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TRANSACTIONS

OF THE

LINNAEAN SOCIETY

Studies in the

Life History of the Song Sparrow II

The Behavior of the Song Sparrow and Other Passerines

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By Margaret Morse Nice New York

September 1943

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TRANSACTIONS

OF THE

LINNAEAN SOCIETY

OF

NEW YORK

Volume VI

Studies in the

Life History of the Song Sparrow II

The Behavior of the Song Sparrow and Other Passerines

ffi

By Margaret Morse Nice

New York

September 1943

To my Husband

Table of Contents

Pa»««

FOREWORD --------------- 1

% Chapter I

BIRD BEHAVIOR --------- 4

A. The Observations of Others.

B. The Status of Birds in Comparison with Other Animals.

C. Innate and Learned Behavior.

D. Releasers, Signals, and the “Companion”.

E. Summary.

Chapter II

DEVELOPMENT OF THE YOUNG SONG SPARROW ----- 12

A. The Subjects of Study Table I.

B. The Five Stages of Development.

C. The First Stage: Coordinations Mainly Concerned with Nutrition.

D. The Second Stage: First Appearance of New Motor Coordinations.

E. The Third Stage : Rapid Acquisition of Motor Coordinations :

1. Seven Days.

2. Eight Days.

3. Nine Days.

F. The Fourth Stage: The First Week Out of the Nest:

1. Leaving the Nest Table II.

2. Feeding Reactions :

a. Behavior toward the parent-companion.

b. Independent feeding reactions.

3. Flight.

4. Bathing Reactions.

5. Escape Reactions.

6. Vocalizations.

G. The Fifth Stage: From Flight to Independence:

1. Feeding Reactions:

a. Behavior toward the parent-companion.

b. Independent feeding reactions.

2. Bathing Reactions.

3. Sunning.

4. Frolicking.

5. Escape Reactions.

6. Social Behavior.

7. Vocalizations.

H. Summary Table III.

Chapter III

DISCUSSION OF THE ACTIVITIES OF THE YOUNG BIRD - - 35

A. Activities Concerned with Nutrition :

1. Behavior toward the Parent-companion:

a. Gaping, b. Wing fluttering, c. Bowing, d. Food notes.

2. Independent Feeding Reactions.

a. Wiping the bill. b. Exploratory pecking, c. Picking up food. d. Preying reactions, e. Drinking, f. Re- action to seeds, g. Scratching the ground.

3. Defecation.

B. Care of Plumage and Other Bodily Movements in Situ, Not Concerned with Nutrition:

11

1. Preening.

2. Yawning.

3. Stretching.

4. Scratching the Head.

5. Shaking.

6. Sleeping in the Adult Position.

7. Tail and Crest Movements.

8. Bathing Reactions,

9. Sunning.

C. Locomotion :

1. In the Nest.

2. Leaving the Nest.

3. Hopping, Walking, Running.

4. Flight :

a. Wing fanning, b. Flight, c. Landing.

