AN ANALYSIS OF EASTERN NEARCTIC WOODPECKER DRUMS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Robert D. Stark, M.S. ***** The Ohio State University 2002 Approved by Dissertation Committee Professor David Stetson, Advisor Advisor Professor WM Mitch Masters Evolution, Ecology, and Organismal Professor Richard Bradley Biology Graduate Program UMI Number: 3062652 Copyright 2003 by Stark, Robert Douglas All rights reserved. ________________________________________________________ UMI Microform 3062652 Copyright 2003 ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ____________________________________________________________ ProQuest Information and Learning Company 300 North Zeeb Road PO Box 1346 Ann Arbor, MI 48106-1346 ABSTRACT The drum of eastern Nearctic woodpecker species was analyzed to test whether this long- distance signal was species-specific. Woodpecker drums are a series of rapid strikes with the bird’s bill on a resonant surface, not associated with foraging or cavity excavation, and has been implicated in a variety of territorial and reproductive behaviors. Previous research on drums indicated that western Nearctic woodpeckers were syntopically species-specific, with the cadence of the drum (strikes-sec-1) as the primary variable for species discrimination and recognition. However, analysis of eastern Nearctic woodpeckers indicated that species recognition by drum to be more contentious. Analysis of drums for this study included representative signals from all North American woodpecker species, except Lewis’ woodpecker (Melanerpes lewisi), currently recognized by the American Ornithologist’s Union. Drums were digitized and analyzed for the following variables: cadence (strikes- sec-1), duration (sec), number of strikes (individual strikes with a bill on a substrate during one drum), interstrike interval (sec), the duration of a single strike (sec), and the fundamental frequency of the drum (Hz). I used multivariate analysis of variance tests and a discriminant analysis function to reclassify individuals by drum for both syntopic and allotopic species. Results indicated that drums were distinctive but not species-specific, and all drum variables. ii Separating syntopic species by biome decreased misclassification when analyzed by a discriminant function. This was the same pattern as observed in western populations. Significant misclassifications occurred between Northern flickers and syntopics in all biomes. Next, using discriminant functions analyses and Mantel tests, I tested whether drums of widely distributed species indicated any geographic variation in drum parameters. Results indicated no variation in drums correlated or classifiable to region, with the exception of the black-backed woodpecker which had variation in their cadence, interstrike interval, and frequency (Hz) attributable to geographic region. Thus, the majority of Nearctic woodpeckers are acoustically uniform across ranges for drums. I tested whether phylogeny or morphological phenology (i.e., primarily feather topology) influenced the current structure of woodpecker drums. This tested whether the structure of drums could be attributable to phylogenetic influences or factors that affect species recognition between heterospecifics. I tested whether there were significant correlations between the drums cadence, duration, interstrike interval, and first principal component score versus phenotypic and phylogenic relationships. Results indicated significant correlations in both phenology and phylogeny versus selected drum variables, when all species were analyzed concurrently. Therefore, I deconstructed the dendrograms by sympatric species for six Nearctic biomes, to test whether drum divergence was significantly correlated to either syntopic phylogenic or phenotypic heterospecific influences. Results indicated some significant correlations in phylogeny and phenology when categorized by biome. Further testing indicated that the overall phylogenic significance in woodpeckers versus drum variables were due to differences at the genus, not species, level. iii Next, I recorded and analyzed the drums of four species of woodpeckers (minimum of 10 drums individual-1) to ascertain whether markers for individual recognition are encoded within the drum of each species. This analysis indicated that markers for individual recognition were encoded in the spacing of strikes within one drum and drum duration, but not within the number of strikes or the cadence within one drum. Further analysis using a discriminant function indicated that the selected drum variables encoded species, but not individual, information for all species. With the completion of the signal analysis, I used playbacks to test whether the patterns revealed from the signal analysis were recognized and pertinent to the woodpeckers in a complex acoustic environment. I recorded the responses of nine eastern woodpecker species to reciprocal playbacks of conspecifics versus syntopic and allotopic heterospecific woodpecker drums. Results indicated those species with divergent cadences in their drums were able to accurately discriminate heterospecifics versus conspecifics. However, eastern species with similar cadences were equally responsive to heterospecifics versus conspecifics while syntopic, in contrast to western species. Furthermore, allotopic red-naped (Sphyrapicus nuchalis) and yellow-bellied (S. varius) sapsuckers were found to have similar behavioral responses to reciprocal playbacks. Thus, behavioral responses to playbacks indicated that woodpecker drums were not species-specific. Nuttall’s (Picoides nuttallii) and white-headed woodpeckers (P. albolarvatus), which are normally allotopic species, are known to have one region of syntopy in the San Gabriel Mountains, San Bernardino Co., CA. Previous research (Stark et al. 1998) indicated that these species, in allotopy, had drums that were similar in cadence, duration, interstrike iv interval, and number of strikes. Analysis indicated no significant differences between species’ drums at this syntopic interface. Results from reciprocal playbacks indicated that neither species could accurately differentiate heterospecific from conspecific drums in syntopy. Reclassification by logistic regression indicated moderate interspecific differentiation by drum. Thus, these two species had not differentiated their drums in syntopy, contrary to theoretical predictions for coexistence of related species. Thus, drums may not be used for species recognition within this population. Finally, I tested the variables responsible for species recognition through behavioral analysis of black-backed woodpeckers (Picoides arcticus) to five experimentally altered signals versus unmodified conspecific drums. Results indicated that drum cadence and signal duration were important variables for discrimination of black-backed woodpecker drums from those of heterospecifics; standard downy woodpecker (P. pubescens) drums elicited signal differentiation, but artificially doubling drum duration erased clear discrimination. Modification of conspecific drums had mixed results; further analysis indicated that a combination of drum parameters may be important for species recognition. Of the competing hypotheses concerning signal discrimination in birds (i.e. invariant- features, releaser, sound-environment, alerting-message, additive-redundant, and syntactical), results indicated support for the additive-redundant hypothesis for drums, similar to that observed for song in passerines. v I wish to dedicate this dissertation to my Parents, Sharon and Robert, my brothers Brent and David, and my sister Alicia. Also, I dedicate this dissertation to my wife Danielle, whose inspiration and support made all of this possible. vi ACKNOWLEDGMENTS This research could not have been completed without the cooperation of numerous scientists and resource managers, along with private, local, state and federal agencies. I thank D. Stetson, WM. Masters, T. Waite, P. Parker, R. Bradley, D. Nelson, S. Gaunt and the Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, along with the Marjorie Osborn Fellowship for partial funding and support of this research. I further thank the Borror Laboratory of Bioacoustics, Museum of Biological Diversity, The Ohio State University for access to equipment and use of computer facilities. For research on recording and playbacks of eastern woodpecker drums, geographic variation, and phylogeny and phenologies influence on woodpecker drums, I thank J. Jackson and the Biological Sciences Department, Mississippi State University, D. Richard and the USFWS staff at Noxubee NWR, J. H. Carter III and K. Brust, along with M. Nau at the Walthour Moss Foundation, NC, B. Parsons and the North Carolina Wildlife Resource Commission, J. Walters, Virginia Tech University, T. Engstrom, Tall Timbers Research Station, E. H. Burtt, Ohio Wesleyan University, and W. Barnard, Norwich University, along with the biological research station at Algonquin provincial park, and the University of Toronto. Thanks to E. H. Miller for critical evaluation and improvement of this manuscript. Special thanks to D. Strickland and the Ontario vii provincial parks system for support of research in Algonquin. Also, special thanks to T. Shisler, Wahkeena