A Method for Quantifying Foliage-Dwelling Arthropods

Terrestrial arthropods play an important role in our environment. Quantifying arthropods in a way that allows for a precise index or estimates of density ...

Quantifying Corticolous Arthropods Using Sticky Traps

Terrestrial arthropods play an important role in our environment. Quantifying arthropods in a way that allows for a precise index or estimate of density ...

Southern Illinois University

Conservation efforts to increase duck production have led the United States Fish and Wildlife Service to restore grasslands with multi-species (3-5) mixtures of introduced cool season vegetation often termed dense nesting cover (DNC). The effectiveness of DNC to increase duck production has been variable, and maintenance of the cover type is expensive. In an effort to decrease the financial and ecological costs (increased carbon emissions from plowing and reseeding) of maintaining DNC and provide a long-term, resilient cover that will support a diversity of grassland fauna, restoration of multi-species (16-32) plantings of native plants has been explored. We investigated the vegetation characteristics, nesting density and nest survival between the 2 aforementioned cover types in the Prairie Pothole Region of North Dakota, USA from 2010-2011 to see if restored-native plantings provide similar benefits to nesting hens as DNC. We searched 14 fields (7 DNC, 271 ha; and 7 restored native, 230 ha) locating 3384 nests (1215 in restored-native vegetation and 2169 in DNC) in 2010-2011. Nest survival was similar between cover types in 2010, while DNC had greater survival than native plantings in 2011. Densities of nests adjusted for detection probability were not different between cover types in either year. We found no structural difference in vegetation between cover types in 2010; however, a difference was detected during the late sampling period in 2011 with DNC having deeper litter and taller vegetation. Our results indicate restored-native plantings are able to support similar nesting density as DNC; however, nest survival is more stable between years in DNC. It appears the annual variation in security between cover types goes undetected by hens as hens selected cover types at similar levels both years. 

Duck productivity in restored species-rich native and species-poor non-native plantings.

Indirect risk effects of predators on prey behavior can have more of an impact on prey populations than direct consumptive effects. Predation risk can elicit more vigilance behavior in prey, reducing the amount of time available for other activities, such as foraging, which could potentially reduce foraging efficiency. Understanding the conditions associated with predation risk and the specific effects predation risk have on prey behavior is important because it has direct influences on the profitability of food items found under various conditions and states of the forager. The goals of this study were to assess how ducks perceived predation risk in various habitat types and how strongly perceived risk versus energetic demand affected foraging behavior. We manipulated food abundance in different wetland types in Illinois, USA to reduce confounding between food abundance and vegetation structure. We conducted focal-animal behavioral samples on five duck species in treatment and control plots and used generalized linear mixed-effects models to compare the effects of vegetation structure versus other factors on the intensity with which ducks fed and the duration of feeding stints. Mallards fed more intensively and, along with blue-winged teal, used longer feeding stints in open habitats, consistent with the hypothesis that limited visibility was perceived to have a greater predation risk than unlimited visibility. The species temporally nearest to nesting, wood ducks, were willing to take more risks for a greater food reward, consistent with an increase in a marginal value of energy as they approached nesting. Our results indicate that some duck species value energy differently based on the surrounding vegetation structure and density. Furthermore, increases in the marginal value of energy can be more influential than perceived risk in shaping foraging behavior patterns. Based on these findings, we conclude that the value of various food items is not solely determined by energy contained in the item but by conditions in which it is found and the state of the forager.

Indirect risk effects reduce feeding efficiency of ducks during spring.

Modifications to disturbance regimes have landscape-level effects on plant communities and have the potential to influence organisms at multiple trophic levels. We examined differences in the arthropod community across a gradient of oak/hickory dominance, a plant community maintained by disturbance such as periodic fires and extensive land clearing. In southern Illinois, we used patches of forest that varied in tree dominance ranging from 94 to 0% oak/hickory composition dependent on prior land usage that occurred > 50 years ago at minimum, to test two predictions: (1) oak (Quercus) and hickory (Carya) species contain more arthropod biomass and diversity than mesic tree species [e.g., American beech (Fagus grandifolia) and maples (Acer spp.)] and (2) due to plant associations, arthropod communities are more diverse and abundant on host trees within oak/hickory stands than non-oak/hickory stands. Our results were consistent with the prediction that arthropod biomass, guild Shannon diversity, and guild richness are higher on oaks, hickories and tulip tree (Liriodendron tulipifera) than beech and maples. We also found support for the prediction that due to plant associations, % non-oak/hickory stand composition negatively influenced arthropod guild Shannon diversity and guild richness on host trees, including maples and beech. These results are the first to demonstrate that modified disturbance regimes can influence multiple trophic levels both directly due to species-specific variation in susceptibility of plants to herbivory and indirectly through effects of plant associations. This result is concerning as modified disturbance regimes are influencing large-scale plant community composition among biomes worldwide.

Linking conservation implications of modified disturbance regimes, plant communities, plant associations, and arthropod communities.

Evidence suggests that wintering populations of long-tailed ducks along the Atlantic and Pacific coasts are in decline, but little is known about wintering populations on Lake Michigan. Researchers seek answers to basic questions regarding habitat use and migration patterns (temporal and spatial) of long-tailed ducks that winter on Lake Michigan, by using surgically implanted satellite transmitters. The processes of locating the birds, capturing and implanting satellite transmitters, and interpreting the results were challenging, and efforts relied on dedicated researchers, veterinarians, resource managers, and many volunteers.

Michael W. Eichholz

Cooperative Wildlife Research Laboratory,
Center for Ecology,
Department of Zoology,
Cooperative Wildlife Research Laboratory, Center for Ecology, Department of Zoology

Southern Illinois University

A Method for Quantifying Foliage-Dwelling Arthropods

Quantifying Corticolous Arthropods Using Sticky Traps

Michael W. Eichholz

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Southern Illinois University

A Method for Quantifying Foliage-Dwelling Arthropods

Quantifying Corticolous Arthropods Using Sticky Traps

Cooperative Wildlife Research Laboratory,
Center for Ecology,
Department of Zoology,
Cooperative Wildlife Research Laboratory, Center for Ecology, Department of Zoology