Michael L. Schummer

Weather-Related Indices of Autumn–Winter Dabbling Duck Abundance in Middle North America

Abstract Research on effects of key weather stimuli influencing waterfowl migration during autumn and winter is limited. We investigated relationships between changes in relative abundances of mallard (Anas platyrhynchos) and other dabbling ducks (Anas spp.) and weather variables at midlatitude locations in North America. We used waterfowl survey data from Missouri Conservation Areas and temperature and snow cover data from the Historical Climatology Network to evaluate competing models to explain changes in relative abundance of ducks in Missouri, USA, during autumn–winter, 1995–2005. We found that a cumulative weather severity index model (CumulativeWSI; calculated as mean daily temp − degrees C + no. of consecutive days with mean temp ≤0° C + snow depth + no. of consecutive days with snow cover) had the greatest weight of evidence in explaining changes in relative abundance of ducks. We concluded the CumulativeWSI reflected current and cumulative effects of ambient temperatures on energy expenditure by ducks, and snow cover and wetland icing, on food availability for ducks. The CumulativeWSI may be useful in determining potential changes in autumn–winter distributions of North American waterfowl given different climate change projections and associated changes in habitat conservation needs. Future investigations should address interactions between CumulativeWSI and landscape habitat quality, regional waterfowl populations, hunter harvest, and other anthropogenic influences to increase understanding of waterfowl migration during autumn–winter.

Twenty-First-Century Projections of Snowfall and Winter Severity across Central-Eastern North America*,+

AbstractStatistically downscaled climate projections from nine global climate models (GCMs) are used to force a snow accumulation and ablation model (SNOW-17) across the central-eastern North American Landscape Conservation Cooperatives (LCCs) to develop high-resolution projections of snowfall, snow depth, and winter severity index (WSI) by the middle and late twenty-first century. Here, projections of a cumulative WSI (CWSI) known to influence autumn–winter waterfowl migration are used to demonstrate the utility of SNOW-17 results. The application of statistically downscaled climate data and a snow model leads to a better representation of lake processes in the Great Lakes basin, topographic effects in the Appalachian Mountains, and spatial patterns of climatological snowfall, compared to the original GCMs. Annual mean snowfall is simulated to decline across the region, particularly in early winter (December–January), leading to a delay in the mean onset of the snow season. Because of a warming-induced a...

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 foo...

Effects of disturbance on activity and energy budgets of migrating waterbirds in south-central Oklahoma

We studied effects of disturbance on migrating waterbirds during spring on Cumberland Pool at Tishomingo National Wildlife Refuge, Tishomingo, Oklahoma, USA, 1999 and 2000. We recorded 240 disturbances in 477.5 hr of observation of American coots (Fulica americana), American white pelicans (Pelecanus erythrarhynchos), black terns (Chlidonias niger), blue-winged teal (Anas discors), and Franklins gulls (Larus pipixcan). Recreation (n = 208) accounted for 86.7% of all disturbances, natural disturbances (n = 23) accounted for 9.6%, and 3.3% of disturbances (n = 8) were unknown. Boat fishing increased alertness by American white pelicans but did not affect escape behavior. Recreational disturbances caused increases in escape activities and alertness of American coots. However, only boat fishing increased energy expenditure by American coots. Rates of disturbance differed between species and appeared to be correlated to foraging strategies, habitat requirements, and type of disturbance. Therefore, managers of public lands should consider habits and migration chronologies of waterbirds when setting seasonal recreation dates. Modifying recreation policy could reduce rates of disturbance to some waterbirds. Future research should be aimed at constructing energy budgets and measuring body condition of birds at multiple staging areas during spring to determine whether recreational disturbance ultimately affects reproductive success.

Dietary Overlap of Sympatric Diving Ducks During Winter on Northeastern Lake Ontario

Abstract Food resources available to diving ducks wintering on the Great Lakes have changed dramatically since the introduction of dreissenid mussels (Dreissena bugensis and D. polymorpha). We investigated the diets of Buffleheads (Bucephala albeola), Common Goldeneyes (B. clangula), and Long-tailed Ducks (Clangula hyemalis) during winter, 2002–2004, on northeastern Lake Ontario and determined the levels of dietary overlap. Dietary niche-breadth values were low, and dietary overlap values (prey size and type) were high for all species. Ducks primarily consumed high-quality, energy-dense prey (Amphipoda, Chironomidae), which were abundant. Our results highlighted three patterns: (1) dreissenid mussels constituted 85% of the macroinvertebrate community in Lake Ontario but were consumed in relatively low amounts during winter, (2) foods of high energy-density such as Amphipoda and Chironomidae were likely abundant enough for ducks to selectively feed on them, and (3) some constraint caused ducks to select energy-dense prey instead of the most available items (dreissenid mussels). Although the abundance of prey may have allowed numbers of diving ducks to increase in the past few decades on the Great Lakes, the long-term implications of high levels of dietary overlap among diving ducks is relatively unknown and warrants continued monitoring.

