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Despite extensive anthropogenic degradation of most wetlands and other aquatic habitats associated with large rivers in the Midwest, the region still supports continentally important numbers of waterbirds during autumn and spring migration; however, few data exist to evaluate wetland restoration success and identify thresholds where changes in management may be necessary to meet conservation targets. We tracked waterbird response to restoration of a historical floodplain wetland complex along the Illinois River during 2007–2013 relative to waterbird use of other wetlands and floodplain lakes in the region. Dabbling ducks and other waterbirds showed dramatic responses to restoration, each accumulating more than 3 million use-days/year and comprising more than 30% of the total waterbird use-days in the Illinois River Valley during autumn and spring migrations. We identified use that was strongly disproportionate to availability within the region for several waterbird taxa and documented nesting by several species of conservation concern. Many species and foraging guilds of waterbirds [e.g., American coot ( Fulica americana ), dabbling ducks ( Anatini )] responded rapidly to wetland restoration, continued to use Emiquon Preserve regardless of changing conditions at reference sites, and showed relatively limited temporal variation, thereby demonstrating their utility as indicators of habitat conditions and restoration trajectory.

Populations of many shorebird species appear to be declining in North America, and food resources at stopover habitats may limit migratory bird populations. We investigated body condition of, and foraging habitat and diet selection by 4 species of shorebirds in the central Illinois River valley during fall migrations 2007 and 2008 (Killdeer [Charadrius vociferus], Least Sandpiper [Calidris minutilla], Pectoral Sandpiper [Calidris melanotos], and Lesser Yellowlegs [Tringa flavipes]). All species except Killdeer were in good to excellent condition, based on size-corrected body mass and fat scores. Shorebird diets were dominated by invertebrate taxa from Orders Diptera and Coleoptera. Additionally, Isopoda, Hemiptera, Hirudinea, Nematoda, and Cyprinodontiformes contribution to diets varied by shorebird species and year. We evaluated diet and foraging habitat selection by comparing aggregate percent dry mass of food items in shorebird diets and core samples from foraging substrates. Invertebrate abundances at shorebird collection sites and random sites were generally similar, indicating that birds did not select foraging patches within wetlands based on invertebrate abundance. Conversely, we found considerable evidence for selection of some diet items within particular foraging sites, and consistent avoidance of Oligochaeta. We suspect the diet selectivity we observed was a function of overall invertebrate biomass (51.2 ± 4.4 [SE] kg/ha; dry mass) at our study sites, which was greater than estimates reported in most other food selection studies. Diet selectivity in shorebirds may follow tenants of optimal foraging theory; that is, at low food abundances shorebirds forage opportunistically, with the likelihood of selectivity increasing as food availability increases. Nonetheless, relationships between the abundance, availability, and consumption of Oligochaetes for and by waterbirds should be the focus of future research, because estimates of foraging carrying capacity would need to be revised downward if Oligochaetes are truly avoided or unavailable for consumption.

The interaction of animals with their food can yield insights into habitat characteristics, such as perceived predation risk and relative quality. We deployed experimental foraging patches in wetlands used by migrating dabbling ducks Anas spp. in the central Illinois River Valley to estimate variation in seed removal and giving-up density (GUD; i.e. density of food remaining in patches following abandonment) with respect to seed density, seed size, seed depth in the substrate, substrate firmness, perceived predation risk, and an energetic profitability threshold (i.e. critical food density). Seed depth and the density of naturally-occurring seeds outside of experimental plots affected seed removal and GUD in experimental patches more than perceived predation risk, seed density, seed size or substrate firmness. The greatest seed removal and lowest GUDs in experimental patches occurred when food resources in alternative foraging locations outside of plots (i.e. opportunity costs) appeared to be near or below a critical food density (i.e. 119–181 kg ha–1). Giving-up densities varied substantially from a critical food density across a range of food densities in alternative foraging locations suggesting that fixed GUDs should not be used as surrogates for critical food densities in energetic carrying capacity models. Foraging and resting rates in and near experimental foraging patches did not reflect patterns of seed removal and were poor predictors of GUD and foraging habitat quality. Our results demonstrated the usefulness of GUDs as indicators of habitat quality for subsurface, benthic foragers relative to other available foraging patches and suggested that food may be limited for dabbling ducks during spring migration in some years in the midwestern USA.

