Wetland Birds

Contributed Paper
ROOM: CC, Room 26A

8:10AM Factors Affecting Detection Probability and Abundance of Virginia Rail and Sora in the Lake Erie Coastal Marshes of Northern Ohio
James Hansen; Nicole Hengst; Brendan Shirkey; John Simpson; Robert Gates
Secretive marsh bird surveys using the Standardized North American Marsh Bird Monitoring Protocol are conducted across much of the upper Midwest to assess population trends of several marsh bird species. However, sampling frameworks have varied among monitoring authorities, and species-specific and sub-regional recommendations for various sampling frameworks have not been evaluated. Sora (Porzana carolina) and Virginia rails (Rallus limicola) are of interest in Ohio because of their status as game birds with liberal harvest regulations, and there are no estimates of abundance for these species in Ohio. We aim to evaluate the efficacy of contrasting sampling designs to estimate population sizes of Virginia rails and sora. Point count surveys using the National Protocol were conducted at Winous Point Marsh Conservancy in Northern Ohio in 2017, from points located on dikes and from interior points located in wetlands to compare differences in abundance associated with survey point placement (dike vs. wetland). Biotic and abiotic covariates were measured to investigate factors that affect estimates of detection probability and abundance of Virginia rails and sora. Survey data were analyzed using N-mixture models in a Bayesian framework with program Jags. Mean detection probabilities were similar between sora and Virginia rails (0.046 ± 0.025 and 0.095 ± 0.018, respectively). Percent cover and height of emergent vegetation had the greatest positive effect on estimates of abundance for both species. Detection probability was nonlinearly related to cloud cover, suggesting a possible relationship between weather variables that affect migration behavior, and potentially resulting in an open population during the survey period. There was no significant difference between estimates of detection probability from survey points located on dikes versus within wetlands. These results can be applied to inform the implementation of marsh bird monitoring surveys to track population trends and evaluate effects of management actions on local abundance.
8:30AM Marsh Bird Use of Wetlands Managed for Waterfowl in Illinois
Therin M. Bradshaw; Abigail G. Blake-Bradshaw; Heath M. Hagy; Christopher N. Jacques; Joseph D. Lancaster
It’s widely assumed that waterfowl management activities benefit other birds, but few studies have quantified those benefits or tradeoffs among management strategies for multiple species. Overall, marsh birds are an understudied guild that can be valuable indicators of wetland health. During late spring and early summer 2015-2017, we conducted call-back surveys to detect marsh bird use of wetlands and assess wetland quality using a modified version of the Ohio Rapid Assessment Method (ORAM) throughout Illinois. We selected survey locations from three types of sites, 1) focal sites with passive or active management for waterfowl, 2) random sites that were selected from emergent National Wetland Inventory polygons using a stratified random approach, 3) and Critical Trends Assessment Program (CTAP) sites that are regularly surveyed through a long term ecological survey program in Illinois. We conducted three rounds of surveys at each site. Our objectives were to 1) compare marsh bird use of restored and natural wetlands, 2) determine characteristics of wetlands and the surrounding landscape that influence marsh bird use of wetlands, and 3) compare marsh bird use of wetlands managed for waterfowl across a continuum of management intensities. Preliminary analysis suggests differences in detections across management intensities, percent flooded, and water depth. Average detections were greatest during round one surveys (x-bar = 14.5, SD= 46.3), followed by round two (x-bar = 7.5, SD= 28.6), and round three (x-bar = 2.2, SD= 5.7). Average detections were highest in focal sites (x-bar =21.7, SD= 54.7), followed by random (x-bar = 2.9, SD= 9.0), and CTAP sites (x-bar = 0.4, SD= 0.8). We used logistic regression in an occupancy modeling framework to evaluate potential effects of environmental factors on probability of detection and habitat use. Our goal is to provide management recommendations that will encourage marsh bird use and increase overall wetland quality.
8:50AM Converting Marshbird Counts to Density: Adjusting for Distance and Variable Amounts of Potential Cover at Survey Points
Nina Hill; David E. Andersen; Douglas H. Johnson; Tom Cooper
