Western Michigan University ScholarWorks at WMU Master's Theses Graduate College 8-1980 An Analysis of Salt Eating in Birds Kathryn Julia Herson Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses Part of the Biology Commons Recommended Citation Herson, Kathryn Julia, "An Analysis of Salt Eating in Birds" (1980). Master's Theses. 1909. https://scholarworks.wmich.edu/masters_theses/1909 This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. AN ANALYSIS OF SALT EATING IN BIRDS by KATHRYN JULIA HERSON A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the Degree of Master of Arts Department of Biology Western Michigan University Kalamazoo, Michigan August 1880 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS I am very graceful for Che advice and help of my thesis committee which conslsced of Dr8, Richard Brewer, Janes Erickson and Michael McCarville, I am parclcularly thankful for my major professor, Dr, Richard Brewer for his extreme diligence and patience In aiding me with Che project. I am also very thankful for all the amateur ornithologists of the Kalamazoo, Michigan, area who allowed me to work on their properties. In this respect I am particularly grateful to Mrs. William McCall of Augusta, Michigan. Last of all I would like to thank all my friends who aided me by lending modes of transportation so that I could pursue the field work. These persons included Peggy Pantazopoulos Reinsch, Norman William Schafer and Terry Irving. Kathryn Julia Herson 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This was produced from a copy of a document sent to us for microfilming. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help you understand markings or notations which may appear on this reproduction. 1.The sign or “target” for pages apparently lacking from the document photographed is “Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. 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TABLE OF CONTENTS ACKNOWLEDGMENTS........................................... ii LIST OF TABLES............................................ v Chapter I. INTRODUCTION...................................... 1 II. STUDY METHODS.................................... 3 III. ANALYSIS OF HYPOTHESIS ONE: SALT EATING SERVES NO ADAPTIVE FUNCTION; BIRDS INGEST SALT ACCIDENTALLY, PERHAPS MISTAKING IT FOR GRIT.................... 5 IV. ANALYSIS OF HYPOTHESIS TWO: BIRDS EAT SALT BECAUSE OF A LACK OF IT IN THEIRNATURAL DIETS............ 10 Subhypothesis a. Salt-eating birds may live in an environment where the salt content is so low that most food obtained from the area will also be low in salt............................ 10 Subhypothesis b. At certain times of the year, birds are kept away from natural salt sources and therefore will seek out other available sources of salt (Cade 1964)...................... 12 Subhypothesis c. Salt-eating birds eat foods which have naturally low salt content, certain seeds and particularly fruits are examples (Cade 1964).... 12 V. ANALYSIS OF HYPOTHESIS THREE: BIRDS NEED AN INCREASED INTAKE OF SALT DURING CERTAIN PERIODS, FOR EXAMPLE DURING BREEDING (Schorger 1935).................... 22 VI. ANALYSIS OF HYPOTHESIS FOUR: EVOLUTIONARY CHANGES HAVE RESULTED IN HIGHER SALT REQUIREMENTS IN SOME LINES OF DESCENT (Tordoff 1964b).................. 25 VII. GENERAL DISCUSSION.............................. 31 VIII. SUMMARY........................................ 33 iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDICES................................................ 35 BIBLIOGRAPHY.............................................. 48 iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES N Salt-eating citations that emphasize that salt is not being mistaken for grit..........,.................................. 7 Observations on salt and grit ingestion at established feed­ ers in or near Kalamazoo, hichigan, January-June 1979....... 9 Number of species, number of salt-eating species, and number of expected salt-eating species per characteristic environment for the species of the orders Passeriformes, Columbiformes, and Piciformes................................................. 14 Number of species, number of salt-eating species, and number of expected salt-eating species of the orders Passeriformes, Columbiformes, and Piciformes for the coniferous forest species in comparision to all other habitats.................. 15 Number of salt-eating incidents and number of expected salt- eating incidents per season for the order Passeriformes 16 Sodium content (mg/lOOg) of some avian foods and animal matter......................................................... 17 Seasonal dietary sodium content of known salt-eating species. Diets are from Bent (1926, 1963, 1964a and b, 1965 and 1968). An asterisk (*) indicates that salt eating is well documented for the period. Y.R. indicates year-round information. The letters "V" and "I" indicate predominantly vegetarian and insectivorous diets respectively................................ 18 Number of salt-eating incidents per diet type and expected number of incidents for the salt-eating citations that included the date of the incident............................. 20 Distribution of the boreal forest species of the orders Columbiformes, Piciformes and Passeriformes. The species are classified as either salt eaters or non-salt eaters and as having characteristic diets of either low ot high salt content........................................................ 21 Number of salt-eating Incidents and expected number of salt- eating incidents for the species of the order Passeriformes in which the incidents included the date of salt ingestion. The breeding season's incidents are compared with the inci­ dents of the nonbreeding season......... ;.................... 24 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Number of species, number of salt-eating species and number of expected salt-eating species for the North American avian families................................................. vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I INTRODUCTION Salt eating in birds has not been throughly studied. There are many anecdotes of birds eating salt off winter roads, salt licks set out for deer and other animals, and natural salt licks. Cade (1964) listed some salt-eating birds and proposed that salt eating is the result of a lack of salt in the birds' diets either from foods with low sodium content or from seasonal factors such as snow cover restrict­ ing access to natural salt sources. Schorger (1935) indicated that pigeons "are fond of salt and seek it greedily, especially when raising their young." Tordoff (1954b) suggested that salt eating is taxonomi- cally restricted thus implying that genetic as well as environmental factors may be involved. Considering the connection between dietary salt and hypertension in mammals (Darrow and Yannett 1934) and known unfavorable effects of high sodium