Wetland restoration in highly modified landscapes involves balancing target ecosystem functions and values with constraints of landscape and stakeholder context. Often, a restored wetland complex cannot meet all target conditions simultaneously, and tradeoffs must be understood, evaluated, and quantified. We examined the tradeoff between providing migratory bird sanctuary and increasing public recreational opportunities within a restored floodplain wetland complex along the Illinois River. We surveyed the distribution and behavior of waterbirds in response to a gradient of spatial and temporal disturbances from waterbird hunting activities. Using ArcMap and spatial interpolation of waterbird densities as a novel approach to quantify sanctuary area, we estimated that approximately 42% of Emiquon Preserve functioned as sanctuary across disturbance intensities, hunter distribution, and time periods during autumn migration. Waterbird abundance did not increase with short-term temporal sanctuary or decreased hunting intensity. Disturbance distance around hunting locations was 752.1 m, overall, and increased 38.4 m for each additional hunting party. Exclusion distance around hunting locations was greater in areas with greater mean disturbance frequency. We question the effectiveness of short-term temporal sanctuary for waterbirds at the expense of recreational opportunities and advocate our analytical approach to quantify sanctuary area and disturbance buffers without experimentally causing disturbances.

More than half of the natural wetlands in the Illinois River valley (IRV) have been lost through conversion of floodplain wetlands and lakes to drainage and levee districts for agricultural production. During 2007–2013, we monitored the response of wetland vegetation communities to restoration at Emiquon Preserve, a former floodplain that was drained and farmed for more than 80 years. Spatial coverage of wetland vegetation and other cover types rapidly expanded from 252 ha in 2007 to 1,944 ha in 2013 (mean 1,512 ± 239 ha) with little supplemental planting or hydrological management. Restored vegetation emulated aquatic plant communities that were largely eliminated from the IRV, most importantly floating-leaved and submersed aquatic vegetation. Mean annual wetland cover included aquatic bed (44%), open water (20%), persistent emergent vegetation (10%), hemi-marsh (10%), and nonpersistent emergent vegetation (9%). Average moist-soil seed and tuber density was similar to managed wetlands in the IRV (mean 724 ± 224 kg/ha). A viable option for restoration of diverse aquatic macrophyte communities within degraded wetlands of large river systems includes passive restoration of hydrology and vegetation behind levees while maintaining infrastructure to facilitate drawdowns when necessary or to mimic historical conditions.

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 inter-wetland 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 = 86 F and 56 M mallards). The mean movement distance between locations collected on consecutive days was 2,822 ± 120 (SE) m (n = 1,862; max. = 56,966 m) across age, sex, and months. Female mallards (n = 35) traveled 2,708 ± 191 m during evening foraging flights (n = 145) to agricultural fields and emergent marshes. Mean home range size (95% minimum convex polygon) was 21,306 ± 1,925 ha across sex and age classes (n = 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. Overall survival was greater in 2010 (Ŝi = 0.62) than 2009 (Ŝi = 0.39) and daily survival rates were 0.8% and 0.4% greater during closed than open hunting periods in 2009 and 2010, respectively. Mallards used open water most frequently across years (49.4% daily locations), followed by corn (dryland, flooded, standing, or harvested; 16.3%), herbaceous (10.6%), woody (10.5%), and other wetlands and upland cover types. Use of areas closed to hunting was low (18.7%) and most diurnal locations of mallards occurred in wetlands open to hunting (81.3%; i.e., not designated as refuge by statute). Similar to diurnal habitat use, female mallards returning from evening foraging flights (n = 138) used areas open to hunting (81.9%) more than refuges (18.1%). Refuges that were primarily composed of open water received low use by autumn-migrating mallards in the IRV. Restoration or rehabilitation of moist-soil and emergent wetlands within statutory refuges protected from unnatural flood regimes may improve foraging habitat quality and increase survival for mallards and other ducks during migration.

