The Pennsylvania State University The Graduate School IMPROVED METHODS FOR MONITORING AND ESTIMATING OCCUPANCY OF NORTHERN GOSHAWKS: A FIELD TEST OF MODIFIED SURVEY METHODS A Thesis in Wildlife and Fisheries Science by Chelsea DeMarco © 2020 Chelsea DeMarco Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science August 2020 ii The thesis of Chelsea DeMarco was reviewed and approved by the following: Margaret C. Brittingham Professor of Wildlife Resources Thesis Advisor Matthew R. Marshall Adjunct Assistant Professor of Wildlife Conservation National Park Service Eastern Rivers and Mountains Network Program Manager David A.W. Miller Associate Professor of Wildlife Population Ecology Scott Stoleson Research Wildlife Biologist USDA Forest Service, Northern Research Station Special Signatory David Eissenstat Professor of Woody Plant Physiology Interim Head of the Department of the Ecosystem Science and Management iii ABSTRACT Determining status and trend of raptor populations is critical to their conservation and management, though acquiring sufficient data can be challenging and expensive, especially when species are rare or elusive. Northern goshawks (Accipiter genitilis) are a species of concern in several states, and status reviews require information on population trends and potential threats. Currently there is no cost-effective way for single states to determine goshawk population trends, especially when abundance is low. We modified two existing survey methods, the Northern Goshawk Bioregional Monitoring Design and the pre-dawn survey technique, with the goal of developing a protocol that would be more affordable and statistically relevant in areas with low goshawk abundance. First, we present modifications to and a field test of the Northern Goshawk Bioregional Monitoring Design which was developed by the U.S. Forest Service to evaluate regional trends in goshawk populations. We made 4 modifications to this design to make it affordable at smaller spatial scales and statistically relevant for areas with low abundance. We decreased the size of sampling units, stratified the sample based on known historic goshawk use instead of habitat suitability, used a conditional design to allocate survey effort and incorporated surveys conducted during the courtship and incubation breeding phases. These modifications allowed us to increase sample size, concentrate survey effort in occupied areas, detect non-breeding territorial adults, and optimize allocation of replicate survey effort, to improve detection probability and occupancy estimates. We field tested the modified method during the goshawk breeding season in 2018 to estimate detection probability and occupancy of goshawks in the iv Allegheny National Forest (ANF), Pennsylvania. Each modification contributed to the success of the method, and we estimated that goshawks occupy 6% (95% CI = 0.02-0.14) of suitable habitat in the ANF. We also found that including detections from courtship surveys was critical for the success of the method. However, current methods used to survey goshawks during courtship are logistically challenging and expensive. Second, we examine the efficacy of replacing human observers with autonomous recording units (ARUs) to overcome budgetary and logistical limitations of traditional pre-dawn surveys that are used to survey goshawks during courtship. Over 2 seasons we recorded 5040 survey hours at 91 sites in northern Pennsylvania. We built a recognizer in the program monitoR to identify goshawk vocalizations in the recordings and assessed the performance of the recognizer by evaluating precision (the proportion of identified calls that were goshawk calls), recall (the proportion of goshawk calls that were identified) and processing time. We compared results from the recognizer to results from traditional survey methods to determine the efficacy of the method. The recognizer had recall and precision rates of 72% and 67% respectively and detected goshawks in 80% (12 out of 15) of sites that were known to be occupied which was more than any other survey method. Additionally, using ARUs and the recognizer greatly reduced analysis time and survey costs. Detections from ARUs and monitoR recognizers can reduce costs and effectively identify occupied territories and vocalization patterns of elusive forest raptors as long as sufficient survey windows are used. We provide our recognizer to expedite location of goshawk calls in recordings and provide guidance for recognizer development and use in monitoR. v Modifying the Northern Goshawk Bioregional Monitoring Design and the pre- dawn survey technique enabled us to estimate occupancy of goshawks in an area with low abundance. These methods overcome limitations of previous methodologies and can be employed in other areas with low goshawk abundance allowing management entities to make conservation decisions based on local results. vi TABLE OF CONTENTS LIST OF FIGURES ..................................................................................................... viii LIST OF TABLES ....................................................................................................... x ACKNOWLEDGEMENTS ......................................................................................... xi Chapter 1 The Need for a New Methodology for Surveying Northern Goshawks .... 1 Literature Cited ..................................................................................................... 5 Chapter 2 Improving Occupancy Estimates of Northern Goshawks in Areas with Low Abundance .................................................................................................... 14 Methods ................................................................................................................ 18 Results................................................................................................................... 30 Discussion ............................................................................................................. 33 Literature Cited ..................................................................................................... 38 Chapter 3 Efficacy of Using Autonomous Recording Units to Detect Northern Goshawks .............................................................................................................. 55 Methods ................................................................................................................ 60 Results................................................................................................................... 67 Discussion ............................................................................................................. 73 Literature Cited ..................................................................................................... 80 Chapter 4 Goshawk Status and Future Surveys .......................................................... 101 Literature Cited ..................................................................................................... 108 Appendix A Example Detection Data ......................................................................... 112 Appendix B Recognizer Development and Testing .................................................... 113 Appendix C Recordings Used to Create and Test Goshawk Recognizer ................... 133 Appendix D monitoR Preparation and R Code........................................................... 135 Appendix E Template Performance ............................................................................ 163 Appendix F Detecting Goshawk Pairs Using Copulation Vocalizations.................... 180 Appendix G Goshawk Detection Data From Occupied Sites ..................................... 185 vii Appendix H Occupancy and Abundance Calculations ............................................... 187 viii LIST OF FIGURES Figure 1-1: Comparison of northern goshawk distribution between the first and second Pennsylvania Breeding Bird Atlases. ....................................................... 10 Figure 1-2: Trends in northern goshawk migration counts from 2006-2016 analyzed by the Raptor Population Index. ............................................................ 11 Figure 1-3: Status of goshawks in the eastern U.S. in 2019 according to NatureServe (2019). .............................................................................................. 12 Figure 2-1: Location of sampling units that were surveyed to estimate goshawk occupancy in the Allegheny National Forest, PA, in 2018. Upper right inset displays location of broadcast stations within the sampling units. ....................... 49 Figure 2-2: Detection probability estimates for each survey method used to estimate goshawk occupancy in the Allegheny National Forest, PA in 2018. ..... 50 Figure 3-1: Spectrograms of goshawk alarm and wail calls recorded at each 100m broadcast interval from detection distance trials conducted in February 2018 near State College, PA on an SM2 unit (Wildlife Acoustics Inc.) with 16000Hz sampling rate. Panels A, B, D and E are from alarm calls broadcast towards the ARU at distances of 100m, 200m, 300m and 400m respectively. Panel C was broadcast directly away from the unit at 200m. Panels F, G, H, are wail calls broadcast toward the ARU at 100m, 200m, and 300m. Panel I displays wail calls broadcast directly away from the ARU at 300m. ................... 90 Figure 3-2: Accumulation curve showing the cumulative proportion