveys (Hagy and Kaminski b ); 2) selection of wetlands by ducks was influenced by metrics other than quality and quantity of food (Brasher et al , 2010, Callicutt et al ); 3) increased precipitation in winter 2008–2009 and presumed increase in regional wetland availability may have reduced the influence of food on selection of wetland by ducks; 4) invertebrate foods produced on areas with greater flood duration (i.e., active late drawdown and passive) may have influenced use by ducks (Foth ); 5) ducks used wetlands with greater VFQI values nocturnally and left at dawn to avoid hunting hours (St. James et al 2013); or 6) a combination of these or other influences. We suggest that additional investigations into factors (e.g., disturbance, weather, water depth, adjacent habitat complexes, seasonal physiological needs of ducks) influencing use of wetlands by waterfowl are needed in the Mississippi Alluvial Valley and elsewhere that ducks winter (Schummer et al , , Hagy and Kaminski b , St. James et al 2013, Hagy et al ).…”

Blood parasite infection linked to condition of spring-migrating Lesser Scaup (Aythya affinis)

“…1). Apparently healthy scaup that were observed (i.e., via spotting scope or binoculars) foraging were experimentally collected using a shotgun and sneak boat, without the aid of decoys or bait (Callicutt et al 2011). Blood was collected immediately after collection by cardiac puncture, placed into a 1.5 ml microcentrifuge tube treated with EDTA and centrifuged for 10 minutes (1500 rpm).…”

Winter waterbird and food dynamics in autumn‐managed moist‐soil wetlands in the Mississippi Alluvial Valley

“…Additionally, we included in analyses only seed and tuber taxa reported as potential food of dabbling ducks (Hagy and Kaminski 2012) and adjusted seed mass using seed size‐class correction factors to account for negative bias associated with laboratory processing of core samples (Hagy et al 2011 b ). We included all invertebrate taxa in invertebrate analyses because little information exists to characterize waterfowl diets in the MAV (Callicutt et al 2011). For all samples, we extrapolated mass estimates to kg/ha, averaged subsamples within each treatment, and calculated means and variances across sites.…”