Direct and Indirect Impacts of Emerald Ash Borer on Forest Bird Communities THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Lawrence Charles Long Graduate Program in Entomology The Ohio State University 2013 Master's Examination Committee: Dr. Daniel A. Herms, Advisor Dr. Mary M. Gardiner Dr. Kathleen S. Knight Dr. Amanda D. Rodewald i Copyrighted by Lawrence Charles Long 2013 ii Abstract Emerald Ash Borer (EAB) (Agrilus planipennis Fairmare) is an exotic invader in North American forests. The buprestid wood borer has killed millions of ash trees since its discovery in southeastern Michigan in 2002. Because North American ash trees lack an evolutionary history with EAB, it has the potential to functionally extirpate the genus Fraxinus from the North American continent. Widespread, simultaneous ash mortality is likely to initiate a cascade of direct and indirect ecological effects. Forest infestation by EAB and subsequent loss of ash trees may lead to altered habitat and food availability for native insectivores such as birds. The objectives of this research were to: (1) determine utilization of EAB as a food resource by non-migratory bark-gleaning birds, (2) quantify forest regeneration in response to EAB-induced ash tree mortality and (3) determine the impact of EAB-induced regeneration on forest bird communities. Bird/vegetation monitoring plots were established during the winters of 2011 and 2012 in 51 forested stands throughout agricultural western and central Ohio as well as along the Huron river watershed in southeastern Michigan. During the spring of 2011 and 2012, point counts were conducted at each of the three plots per site. Bird species richness, evenness and diversity were calculated for all sites based on their stage of ash tree decline as were specific indicator species. Relative abundance was calculated for common species. Following completion of spring point counts, percent cover and ii composition (ie. species, native or invasive) in the overstory, understory, shrub and herbaceous groundcover layers were assessed. Importance values were calculated for tree species. Ash trees were closely inspected for signs of EAB infestation and each was assigned a rating based upon the degree of EAB-induced decline. Observations of bark- gleaning birds were conducted at each of the 51 forests during the springs of 2011 and 2012 and the winters of 2012 and 2013. The length of time dedicated by bark-gleaning birds to each substrate type was recorded. The forested sites were situated along a gradient of EAB-induced ash decline such that Michigan sites had experienced total ash mortality greater than five years prior to study initiation, while sites in extreme southwestern Ohio remained uninfested or were in the early stages of EAB infestation. During winter months, some bark-gleaning birds showed a preference for foraging on infested ash trees. Breeding season observations revealed that some bark-gleaning birds increased the amount of time dedicated to gleaning from trees infested with EAB although no significant differences were observed. Sites that had experienced high ash mortality by the time the study was initiated had greater herbaceous groundcover, shrubby regeneration, and canopy fragmentation relative to uninfested sites or sites with low ash mortality. Sites with high ash tree mortality had more diverse bird assemblages than did forests experiencing low ash mortality. This study demonstrates how some forest birds populations can be altered due to the direct and indirect effects of an invasive insect. iii Vita 2004………………………………………..Middletown High School 2009………………………………………..B.A. Zoology, The Ohio State University 2010-present……………………………….M.S. Entomology, The Ohio State University Major Field: Entomology iv Table of Contents Abstract ............................................................................................................................... ii Vita ..................................................................................................................................... iv List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... ix Chapter 1: The Green Menace - A Literature Review ....................................................... 1 Emerald Ash Borer Biology ............................................................................................ 1 EAB Invasion of North America ..................................................................................... 2 Midwestern Ash Distribution and Ecosystem Vulnerability........................................... 3 Ecology of Invaded Forests ............................................................................................. 7 Foundational Disturbances .............................................................................................. 8 Intermediate Disturbance .............................................................................................. 13 Insect-Mediated Disturbances ....................................................................................... 13 Bark-Gleaning Bird Habits and Diet ............................................................................. 19 Impacts of Disturbance on Bird Communities .............................................................. 30 Implications of EAB Impacts on Bird Communities .................................................... 34 Research Objectives ...................................................................................................... 36 Literature Cited ............................................................................................................. 37 v Chapter 2: Direct Impacts of the Emerald Ash Borer Invasion on Bark-Gleaning Birds 51 Abstract ......................................................................................................................... 51 Introduction ................................................................................................................... 52 Methods ......................................................................................................................... 55 Results ........................................................................................................................... 63 Discussion ..................................................................................................................... 82 Literature Cited ............................................................................................................. 87 Chapter 3: Indirect Impacts of the Emerald Ash Borer Invasion: Bird Community Composition in Response to Altered Habitat Availability ............................................... 90 Abstract ......................................................................................................................... 90 Introduction ................................................................................................................... 91 Methods ......................................................................................................................... 96 Results ......................................................................................................................... 102 Discussion ................................................................................................................... 114 Literature Cited ........................................................................................................... 117 Chapter 4: Summation, Conclusions and Future Research ............................................. 122 Literature Cited ........................................................................................................... 125 Bibliography ................................................................................................................... 126 Appendix A: Importance values for tree genera in 51 study sites .................................. 140 vi Appendix B: Habitat characteristics of 51 study sites. ................................................... 142 Appendix C: Relative abundance of bird species ........................................................... 144 vii List of Tables Table 2. 1: Observed patterns in winter substrate preference for six members of the bark- gleaning guild. Post hoc Tukey’s HSD to separate means for overall model. Means are for percent time observed.................................................................................................. 76 Table 2. 2: Observed patterns in springtime substrate preference for five members of the bark-gleaning guild. Post hoc Tukey’s HSD to separate means for overall model. Means are average percent time observed. ................................................................................... 79 Table 2. 3: Relative abundances of bark-foragers based on the stage of ash decline. ...... 81 Table 3. 1: Summary statistics for MRPP of community composition compared among stages of site-level ash decline using Sorenson’s distance measure. .............................. 106 Table 3. 2: Significant indicator species (p<0.05) for sites grouped based on their average stage of ash decline. Note: some birds were indicative of different stages of decline