5. Frolicking.

D. Escape Reactions :

1. Age at Which “Fear” Appears.

E. Social Behavior :

1. Social Bond.

2. Fighting Reactions.

F. Vocalizations :

1. Food Notes.

2. Location Notes.

3. Fear Notes.

4. Threat Note.

5. Self-assertion.

6. Song.

G. Maturation of Activities in the Young Passerine Table IV.

H. Summary.

Chapter IV

INNATE AND LEARNED BEHAVIOR IN THE YOUNG BIRD - 60

A. Instinctive Activities.

B. Conditioned Actions :

1. Responses to Food.

2. Responses to Water,

3. Orientation in Space.

4. Choice of Social- Companions.

5. Escape Reactions.

6. Song.

C. The Matter of Play.

D. Summary.

Ill

Chapter V

THE COURSE OF DEVELOPMENT IN PASSERINE BIRDS - - 69

A. The Age of Fledging and Independence in Passerines Table V.

1. Relative Size of the Newly-hatched Nestling.

B. The Five Stages of Development in Passerines.

C. Summary.

Chapter VI

THE YOUNG BIRD AFTER INDEPENDENCE ------- 75

A. The Postjuvenal Molt.

B. Fall Migration.

C. Premature Appearance of Breeding Behavior :

1. Attempted Copulation.

2. Nest Building.

3. Caring for Young.

D. “Anting”.

E. Summary.

Chapter VII

SONG SPARROW SOCIETY IN FALL AND WINTER - - - - 82

A. Reactions of Song Sparrows to Other Birds Table VI.

B. Social Integration :

1. Mechanisms for Group Integration:

a. Suggestion, b. Following reactions, c. Responses to ‘warning’. d. Responses to disappearance of the social-companion, e. Social attack.

C. Social Dominance :

1. Social Dominance in the Song Sparrow.

2. Social Dominance in Other Birds and Other Animals.

D. Value of Social Integration.

E. Summary.

Chapter VIII

AWAKENING AND ROOSTING ------------- 99

A. Awakening with the Song Sparrow :

1. Twilight— Table VII.

2. Time of Arising of the Female Song Sparrow.

3. The Awakening Song Throughout the Year Tables VIII, IX.

B. Roosting with the Song Sparrow Table X.

C. Awakening and Roosting with Other Species :

1. Each Species Has Its Own “Waking Light.”

2. Awakening and Roosting in Relation to Time of Year.

3. The Situation in the Far North.

4. Awakening of Night Birds.

5. Awakening and Roosting in Relation to Sex.

D. Effect of Environmental Factors on Awakening and Roosting :

1. Light.

2. Temperature.

3. Humidity.

4. Wind.

E. Summary.

iv

Chapter IX

SONG OF THE ADULT MALE SONG SPARROW ------ 115

A. Character of the Song:

1. Form of the Song.

2. Number of Different Songs in a Repertoire.

3. The Awakening Song.

4. Flight Songs.

B. Relation of Song to Temperature.

C. How Much Does a Song Sparrow Sing?:

1. The Amount Sung at Different Stages Table XI.

2. Different Degrees of Stimulation Table XII.

3. The Song Series Table XIII.

4. The All Day Record of 4M.

5. The Different Songs of 4M and 1M Table XIV.

D. Fall Singing.

E. Summary.

Chapter X

SONG IN FEMALE BIRDS --------------- 127

A. Song of the Female Song Sparrow.

B. Discussion of Song in Female Birds :

1. The Evolution of Song in Female Birds Table XV.

2. The Function of Song in Female Birds.

C. Summary.

Chapter XI

DEVELOPMENT, INHERITANCE AND FUNCTION OF SONG - 133

A. The Five Stages of Development of Song Sparrow Song:

1. Observations on Wild Birds:

a. The progress of seven residents banded in the nest Table XVI. b. Song development in some other Song Sparrows Table XVII. c. Territory situations and song in juvenile birds.

2. Development of Song in the Hand-raised Song Sparrows Table

XVIII.

B. Inheritance of Song in the Song Sparrow:

1. Do Song Sparrows Sing Like Their Fathers and Grandfathers?

2. How Much Do Song Sparrows Imitate Each Other?

3. The Case of the Hand-raised Birds.

C. Juvenile Songs of Other Species :

1. The Age at Which Young Birds Start to Sing.

2. The Character of the Song of Young Birds.

D. Inheritance and Imitation in Other Species.

E. The Evolutionary Trend.

F. A Definition of Song.

G. Function of Song in the Song Sparrow.

H. Some Theories as to the Function of Song in Birds :

1. Early Theories.

2. Advertising Song.

3. Song as a Signal.

4. Song as an Emotional Outlet.

I. The Function of Song in Birds.

J. Summary.

Chapter XII

THE MALE AND HIS TERRITORY - - 151

A. Requirements of Territories.

B. Behavior of the Male on His Territory:

1. Defense of Territory.

2. A Summary of Song Sparrow Methods of Intimidation Table

XIX.

