Suitability of Wetlands for Migrating and Breeding Waterbirds in Illinois
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APPLIED WETLAND SCIENCE
Suitability of Wetlands for Migrating and Breeding Waterbirds in Illinois Abigail G. Blake-Bradshaw 1,2,3 & Joseph D. Lancaster 2 & John R. O’Connell 4 & Jeffrey W. Matthews 1 & Michael W. Eichholz 4 & Heath M. Hagy 5 Received: 13 March 2019 / Accepted: 6 February 2020 # Society of Wetland Scientists 2020
Abstract Wetland-dependent bird populations may be limited by habitat in regions where wetland loss and degradation are pervasive, such as the midwestern United States. However, available spatial datasets, such as the National Wetlands Inventory (NWI), may overestimate habitat availability if total wetland area includes wetlands unsuitable for wetlanddependent species. During 2016–2017, we assessed proportional coverages of wetland vegetation and inundation depth typically associated with suitable waterbird habitat relative to the NWI. We also modeled these data as a function of local and landscape characteristics during spring, summer, and autumn for three guilds of wetland-dependent, migratory birds. Suitable waterbird habitat conditions based on actual wetland characteristics measured comprised a small portion of the NWI. Shallowly inundated (70% of wetlands since the 1900s, such as the midwestern United States (Tiner 1984; Dahl 1990). For instance, Illinois has lost >85% of its original 3.2 million ha of wetlands (Dahl 2006), and emergent wetlands that provide critical waterbird habitat continue to decrease (U.S. Fish & Wildlife Service 2015). Remaining wetlands are often degraded by factors including agricultural practices that alter hydrology (e.g., tiling or ditching), sedimentation, and invasive species (Tiner 1984; Zedler and Kercher 2005; Dahl 2006; Mitsch and Gosselink 2015). Degraded wetlands often provide fewer resources for wetland-dependent species, such as waterbirds (Soulliere et al. 2007; Forcey et al. 2011). Furthermore, wetland loss and degradation are likely the leading causes for population declines of some wetland-dependent bird species (Howe et al. 1989; Conway et al. 1994; Anteau and Afton 2011).
Wetlands
Despite significant losses and degradation in North America, wetlands provide essential habitat resources to support waterbirds throughout their annual cycle. Habitat resources include food, vegetation cover (e.g., thermal, escape, etc.), and hydrological characteristics required by waterbirds (Weller and Spatcher 1965; Eddleman et al. 1988; Helmers 1992). However, not all resources may be accessible to waterbirds at a given time, and thus habitat is also influenced by the ecological constraints that limit an organism’s ability to access a resource (e.g., competition, physical accessibility, etc.; Johnson 2007). Available habitat for many species of waterbirds includes vegetation that provides food and cover and often presence of surface water at the appropriate depths and hydroperiod to positively affect occupancy, abundance, or population demographics. Unfortunately, only limited information is available to monitor the quantity and suitability of wetlands fo
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