Nesting White Ibis prey use in Everglades National Park in 2017 and 2018

Prey composition of White Ibis nesting in Everglades National Park in 2017 and 2018 We quantified prey use of ibises nesting in the ecotone of Everglades National Park in 2017 and 2018 by examining the contents of regurgitated food boluses collected from nestlings. We collected boluses weekly for ~5 weeks each year during the peak provisioning period when chicks are between 12 and 28 days old. Most boluses (~90%) were collected from the ground or nesting substrates following voluntary regurgitation and the rest were collected via esophageal massage.Each bolus was picked through twice, and all useful prey parts were recorded, counted, and sorted into vials of 70% ethanol similar to methods used in previous diet studies (Boyle et al. 2014). We measured lengths of prey parts and back-calculated dry masses of fish and most invertebrates with regressions developed for previous assessments of ibis diets (Boyle et al. 2014). White Ibis nesting activity We conducted aerial surveys of nesting ibis at seven historical colonies in the ecotone of Everglades National Park from 1999 and 2018. We monitored active nesting colonies monthly from January through June using fixed-winged aircraft and helicopters flown at an altitude of 150-250 meters above ground level. During each flight, we took photos of the entire colony using a high-resolution DSLR camera and telephoto lens. We examined the photos to determine the stage of nesting and number of nests. We counted nests during the incubation stage, when the white incubating adult could be detected against the darker background of the nesting colony; we assumed each horizontally sitting (incubating) adult equated to one nest. We estimated total nest counts by rounding the number of nests up to the nearest 5, 50, or 100 nests for colonies with <100, 100-1000, and >1000 nests, respectively. We used the total nest count for each colony as a measure of colony-level nesting effort. We summed total nest counts for all colonies in the ecotone each year to examine temporal trends of total nesting effort in the coastal ecotone of Everglades National Park. Crayfish Production We quantified wet-season crayfish (Procambarus alleni and P. fallax, combined) catch rates at five spatially-fixed sampling sites in marl prairies and sloughs east of the colonies in each October preceding the 2017 and 2018 dry seasons (i.e. October 2016 and 2017). At each of the five sites we set six non-baited minnow traps (three 3.0 mm and three 6.4 mm wire mesh traps) for 22-24 hr. We considered the aggregate catch of six traps at each site a single effort. Crayfish were identified to species and measured (mm carapace length), and dry weights were calculated using length-weight regressions (Boyle et al. 2014). We compared mean crayfish catch rates (crayfish effort−1) and biomass (g dry mass effort−1) between 2016 and 2017 with paired one-tailed t-tests. Crayfish biomasses were natural log transformed to help meet assumptions of the analyses.