C. Faithfulness to Territory.

D. Relations of Song Sparrows to Other Passerines.

E. Summary.

Chapter XIII

THE FUNCTION OF TERRITORY ------- 162

A. Historical Sketch.

B. Types of Territory.

C. The Problems of Territorial and Sexual Fighting.

D. The Female and Territory.

E. The Bases and Functions of Territory.

F. Summary.

Chapter XIV

THE MALE AND HIS MATE -------------- 170

A. The Course of the Nesting Cycle Tables XX and XXI.

B. Prenuptial Stage :

1. The Cessation of Song.

2. Pouncing.

3. The Female’s Notes :

a. The Trill, b. The Chatter, c. The Song

4. Behavior of Y and D towards J and A.

C. Preliminary Stage :

1. Coition.

2. Symbolic Building.

D. Summary.

Chapter XV

RELATIONS OF THE PAIR TO EACH OTHER AND THEIR

NEIGHBORS ------------------- 180

A. The Bond Between the Pair :

1. How Permanent Is the Bond?

B. Relations of the Pair to Their Neighbors:

1. The Male and Other Males.

2. The Male and Females Not His Mate.

3. The Female and Other Females.

4. The Female and Males Not Her Mate.

C. Summary.

vi

Chapter XVI

THE PROBLEM OF PAIR FORMATION ---------- 192

A. Lorenz’s Views on Pair Formation.

B. Sexual Ambivalence.

C. The Question of Dominance.

D. Tinbergen’s First and Second Reactions Table XXII.

E. Personal Recognition of the Mate.

F. Promiscuous Tendencies in Monogamous Species.

G. Sex Recognition at Copulation.

H. Do Birds Discriminate Sex?

I. Summary.

Chapter XVII

THE NEST 209

A. Choosing the Site.

B. Building the Nest.

C. Nest Building in General :

1. Methods of Protection.

2. Nest Building.

D. The Meaning of the Nest.

E. Summary.

Chapter XVIII

THE EGGS --------- 218

A. Egg Laying.

B. Incubation :

1. The Part of the Female.

2. The Part of the Male.

3. Incubation with Other Species :

a. Share of the sexes, b. Length of periods on and off the nest Table XXIII. c. Length of incubation. d. Incubating on empty nest.

4. Role of the Non-incubating Mate.

C. Recognition of Eggs.

D. Summary.

Chapter XIX

CARE OF THE YOUNG ---------------- 228

A. Brooding.

B. Feeding the Young:

1. How Does the Male Know the Young Have Hatched?

2. The Rate of Feeding— Tables XXIV and XXV.

a. The rate per hour. b. Increase with growth of the young, c. The part played by male and female, d. Number of objects brought and number of young fed at each trip. e. Rate of feeding throughout nest life.

3. The Role of Experience.

C. Nest Sanitation.

D. Recognition of Young.

E. Helpers at the Nest.

F. Summary.

vii

Chapter XX

DEFENSE OF THE YOUNG - - - - - 245

A. Luring the Young.

B. Reaction Toward Enemies:

1. Warning Notes.

2. Deflection, Distraction Display or ‘Injury-feigning’.

3. Threat.

4. Mobbing.

5. Attack.

C. Break-up of the Family.

D. Summary.

Chapter XXI

ENEMY RECOGNITION - - --------- 255

A. Behavior of the Song Sparrow When Alarmed.

B. Reactions of Passerines to Predators :

1. The Song Sparrow and Predators:

a. Reptiles, b. Mammals, c. Birds.

2. Some Other Birds and Predators.

C. Experiments on Enemy Recognition.

D. Response of the Song Sparrow to the Cowbird.

E. Discussion of the Problem of Enemy Recognition.

F. Summary.

Chapter XXII

INNATE AND LEARNED BEHAVIOR IN THE ADULT - - - - 266

A. The Basic Needs of Animals.

B. Innate and Learned Activities in the Adult Song Sparrow Table XXVI.

C. Primitive Culture in Birds and Mammals :

1. Nutrition.

2. Protection :

a. Enemies, b. Habitat selection, c. Covey size.