Projected Influences of Changes in Weather Severity on Autumn-Winter Distributions of Dabbling Ducks in the Mississippi and Atlantic Flyways during the Twenty-First Century

Projected changes in the relative abundance and timing of autumn-winter migration are assessed for seven dabbling duck species across the Mississippi and Atlantic Flyways for the mid- and late 21st century. Species-specific observed relationships are established between cumulative weather severity in autumn-winter and duck population rate of change. Dynamically downscaled projections of weather severity are developed using a high-resolution regional climate model, interactively coupled to a one-dimensional lake model to represent the Great Lakes and associated lake-effect snowfall. Based on the observed relationships and downscaled climate projections of rising air temperatures and reduced snow cover, delayed autumn-winter migration is expected for all species, with the least delays for the Northern Pintail and the greatest delays for the Mallard. Indeed, the Mallard, the most common and widespread duck in North America, may overwinter in the Great Lakes region by the late 21st century. This highlights the importance of protecting and restoring wetlands across the mid-latitudes of North America, including the Great Lakes Basin, because dabbling ducks are likely to spend more time there, which would impact existing wetlands through increased foraging pressure. Furthermore, inconsistency in the timing and intensity of the traditional autumn-winter migration of dabbling ducks in the Mississippi and Atlantic Flyways could have social and economic consequences to communities to the south, where hunting and birdwatching would be affected.

Variation in Body Composition and Digestive Organs of Tundra Swans during Migration at Long Point, Lake Erie, Ontario

Abstract. Tundra Swans (Cygnus columbianus) spend a substantial portion of their annual cycle at migratory staging areas. Despite the potential importance of staging areas to conservation of Eastern Population (EP) Tundra Swans, few data are available to assess life-history strategies of the species during migration. During 1999 and 2000, 48 adult Tundra Swans were collected during peak periods of spring and autumn migration at Long Point, Ontario, Canada, to establish baselines on nutrient reserve levels and morphology of digestive organs. Results were compared to nutrient reserve data for EP Tundra Swans collected at a major wintering area in North Carolina, USA. Lipid reserve levels did not differ between sexes nor varied with body size, but lipid reserves were approximately two times greater in autumn than spring. Males had greater protein reserves than females, and protein reserves were similar during autumn and spring. Although digestive organs were predicted to be longer and heavier during autumn, no seasonal variation in digestive organs was detected. Lipid reserve levels of Tundra Swans at Long Point during spring were similar to those recorded for wintering birds in North Carolina, suggesting that lipid reserves catabolized from autumn through winter were not replenished prior to arriving at this initial spring staging area. The results highlight the importance of managing quality aquatic and terrestrial foraging habitats at staging areas for conservation EP Tundra Swans.

Artifact Ingestion in Sea Ducks Wintering at Northeastern Lake Ontario

Abstract. The incidence of lead shot ingestion in waterfowl has declined in the lower Great Lakes (LGL) following the 1999 Canada-wide ban on use of toxic shot for waterfowl hunting, but few data exist on ingestion frequencies of spent shot or fishing weights for sea ducks wintering at the LGL. Artifact ingestion was evaluated in 269 Buffleheads (Bucephala albeola), 224 Common Goldeneyes (B. clangula) and 256 Long-tailed Ducks (Clangula hyemalis) collected at Lake Ontario during winter 2002–03 and 2003–04. Long-tailed Ducks ingested total shot (lead and steel shot combined) more frequently (6.6%) than did Common Goldeneye (1.8%) and Bufflehead (0.4%). Lead shot was ingested by Long-tailed Ducks (5.1%) and Buffleheads (0.4%), but not by Common Goldeneyes. One Long-tailed Duck, 0.1 % of all specimens, ingested one lead fishing weight. Substrate type influenced artifact ingestion frequency and diving ducks that specialize on prey associated with hard substrates may continue to ingest artifacts more than ducks using soft substrate marshes. The results suggest lead toxicosis from spent shotgun pellets is presently non-existent to low in sea ducks wintering at northeastern Lake Ontario and that further restrictions on use of lead fishing tackle may have little implication for sea ducks in this region.

Sweep-Net Sampling Acorns in Forested Wetlands

Abstract We are unaware of any previous studies to evaluate using a sweep net to estimate abundance of red oak acorns (Quercus spp.) after they fall from tree crowns, sink to the ground in flooded bottomlands (i.e., sound acorns), and become potential food for animals or propagules for seedlings. We placed known numbers of white-painted red oak acorns of 3 size classes and used a sweep net to recover them in a flooded hardwood bottomland in Noxubee National Wildlife Refuge, Mississippi, USA. We recovered large acorns 1.96 and 1.32 times more often than small and medium acorns, respectively. Mean recovery rate of all marked acorns across size and density classes was 34.0 ± 7.0% (SE, n  =  9). Thus, sweep-net sampling for sound acorns in flooded oak bottomlands may yield negatively biased estimates of acorn abundance, and investigators should consider using correction factors.

Patterns of Molt in Long-Tailed Ducks (Clangula hyemalis) during Autumn and Winter in the Great Lakes Region, Canada

Abstract. Molt and migration can coincide in Arctic nesting waterfowl because they have little time between fledging and the severe weather that precipitates migration. Objectives were to observe how patterns in autumn and winter molt by Long-tailed Ducks (Clangula hyemalis) were influenced by nutrient reserves or seasonal life-cycle events. Molt scores and nutrient reserves were determined for birds salvaged during autumn 2011 (n = 79) and collected during winter 2002–2004 (n = 255). Differences in molt among sex-age classes and correlation between molt and nutrient reserves were determined. It was predicted that adult females and juveniles of both sexes suspended molt during autumn migration to limit energetic overlap; however, greater molt in juveniles during autumn than winter was detected. Correlation between molt and nutrient reserves were not detected. Molt was less in adult males than females and juveniles during winter, which may suggest that the effects of reproduction (females) and growth (juveniles) extended their molt into winter. Observed molt patterns are consistent with fixed cues associated with the timing of seasonal life-cycle events of this species. This could have important implications in understanding the life-cycle events of Long-tailed Ducks and provide novel explanations of seasonal molt.