Depressions Provide High-Quality Wading Bird Foraging Patches in a Seasonally-Pulsed Wetland

Abstract In seasonally-pulsed wetlands, large breeding events of colonial-nesting wading birds depend on the occurrence of foraging patches rich in aquatic prey that are available throughout the breeding season. The seasonal flood pulse and subsequent water recession can elevate prey biomass and density. However, there remains a gap in our understanding of how prey species within the water column are redistributed to create localized high-quality foraging patches during the wading bird breeding season. To better understand the mechanisms that create high-quality foraging patches, we measured prey biomass and density in an experimentally manipulated wetland substrate within the Florida Everglades. We hypothesized that wading bird prey biomass and density would be higher within depressions than in the surrounding wetland. We found that wading bird prey concentrate within depressions throughout the range of water depths accessible to foraging wading birds. Prey biomass and density also peaked at substantially higher levels within depressions than in the unmanipulated marsh surface. Additionally, we found that larger prey (total length ≥ 5 cm), which are an important resource for wading birds, peaked at higher levels within depressions, than in the unmanipulated marsh surface and accounted for greater than half of the biomass in depressions. Our findings provide empirical evidence that depressions are a mechanism for creating high-quality foraging patches for wading birds. Understanding the mechanisms that provide these high-quality foraging patches fills a critical gap in our knowledge and will allow water and land managers to better conserve and restore wading bird populations in seasonally-pulsed wetlands.