Brigham Young University BYU ScholarsArchive Theses and Dissertations 1975-08-01 Habitat partitioning in a community of passerine birds Robert C. Whitmore Brigham Young University - Provo Follow this and additional works at: https://scholarsarchive.byu.edu/etd BYU ScholarsArchive Citation Whitmore, Robert C., "Habitat partitioning in a community of passerine birds" (1975). Theses and Dissertations. 7919. https://scholarsarchive.byu.edu/etd/7919 This Dissertation is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. / LL HABITATPARTITIONING IN A COMMUNITY OF PASSERINE BIRDS Publication and Manuscript in Lieu of Dissertation Presented to the Department of Zoology Brigham Young University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy by Robert C. Whitmore Jr. August 1975 'l'his publication and manuscript, by Robert C. Whitmore Jr., are accepted in their present form by the Department of .Zoology of Brigham Young University as satis­ fying the dissertation requirement for the degree of Doctor of Philosophy. • C ii ACKNOWLEDGMENTS I wish to thank several people for their help and financial assistance during the course of this study. I greatly acknowledge the guidance and assistance of Dr. Clayton M. White, my major professor and good friend, especially during this stressful last year. His companion- ship, friendship and ornithological knowledge are greatly appreciated. I thank Dr. Kimball Harper for his help and inspiration in the ecological aspects of this thesis and for many exciting conversations about theoretical and quantitative ecology. Also, I thank Dr. Joseph Murphy for his critical analysis of the manuscript, numerous favors (including funding) when he was department chairman, and his friendship. Dr. Alvin Rencher and or. Nathan Smith provided statistical consultation and computer programs for the analysis of the data. Financial assistance, which is greatly appreciated and without which this study could not have been completed was received from a D. Eldon Beck Scholarship from Brigham Young University, The Frank M. Chapman Memorial Fund of the American Museum of Natural History and the National Audubon Society. iii I would like to thank my parents for instilling a desire to learn about nature and their help in gaining an appreciation ~or the environment. Lastly, I wish to thank my wife, Leslie, for her understanding and encouragement thr?ughout this quest for an advanced degree. iv TABLE OF CONTENTS Page ACKNOWLEDGMENTS•• . iii LIST OF TABLES . vii LIST OF FIGURES. viii INTRODUCTIONTO THE DISSERTATION . 1 HABITAT ORDINATION OF PASSERINE BIRDS OF THE VIRGIN RIVER VALLEY, SOUTHWESTERNUTAH •• 3 DATA COLLECTIONAND METHODSOF ANALYSIS 4 RESULTS AND DISCUSSION . 12 SUMMARY . 23 ACKNOWLEDGMENTS . 23 LITERATURE CITED 25 HABITAT PARTITIONING IN A COMMUNITYOF PASSERINE BIRDS • . • . • . • . 28 METHODS 30 Study Area . 30 Data Collection and Method of Analysis 33 RESULTS ..... 39 Discriminant Analysis • 39 Principal Component Analysis 40 Niche Breadth and Overlap. 47 DISCUSSION . 50 SUMMARY.. 62 ACKNOWLEDGMENTS . 62 V vi Page LITERATURECITED • • • • . • • . • . • 64 APPENDIX .• • • • • • • • . • • • . • . 68 LIST OF TABLES Table Page 1. Summary of the Variables Entered by the Discriminant Function Program and Their Respective F-Values ••.••.•• 6 2. A Comparison of the James (1971) and Whitmore Ordinations on the First Discriminant Axis ........ 8 3. List of Passerine Species Encountered in the Virgin River Valley from 1 May to June 1973 Giving Symbols Used in Future Tables and Figures. • • • • . • . • . • . • . 34 4. Variables (Including Corresponding Symbols Used in Later Tables) Measured for each 0.06 Hectare Circular Plot of a Territorial Bird and Their Importance in Discriminating Between Species as Determined by the Stepwise Discriminate Function Program . • • • . • • • • • • 36 5. Correlation Matrix (r) for Ten Vegetational Variables . • • • • • • • • • • • • • • 41 6. Summary of the Results of the Principal Component Analysis of Each of 10 Vegetational Variables for 24 Species of Passerine Birds. • • • • • • • . • 43 7. Species Niche Breadth Values of the Four Most Important Variables • • • • • 48 vii LIST OF FIGURES Figure Page 1. Ordination of 24 Passerine species along the first discriminant function axis • • • • • 15 2. A two dimensional ordination using the first (I) and second (II) discriminant function axes 17 3. Study area, represented by the shaded area, located in the Virgin River Valley of southwestern Utah. • . • . • • • • . • 31 4. Two dimensional ordination of bird species along the first and second principal component axes • • • • • • • • . • • • • • 45 5. Clustering of niche overlap values obtained for each of the four most important variables . 