Marsh birds (rallids, bitterns, and grebes) depend on emergent wetlands, and habitat loss and degradation are the primary suspected causes for population declines among many marsh bird species. We evaluated the effect of natural wetland characteristics, wetland management practices, and surrounding landscape characteristics on marsh bird occupancy in Illinois during late spring and early summer 2015-2017. We conducted call-back surveys following the North American Standardized Marsh Bird Survey Protocol three times annually at all sites (2015 n = 49, 2016 n = 57, 2017 n = 55). Across all species and groups, detection probability declined 7.1% ± 2.1 each week during the marsh bird survey period. Wetlands managed for waterfowl (ducks, geese, and swans) had greater occupancy than reference wetlands. Marsh bird occupancy increased with greater wetland complexity, intermediate levels of waterfowl management intensity, greater proportions of surface water inundation, and greater proportions of persistent emergent vegetation cover. Wetland management practices that retain surface water during the growing season, encourage perennial emergent plants (e.g., Typha sp.), and increase wetland complexity could be used to provide habitat suitable for waterfowl and marsh birds.

The Illinois River Valley (IRV) in central Illinois, USA, provides migratory stopover habitat for millions of waterfowl during autumn and spring in the Mississippi Flyway. Mallards (Anas platyrhynchos) are the most abundant species of waterfowl during autumn migration and the most harvested duck in Illinois. We investigated mallard migration ecology in central Illinois, USA, to address information needs of biologists and managers in the Upper Mississippi River and Great Lake Region Joint Venture and Illinois Department of Natural Resources. Our objectives were to document daily movements and identify factors affecting interwetland movements, investigate lengths of foraging flights, assess home range size during stopover, describe habitat use and identify factors associated with wetland use, estimate survival and cause specific mortality, and evaluate proportional use of refuges and areas open to hunting in and nearby the IRV by mallards. We employed standard radio-telemetry techniques to achieve our objectives during autumns and early winters 2009 and 2010 (n ¼ 86 F and 56 M mallards). The mean movement distance between locations collected on consecutive days was 2,822 AE 120 (SE) m (n ¼ 1,862; max. ¼ 56,966 m) across age, sex, and months. Female mallards (n ¼ 35) traveled 2,708 AE 191 m during evening foraging flights (n ¼ 145) to agricultural fields and emergent marshes. Mean home range size (95% minimum convex polygon) was 21,306 AE 1,925 ha across sex and age classes (n ¼ 81 mallards). We documented 43 mortalities of 142 radio-marked mallards (2009: 28.2%; 2010: 32.3%) with 85.0% and 69.6% of deaths attributed to hunting in 2009 and 2010, respectively. Body condition, hunting period, age, year, minimum daily temperature, and daily movement distance were important variables affecting survival, but differences were most pronounced for year and hunting period.

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Spring migration is an energetically demanding event that can impact nutrient dynamics of individuals during the breeding season through carry-over effects. Limited food availability at spring stopover areas may have cross-seasonal effects that adversely impact waterfowl populations. We collected 161 Green-winged Teal (Anas crecca Linnaeus, 1758; hereafter Teal) throughout the Illinois River Valley, USA, during February–April of 2016–2018 and estimated body condition using three condition indices (scaled mass index, scaled wing index, body-size index) for comparison with carcass lipid and protein values. Lipids were 18.3% (95% CI = 1.0%–38.5%) and 21.6% (95% CI = 4.8%–41.0%) greater at locations with moderate (250–600 kg/ha) and high (>600 kg/ha) moist-soil seed densities, respectively, than low moist-seed density (<250 kg/ha) sites. Lipids also increased 2.4% (95% CI = 0.2%–5.1%) with every 10% increase in the proportion of plant seeds in diets and decreased 0.9% (SE = 0.4%–1.4%) and 3.8% (SE = 2.1%–5.4%) with every 1-day increase in collection date and 1 °C rise in mean temperature, respectively. Condition indices based on morphology were poor (r ≤ 0.45) predictors of lipids and led to potentially erroneous conclusions regarding important contributions to body condition. Availability of emergent wetlands with adequate food resources may affect lipid reserves of Teal during spring migration and have cross-seasonal effects during the breeding season.