Estimates of time spent at migratory stopovers are often used to develop habitat conservation objectives for a variety of avian species, namely waterfowl. Because of limited previous research and a need for accurate conservation planning objectives, we estimated stopover duration and factors influencing stay of mallards (Anasplatyrhynchos) in Illinois using radio telemetry during autumns 2009 and 2010. Total stopover duration of migrating mallards was approximately 68 days and was approximately twice that of previous studies which could have significant implications on habitat needs used for conservation planning purposes. Duration of stay post-capture did not vary by sex, body condition, year, or age but was inversely related to capture date. Our results suggest that wetland conservation objectives could increase 16.2% if our contemporary estimates were included in current planning models of the Upper Mississippi River and Great Lakes Region Joint Venture.

Understanding changes in characteristics of floodplain wetlands over time could provide valuable information to guide management and restoration efforts. We compared characteristics of 29 Illinois River valley (IRV) wetlands mapped during two time periods between 1938–1959 and 15 wetlands re-mapped in 2005–2006. Average proportions of wetlands classified as bottomland forest, scrub-shrub, nonpersistent emergent, and mud flat were generally greater during 2005–2006 than 1938–1942 or 1943–1959, but proportions of aquatic-bed and floating-leaved vegetation declined significantly by 2005–2006. We also modeled wetland use by mallards ( Anas platyrhynchos ) and diving ducks (Tribe Aythyini) during falls 1950–1959 in relation to wetland characteristics. Proportion of wetlands classified as nonpersistent emergent and an interspersion-juxtaposition index (IJI) positively associated with mallard use, whereas proportions of scrub-shrub and persistent emergent vegetation influenced diving duck use negatively. Use by both groups associated positively with wetland area and refuge. The loss of submersed and floating-leaved aquatic vegetation emphasizes the need to restore conditions that promote diverse plant communities in IRV wetlands. Composition and arrangement of wetland habitats (indicated by IJI) may be an important attractant to migrating mallards and perhaps a consideration when planning and evaluating wetland conservation efforts in mid-migration regions.

The Illinois and central Mississippi river valleys provide important habitats for migrating waterfowl. Unfortunately, both river systems have experienced large-scale hydrologic alterations, resulting in considerable loss of waterfowl habitat. To provide information to guide wetland conservation and rehabilitation efforts, we used data from aerial inventories of waterfowl conducted by the Illinois Natural History Survey to model Mallard (Anas platyrhynchos) use in relation to wetland characteristics. Mallard use was positively associated with the proportion of wetland area classified as “emergent” (e.g., containing robust or moist-soil wetland vegetation) during spring and fall in both river valleys. Use by Mallards was also related to proportion of inventoried locations where hunting and other disturbances were prohibited during fall and spring, perhaps indicating better management of fall refuges to provide foraging habitat during spring. We suggest wetland habitat acquisition and rehabilitation efforts intended to benefit waterfowl emphasize emergent-wetland components. Further, we recommend investigations of wetland use by waterfowl in each river system to elucidate the role of areas where hunting and disturbance is prohibited.

Factors that influence hunter success for waterfowl are subject to varying levels of control by managers. The relative influence of these factors is poorly understood, but such information may be valuable to guide management actions intended to promote successful hunting and communicate management decisions to constituents. We used bag-check data to investigate factors influencing hunter success for mallards Anas platyrhynchos and other dabbling ducks (tribe Anatini) during the period 1981-2000 and 2002 at Illinois public waterfowl areas. Competing models of hunter success for mallards and other dabbling ducks included a negative association with average low temperature during the duck season (uncontrollable by managers) and positive associations with estimates of local and continental duck abundance, factors which we considered partially controllable by managers. Although a certain proportion of variation in hunter success for ducks cannot be directly influenced by managers, we suggest that programs and management efforts, which promote larger continental duck populations (e.g. Conservation Reserve Program) and local duck abundance (e.g. provide quality wetland foraging habitats), may positively influence hunter success.