Estimates of abundance derived from point counts generally assume that the area surrounding the point has some likelihood of an animal being present. Recent assessments suggest that counts at points are a reasonable proxy for abundance, in at least some cases, although many approaches attempt to account for imperfect detection and the influence of distance from the observer on detection probability. However, in situations where only a portion of the area surrounding a point has positive probability of occupancy, count data are not a useful proxy for abundance and no clear guidelines exist for transforming counts to estimates of density. We describe a process to convert secretive marshbird counts at points to densities that accounts for variable amount of wetland cover in the area surrounding points, and detection varying with distance. Standardized protocols for surveying secretive marshbirds employ unlimited-distance point-counts, conducted from a point located near the wetland-upland transition edge, resulting in different areas of wetland surrounding individual points. We used the distribution of detection distances scaled to wetland area as a function of distance from survey points to adjust counts at points. We then used the effective survey distance to sum the amount of wetland cover actually surveyed and derive an estimate of density for each point. This approach incorporates both the difference in wetland area at each survey point and the decreasing probability of detection with distance, and allows for comparison of abundance and factors related to abundance across survey points. We suggest that a similar approach would be appropriate in other circumstances where the area surrounding survey points that could potentially support a species of interest varies among points (e.g., where area of appropriate cover types is smaller than the effective surveyed area).
9:10AM Of Woodcock and Warblers: Two Species Trying to Thrive in the Same Landscape
Henry M. Streby; Gunnar R. Kramer; Sean M. Peterson; Kyle O. Daly; David E. Andersen
Multi-species approaches to wildlife management have become commonplace. These strategies manage different species under a single regime based on shared habitat associations and/or co-occurrence on a landscape. However, managers regularly lack information about species-specific relationships between landscape composition and life history parameters (i.e., vital rates, population growth rates). Therefore, multi-species management often relies on the assumption that species with shared habitat associations will respond similarly to management of landscape components based on consideration of a single surrogate or umbrella species. We tested the efficacy of multi-species management in two migratory birds. American Woodcock (Scolopax minor) and Golden-winged Warblers (Vermivora chrysoptera) breed in diverse-forest landscapes of eastern North America and are often associated with young or early-successional forest patches. Management for each of these species is purported to benefit the other, and the two are often presented as the game and non-game flagship species for young forest initiatives. We used demographic data, collected concurrently on a landscape shared by these species in Minnesota, to create spatially-explicit models of full-season productivity (i.e., the number of juveniles raised to independence from adult care) and compare productivity between species across the landscape. We found significant negative relationships in full-season productivity between these species at all spatial scales we measured (1 m2 – 100 ha). Our results suggest that American Woodcock and Golden-winged Warblers have opposing relationships with the composition and configuration of forested landscapes, and therefore likely do not respond similarly to any individual management action at any relevant spatial scale.
9:30AM Development of an Avian Index of Biological Integrity for Kentucky Wetlands
Kaitlyn J. Kelly; David Brown
Bird communities are frequently used as bioindicators to assess environmental conditions, including in wetland habitats. I developed an avian index of biological integrity (IBI) for wetlands of Kentucky as an intensive assessment method to supplement an existing rapid assessment method used in regulatory programs. Birds are useful indicators because they are sensitive to environmental changes, abundant in various landscapes, occupy higher trophic levels, and can be sampled in a cost-effective manner. Breeding bird point count data from 103 sites were used to calculate a set of 49 avian community metrics. Avian metrics were tested for correlation with independent landscape, hydrology and habitat measures of wetland condition. High performing, non-repetitive metrics were tested using a model averaging approach to find the best set of avian community metrics that predicted an independent measure of wetland condition. Final metrics were scaled and assembled into an Avian IBI. I found four superior metrics to be significantly related to the independent disturbance index. The final metrics used to create the Avian IBI were percent presence of insectivores, percent presence of ground gleaners, percent presence of residents and Shannon Wiener Diversity Index. Both Shannon Wiener Diversity Index and percent presence of insectivores decreased with increasing disturbance. Percent presence of ground gleaners and percent presence of residents had a positive relationship to disturbance. Previous studies found similar results with insectivorous guilds being intolerant to human disturbance, whereas ground-gleaning guilds tend to be more tolerant. This cost-effective and time-efficient IBI complements existing assessment tools for wetlands of Kentucky.


Contributed Paper
Location: Cleveland CC Date: October 8, 2018 Time: 8:10 am - 9:50 am