Although most emergent wetlands across central North America have been destroyed or degraded, wetland restoration in recent decades has provided new habitat resources for wetland birds in agriculturally dominated landscapes. The goals of wetland restorations often include providing habitat for migratory and breeding waterfowl and other wetland birds. One such restored wetland complex in the Illinois River Valley, the Emiquon Preserve, is isolated from most flooding events of the Illinois River allowing the growth of persistent emergent vegetation that was quickly colonized by breeding wetland birds. We examined nest occurrence and variables influencing site selection, nest success, and changes in nest density across stages of the wetland succession cycle. We located 327 nests from nine species of wetland birds (American Bittern, Botaurus lentiginosus; American Coot, Fulica americana; Black-crowned Night-Heron, Nycticorax nycticorax; Black-necked Stilt, Himantopus mexicanus; Common Gallinule, Gallinula galeata; Green Heron, Butorides virescens; Least Bittern, Ixobrychus exilis; Pied-billed Grebe, Podilymbus podiceps; Sora, Porzana carolina) during 2013-2019. Common Gallinules were more likely to nest in persistent emergent vegetation than other cover types. American Coots and Least Bitterns selected nest sites based on water depth. Black-necked Stilt and Black-crowned Night-Heron nests were less successful in deeper water. Black-necked Stilt, Black-crowned Night-Heron, and Common Gallinule nests were less successful with later initiation dates. Nest density did not vary between persistent emergent and hemi-marsh cover types. Across 2013-2019 we estimated an average of 372 nests/year for six marsh-nesting bird species at Emiquon, including two state-endangered (Common Gallinule and Black-crowned Night-Heron) and one state-threatened (Least Bittern). Wetlands restored from agricultural fields can quickly provide critical breeding habitat for marsh-nesting birds of conservation concern, although continued management is needed to provide resources to maintain persistent emergent vegetation communities as individual marshes transition through the marsh cycle.

Avian diet quality is typically measured using true metabolizable energy (TME N ), which is a measure of assimilable energy of food items accounting for innate endogenous losses. Originally developed for use in the poultry industry, TME N methods have been adapted to determine the value of natural foods consumed by waterfowl to parameterize bioenergetics models for conservation planning. Because there is little knowledge of the variation in TME N estimates among food items and waterfowl species, we investigated TME N of 6 common species of submersed aquatic vegetation for mallards (Anas platyrhynchos; i.e., a diet generalist) and gadwall (Mareca strepera; i.e., a diet specialist) in the midwestern United States during autumn 2015-2017. We precision fed and collected excreta from ducks using standard bioassays to estimate TME N . Mallards had slightly greater TME N than gadwall, but there was considerable variation in TME N among vegetation species, duck species, and individuals within each species. True metabolizable energy (±SE; kcal/g[dry]) for mallards was greatest for Canadian waterweed (Elodea canadensis; 1.66 ± 0.26), followed by coontail (Ceratophyllum demersum; 1.51 ± 0.28), southern naiad (Najas guadalupensis; 1.37 ± 0.39), sago pondweed (Stuckenia pectinata; 0.50 ± 0.22), wild celery (Vallisneria americana; 0.05 ± 0.42), and Eurasian watermilfoil (Myriophyllum spicatum; -0.13 ± 0.42). Mean TME N for gadwall was greatest for Eurasian watermilfoil (0.77 ± 0.32), followed by Canadian waterweed (0.70 ± 0.31), coontail (0.55 ± 0.28), southern naiad (-0.61 ± 0.34), wild celery (-0.98 ± 0.39), and sago pondweed (-1.07 ± 0.33). Generally, TME N for most vegetation species was less than agricultural grains, but it was similar to ranges reported for seeds of naturally occurring hydrophytic vegetation and aquatic macroinvertebrates. We recommend that conservation planners incorporate species-specific TME N estimates in bioenergetics models and that future researchers improve TME N assays for wild waterfowl following our recommendations.

Predator management regularly improves waterfowl nesting success, often beyond levels believed necessary for population maintenance. If recruitment, survival of breeding females, and/or breeding site fidelity is increased on predator‐reduced sites, then local breeding populations may increase in subsequent years. During 2005–2008, we annually conducted breeding pair surveys on >600 wetlands at 6 township‐sized (93.2 km2) trapped sites and 4 non‐trapped sites for the 5 most common upland nesting ducks in eastern North Dakota, USA. For each species, we developed a series of competing regression models that related breeding pair abundance to wetland size, predator management, and upland habitats adjacent to sampled wetlands. In contrast to previous studies, we found limited and equivocal evidence that breeding populations increased following predator management. We discuss multiple potential explanations for this lack of effect and suggest that managers should not assume that increased production as a product of elevated nest success will be compounded over years. © The Wildlife Society, 2013

Waterfowl use stopover sites during spring migration to rest and replenish nutrient reserves prior to their arrival on breeding grounds. Estimating the extent to which an individual remains at a stopover site before dispersing (i.e., stopover duration) is essential for managers to develop wetland habitat objectives needed to ensure sufficient resources are available to meet the needs of migrating waterfowl. Our objectives were to determine average stopover duration of dabbling ducks in the Wabash River Valley (WRV) of Illinois and Indiana, USA, identify factors that may influence that duration, and evaluate how those duration values compare with those currently used by the Upper Mississippi River and Great Lakes Region Joint Venture (UMRGLRJV). We estimated stopover duration of 39 mallard (Anas platyrhynchos) and 62 green‐winged teal (A. crecca) between January and April 2016–2017 in the WRV. Estimated stopover duration for mallards and green‐winged teal was 17.0 days (95% CI = 12.6–22.9). Our estimate is substantially shorter than current estimates used by the UMRGLRJV for conservation planning and could affect conservation objectives for waterfowl. © 2019 The Wildlife Society.