3. Reproduction.

D. Instinctive Behavior Patterns throughout the Vertebrate Series.

E. Summary.

Vlll

Appendix I

CHIEF VOCALIZATIONS OF THE SONG SPARROW ----- 274

Appendix II

DOMINANCE, SINGING, AND THE CHALLENGE (PUFF-SING-

WAVE POSTURE) IN THE HAND-RAISED BIRDS - - - - 275

Appendix III

BEHAVIOR UPON THE FIRST ARRIVAL OF FEMALES - - - 280

Appendix IV

SOME SAMPLES OF COITION IN 1929 ---------- 282

Appendix V

LIST OF ORDERS AND PASSERINE FAMILIES IN WHICH DISTRACTION DISPLAY (‘INJURY-FEIGNING’) HAS BEEN REPORTED - - - ------ 248

BIBLIOGRAPHY ------------------- 285

INDEX OF SUBJECTS ---------- 172

INDEX OF SPECIES (WITH LIST OF SCIENTIFIC NAMES) - 172

LIST OF ILLUSTRATIONS

PAGE

Frontispiece. 4M Proclaims Ownership - -- -- -- -- -- -

Figure 1. Stretching, Scratching and Bathing Postures ------- 47

Figure 2. Time of Awakening Song - -- -- -- -- -- -- 103

Figure 3. Song of 1M and 4M - -- -- -- -- -- -- -- H6

Figure 4. Intimidation with the Song Sparrow - -- -- - - -- 155

Figure 5. Attitudes of the Song Sparrow in Alarm, Fear and Fright - - 255

Figure 6. Cardboard Models of Owls ------------ - 260

FOREWORD

This volume is primarily a treatise on the behavior of passerine birds with the Song Sparrow as the chief example. This species was chosen partly because it is a generalized type with no particular special- izations except perhaps in song, and also because it is the bird with which I am most familiar. From 1929 to 1936 I carried on an inten- sive study of Song Sparrows in Columbus, Ohio ; since then I have raised these birds during three summers and have studied them throughout the year in our home. This species offers many advantages as a subject for study, as pointed out in Volume I ; it is abundant, thus affording many individuals for observation; it is widely distributed (having been available to me in Ohio, Massachusetts and Michigan) ; it is easily watched, since it nests at our doorsteps and its territories are small ; it readily enters traps, and can be easily reared by hand and kept in captivity. Finally its individuality in song makes it of unique value for the study of the subject of song.

Without the technique of banding both with numbered aluminum and colored celluloid rings this research would have been impossible. Both volumes are based on intimate study of known individuals, on intensive campaigns of banding for seven years, and later on con- tinuous observation of hand-raised birds. My methods of study of the Ohio Song Sparrows are given in Volume I.

The first volume, “A Population Study of the Song Sparrow”, 1 dealt with the vital statistics of a group of Song Sparrows in Colum- bus, Ohio : their weights, migrations, territories, nesting success and failure, and the survival of adults and young. Comparisons are made with other species, but the work is chiefly concerned with a sample population of Melospiza melodia.

The emphasis in the present volume is somewhat different ; here we are dealing with passerine behavior, with the Song Sparrow as our chief illustration ; comparisons are made with many other birds, mainly, but not entirely, passerine. The book takes the bird from hatching to maturity and through its own parental activities.

Chapter II gives a detailed account of the first 4 weeks of a Song Sparrow's life, divided into 5 stages. Chapter III discusses the many activities of young passerines, arranged in 6 categories. Chapter IV is concerned with innate and learned behavior in the young bird and Chapter V with the course of develop- ment in passerines in general. Chapter VI concludes the section on the young bird with an account of behavior in the fall.

1 1937. Transactions of the Linnaean Society of NeAV York, 4:1-247.