51 viii INTRODUCTIONTO THE DISSERTATION Various techniques have been developed to aid in the quantification of avian community structure. This dissertation is composed of two papers dealing with several of those techniques; which may be looked at, simply, as different ways of analyzing the same data. In the first paper, which appeared in the Wilson Bulletin 87:65-74, Stepwise Discriminant Analysis was used to determine the habitat variables that functioned most effectively as predictors of species distributions within the ri~arian community. This multivariate statistical technique was also used to construct a two dimensional plot or ordination along known environmental gradients. The results obtained in the two phases of this study were com- pared to those of a previous study (James 1971). The second paper uses Multivariate Analysis of Variance and Principal Component Analysis to determine habitat relationships. Multivariate Analysis of Variance was used to compare species pairs and is superior to univariate tests in that it accounts for the covariate as well as the variate relationships between species. A new and different ordination was constructed using Principal Component Analysis. Finally, in this paper, two niche metrics, niche breadth and overlap, were calculated to 1 2 analyze the species relationships with themselves and each other. Together, these two papers provide an effective, but by no means complete, analysis of avian community structure. HABITAT ORDINATION OF PASSERINE BIRDS OF THE VIRGIN RIVER VALLEY, SOUTHWESTERNUTAH During the past 20 years much attention has been placed on defining habitat preferences of bird species and habitat differences between or among species. Focus has been both on closely related species groups (Sibley 1954, Dilger 1956, MacArthur 1958, Selander 1964) and entire communities (Bond 1957, Beals 1960, Cody 1968, James 1971). The theory that individual animals seek out a certain spot in the environment based on specific search images, early experience, genetic make-up or a combination of these factors is widely discussed in the literature (see Klopfer 1963, 1970). The environmental configuration of the selected sites has been termed the "niche gestalt" by James (1971). It has also been demonstrated, both theoretically and quantitatively in the field, that no two species can occupy the same niche for any prolonged·period of time (Gause 1934, Hutchinson 1959, MacArthur 1968, 1970). It is the purpose of this study to determine quantitatively the 3 4 spatial configuration of a group of passerine birds in their environment through the use of an ordination technique, to determine which habitat variables are most responsible for the separation of the species and to compare these results with those of a similar study (James 1971). DATA COLLECTION AND METHODSOF ANALYSIS Data were collected between 1 May and 30 June 1973, in the Virgin River Valley of southwestern Utah. The study area included the Santa Clara Creek from the Shivwits Indian Reservation to its junction with the Virgin River, along the Virgin River to Zion National Park and parts of Ash Creek as its junction with the Virgin River. The area is characterized by stands of dense tamarix (Tamarix pentandra), large clumps of·mature Fremont Cottonwood (Populus fremontii) and scattered patches of sand bar willow (Salix exigua). Much of the river valley is planted with alfalfa. In isolated marsh areas bull rush (Scirpus americanus), cattail (Typha sp.) and similar species may be found. I collected data in a manner similar to that of James and Shugart (1970) using a modification of the range finder circle method. Data were collected from 0.1-acre (0.04-ha) circular plots with a singing territorial male bird as the center of the circle. The biases of this type of sampling are discussed elsewhere (James 1971) and are not considered 5 important here. The variables measured for each plot are listed in Table 1. Percent canopy cover, percent ground cover and percent shrub density were all measured by taking about 20 sightings along transects from the center of the territory to its periphery, a distance of 11.3 m. Trees were divided into five 3 inch (7.62 cm) size classes and were measured directly at breast height using a graduated stick held at arms length. Tree species was also recorded. I measured canopy height using the modified Boy Scout method which uses a mirror held perpendicular to the tree, parallel to the ground. Upon approaching the tree with the hand held mirror outstretched, the point where the crown of the tree first appears