Seed Abundance for Waterfowl in Wetlands Managed by the Illinois Department of Natural Resources

Abstract

Managed wetlands on public lands in Illinois, United States, provide foraging habitats for migrating and wintering waterfowl. However, few studies have estimated abundances of waterfowl foods in mid-migration regions of North America, yet such information is needed to inform management and conservation decision-making. During 2005-2007, we used a multistage sampling design to estimate moist-soil plant seed production (kg/ha, dry mass) and energetic carrying capacity at sites managed by the Illinois Department of Natural Resources and modeled variation in seed biomass. Average seed biomass among all sites ranged from 1,030.0 6 64.1 (SE) kg/ha in 2005 to 501.5 6 124.1 kg/ha in 2007. Our overall estimate (2005)(2006)(2007) of moist-soil plant seed biomass was precise (691.3 6 56.4 kg/ ha; CV: 8.2%), equaling 5,128 energetic use-days/ha. This value was similar to or slightly greater than previous estimates from other regions of North America and exceeded the estimate used the Upper Mississippi River and Great Lakes Region Joint Venture for waterfowl conservation planning (514 kg/ha). We formulated eight models to predict abundance of moist-soil plant seeds within sampled wetlands. The best approximating model included the number of desirable plant species within wetlands and study year. The second best model included the categorical effect of management intensity and indicated that, although variable, actively managed wetlands produced about 240 kg/ha more seed than those that were passively managed. As with other regions, wetland management practices that encourage diverse plant communities over monotypes and growth of early successional plants should yield substantial increases in waterfowl food abundances at Illinois Department of Natural Resources sites, especially given that only 27% of our study wetlands were actively managed. Such efforts would also help reduce deficits in energetic carrying capacity identified by the Upper Mississippi River and Great Lakes Region Joint Venture.

Habitat selection and activities of dabbling ducks during non‐breeding periods

“…Our estimate of plant food densities in moist‐soil wetlands in western Tennessee (633.5 kg/ha) is similar to estimates reported in the Mississippi Alluvial Valley (550 kg/ha; Kross et al ), the Upper Mississippi River Valley/Great Lakes regions (377–570 kg/ha; Brasher et al ), and the Illinois River Valley (691.3 kg/ha; Stafford et al ). Moreover, our estimate is considerably greater than was reported in palustrine emergent wetlands in the Upper Midwest during spring (208 kg/ha; Straub et al ) and in Wetland Reserve Program easements in the Mississippi Alluvial Valley during winter (263.5 kg/ha; Olmstead et al ).…”

Echoes of a flood pulse: short-term effects of record flooding of the Illinois River on floodplain lakes under ecological restoration

“…Partial river reconnection at the Merwin Preserve created high water levels during spring and early summer, followed by a progression from stagnant, warm waters to dry conditions during the post-flood summer that greatly altered vegetation conditions. Late-summer drawdowns exposed mudflats important for migrating shorebirds (Smith et al, 2012) and produced moist-soil vegetation for migrating waterfowl (Stafford et al, 2011) that also resulted in the loss of nearly all submersed and floating-leaf aquatic vegetation. Similar elimination of aquatic vegetation from fluctuating water levels during the growing season has occurred among backwater lakes and wetlands with partial connectivity to the Illinois River (Bellrose et al, 1983;Moore et al, 2010;Stafford et al, 2010).…”

Opportunity costs influence food selection and giving‐up density of dabbling ducks

“…To estimate a critical food density for comparison with GUDs, we followed the process outlined by van Gils et al () using published functional responses, daily energy requirements, and time‐activity budgets. We estimated the critical intake rate for dabbling ducks using the functional response of green‐winged teal Anas crecca (van Eerden and Munsterman ) and published estimates of energy requirements and foraging rates of dabbling ducks (Stafford et al ). We assumed 7.9–11.3 h were available to ducks for foraging based on diurnal and nocturnal foraging rates of Jones et al () and means across species of dabbling ducks from Jorde and Owen ().…”

“…We assumed 7.9–11.3 h were available to ducks for foraging based on diurnal and nocturnal foraging rates of Jones et al () and means across species of dabbling ducks from Jorde and Owen (). We used a previously estimated constant for daily energetic requirements of dabbling ducks in the Illinois River valley (337 kcal day –1 ; Stafford et al ) and mean true metabolizable energy for dabbling ducks consuming millet and rice (2.79 kcal g –1 ; Kaminski et al ). We assumed the functional response would be similar for millet and rice, given that both would have been classified as small food items by Fritz et al (), who found type I and type II function responses in mallards A. platyrhynchos were similar for small foods.…”