In Chapter VII fundamental questions of social need and dominance are treated ; this is of basic importance for much of the subsequent matter. Chapter VIII on awakening and roosting leads naturally to the 3 chapters on song adult male and female, and inheritance, development and function. Territory is considered in Chapters XII and XIII, the first largely devoted to the Song Sparrow, the second to more general problems. Three chapters take up questions of mating and relations to neighbors, Chapters XIV and XV concerned mostly with Song Sparrows, Chapter XVI with problems of pair formation in general. Chapters XVII through XX on the nest, eggs, care and defense of the young, deal both with Song Sparrows and other species. Chapter XXI is on enemy recognition and XXII on innate and learned behavior in the adult. Although it was tempting to point out analogies with human behavior in many places, I refrained from doing so until the final chapter. The appendices contain detailed accounts of vocalizations, dominance, pair formation, etc., in the Song Sparrows. The gist of each chapter is given in its summary. Where quotations are made from articles or books in foreign languages, the translation is mine. Scientific names of species are given in the Index of Species.

The technique of my study was largely what Katz calls the “phenomenonological method”, i.e. description of behavior. “A nec- essary condition for success is a continuous sympathetic observation of an animal under as natural conditions as possible. To some degree one must transfer oneself into the animal’s situation and inwardly take part in its behaviour. A useful standard for determining how far one has succeeded in this is given by the certainty with which the behaviour in any concrete situation can be inwardly anticipated” (1937:49). Over 40 years ago Whitman told us we must “observe and experiment under conditions that insure free behavior (1899:302).

It is all-important to see and record exactly what a bird does. Instead of saying one bird “threatens” another, we should describe precisely the notes and gestures. We need to know a bird’s equipment of instinctive actions before we can judge as to what is innate and what is learned.

It is a pleasant duty to acknowledge help from many friends. For years I have benefited through correspondence from the advice of Dr. Wallace Craig. To the Lorenz family I am greatly indebted for their hospitality in June 1938 and to Dr. Konrad Lorenz for guidance and inspiration. Conversations with the late Dr. G. K. Noble em- phasized a different point of view. Discusssions with Dr. Tinbergen at the meeting of the Ornithologists’ Union at Washington in 1938 and with Dr. W. C. Allee and Dr. Nicholas Collias of the University of Chicago have been helpful on the theoretical points.

When I was in Austria, Dr. Lorenz and I planned to write a joint paper on “The Maturation of Some Activities in Young Redstarts and Serins”, I to furnish the observations, he the theoretical discussion and sketches. I sent him my portion which he returned with comments. Although on account of his many interests and preoccupations he never found time to write his share of the article, which consequently was never published, yet his suggestions were important and some are incorporated in Chapters III and IV.

In January 1940 the first version of the first six chapters of the present volume was sent to Dr. Craig, Dr. F. A. Beach, Jr., Mr. Daniel Lehrman and Dr. A. L. Rand for criticism; their advice was helpful not only for the revision of the chapters in question, but also for the treatment of the rest of the book. I gratefully acknowledge my indebtedness to Mr. Dean Amadon, Dr. Craig, Mr. J. J. Hickey, Dr. Ernst Mayr and my daughter Constance for their great kindness in reading and criticizing the whole manuscript.

With Joost ter Pelkwyk I discussed $nany problems and carried out with him experiments on enemy recognition. I have to thank him for the black and white sketches in this book. Thanks are also due to the National Audubon Society for the privilege of using the illus- tration by Roger T. Peterson from my article in Bird-Lore in 1936. I am much indebted to Dr. and Mrs. Miles Pirnie for their hospitality when I spent 3 weeks in 1939 at their home at the W. K. Kellogg Bird Sanctuary, Battle Creek, Michigan, raising Song Sparrows and a Cowbird. Much information on behavior of hand-raised birds has been received by letter from Mrs. Amelia Laskey of Nashville, Ten- nessee, Mr. H. R. Ivor of Erindale, Ontario, Mr. W. E. Schantz of Columbus, Ohio, and the late Mr. Ernest I. Dyer of Piedmont, Cali- fornia. As to literature, I have benefited much from the libraries of the University of Chicago. My associate editorship of Bird-Banding has brought me many books and journals which otherwise would have been difficult of access for me. I must thank my daughter Janet for help in typing this manuscript. Finally I wish to express my gratitude to my husband, Dr. Leonard Blaine Nice, for his unselfish encourage- ment of my ornithological labors during the last 23 years.

It is my hope that this book will serve as a guide to the study of bird behavior, showing, as it does, the general pattern of development and broad outlines to be expected, and giving a viewpoint and tech- nique which should help others to intensive observation and study.

4

CHAPTER I Bird Behavior

How are we to look upon birds? Are they reflex machines, or human being in miniature? Or do they fall somewhere between these extremes ? How do birds communicate with each other since they lack articulate speech? How can they carry out exceedingly complex pro- cesses, that would seem to call for foresight and planning, showing a certain amount of adaptability, yet at times fail utterly to grasp the situation when confronted with somewhat changed conditions?

In this chapter I hope to present in plain language for the bird student some of the principles of animal psychology, particularly as they relate to birds. Although the treatment is brief, an explanation is given of the terms used in the text, and references are cited to source material, books and articles, for further consultation. The point of view is fundamentally that of Lorenz, Heinroth and Tin- bergen, all of whom are more conversant with and more sympathetic with wild birds and other animals than are the laboratory psychologists. However, I have read widely on the subject of animal psychology, and have attempted to give both sides in this theoretical discussion.

A. The Observations of Others

Some investigators have combined sympathy with wild birds and other animals and wide experience with them with insight into funda- mental problems and an analytic and experimental point of view. Out- standing among these are Francis Herrick and Wallace Craig in America, Oskar Heinroth and Konrad Lorenz in Germany, Eliot Howard in England and Niko Tinbergen in the Netherlands.

Herrick was a pioneer in this country in the field of scientific watching of the breeding behavior of wild birds ; he used the blind and camera, and studied and described the chains of reflexes involved in parental care of the young and development of the latter. One of his most detailed studies was that on the development of the Black-billed Cuckoo (1910).

Craig’s works on “The Voices of Pigeons as a Means of Social Control" (1908), “Expressions of Emotion in Pigeons" (1909), “Appetites and Aversions as Constituents of Instincts" (1918), and other important papers were published in psychological journals, where they largely escaped the notice of ornithologists, whose interests, moreover, for the most part lay in other directions.

5

Oskar and Magdalena Heinroth accomplished the extraordinary feat of raising from the egg (or shortly thereafter) almost all the avian species of Central Europe ; they studied the behavior of the young birds and took a series of remark- able photographs. Their four volumes “Die Vogel Mitteleuropas” (1924-33) offer a mine of information on the development of young birds of almost all orders. Heinroth has also written many valuable articles on the vocal utterances of birds (1924), the bathing of birds (1912b, 1938b), the movements of vertebrates (1930a), etc. In “Aus dem Leben der Vogel” (1938a) he has given a brief summary of salient points in bird life, a manual of biology with birds as the text. Heinroth is director of the Berlin Aquarium ; he has had a wide experience with vertebrates the whole class of birds, and fish, amphibia and reptiles ; he is a keen observer and his conclusions are sound.

Gifted with an unusual sympathy for animals and insight into their ways, Lorenz makes use not only of his own varied and intimate experience with birds and animals, but also of Heinroth’s results, in formulating his theoretical inter- pretations of bird psychology. In his brilliant exposition "Der Kumpan in der Umwelt des Vogels” (1935) Lorenz has given us a theoretical basis for the study of bird behavior with his concept of “rel “asers” and “companions”.

Tinbergen, a careful and original investigator, co-worker with Lorenz, has published many important papers on the behavior of birds, fishes and insects, among them studies on the Northern Phalarope, Hobby, and Snow Bunting. He has also made an experimental study of gaping in young thrushes and given us several theoretical papers, particularly “The Function of Sexual Fighting in Birds” (1936a) and “On the Analysis of Social Organization among Vertebrates” (1939a).

In this country and England few studies besides those of Herrick have been made on the development of young birds. A pioneer paper by Kuhlmann (1909) appeared in a psychological journal and remained practically unknown to ornitholo- gists. The admirable study of the Ovenbird by Hann (1937) and Rand’s account of hand-raised Blue Jays (1937) and Curve-billed Thrashers (1941c) have af- forded some data on this subject.

An excellent study on gaping in Starlings was done in Switzerland (Holz- apfel 1939), while Strauss’ (1938a, 1938b) detailed studies of tame Corvidae con- tain much of value.

In England the chief interest has lain ifi matters of territory and courtship ; here Eliot Howard, Julian Huxley and David Lack have made the greatest contributions.

B. The Status of Birds in Comparison with Other Animats “Birds,” writes Huxley (1941:209) “have kept instinct as the mainstay of their behaviour,” whereas “mammals have gradually per- fected intelligence and the capacity for learning by experience”. This is evident from an examination of the brains of birds and mammals and a comparison of the size and elaboration of the cerebral hemi- spheres.

6

According to Maier and Schneirla (1935) bird behavior is “very complex. Many of its varied modes of activity have an important emotional facilitation, and vary in close relationship with visceral condition. Learning may be responsible for the extension of a specific type of activity and may make possible its elabora- tion within certain limits. However, the bounds within which learning may function appear to be established by the heritably determined factors (e. g., domin- ance of visual control, well-ordered visceral cycles, extensive development of the striate area in the brain, etc.) which themselves are responsible for the basic stereotypy pf /the activity. Therefore, while the bird is enabled to live in a very Here) to the highest degree with many inborn drives and little intelli- complex environment by virtue of mechanisms which have evolved to a high degree of elaboration, it is these possessions which are responsible for its psycho- logical limitations. It is otherwise with the mammals,” p. 263. “The behavior of lower animals depends largely upon their structural characteristics and the immediate stimulating conditions, but that of mammals is largely conditioned by previous responses. The study of mammalian psychology is therefore char- acterized by an analysis of the process of modification in behavior through experi- ence,” p. 265.

“The average bird,” writes Heinroth ( 1938a :151), “ranks well below the average mammal in its intelligence,, for with the bird, think- ing to a certain degree is replaced by flight”. Brain activity does not need to be so highly developed in the bird world, for the ability to fly enables this group of animals to solve problems in the matter of food, climate, enemies, etc., by changing their environments. As a result of her experiments on Corvidae, Hertz (1926) considered that these intelligent birds were on much the same level as monkeys in visual discrimination, behavior in mazes, and insight.

Huxley writes of birds, “They have raised emotion to the highest pitch found in animals ; the line of mammals has done the same thing for intelligence” (1941:210). “Birds are emotional animals ( Gefulhs - gence” (Heinroth 1938a). Katz tells us, “Many animals are extra- ordinarily similar to human beings in their emotional and effective life, and ... to a great extent the one essential remaining difference consists in the absence of reflectiveness in the conscious processes of animals and its presence in man” (1937 :20).

The eyesight of most birds is exceedingly keen. They have been proved to have color vision (Van Eck 1939; Warden, Jenkins and Warner 1936:195). Their hearing is acute. Experiments on its range have been carried out by Brand and Kellogg (1939), and on discrimina- tion and localization by several investigators (Warden, Jenkins and Warner 1936:179). Birds “have satisfactorily demonstrated learning

7

ability on all the usual forms of apparatus. Their records appear to be roughly comparable to those made by the sub-primate mammals in spite of the fact that the test situations have nearly always been of a kind rather better suited to the motor capacities of the latter forms” (War- den, Jenkins and Warner 1936:256). Birds have excellent memories for many things, as places and certain experiences. A Cowbird remem- bered training in relation to a problem-box as long as 11 months (Porter 1910), while a hen trained to pick up only grains of a definite color retained this training after an interval of 2 years (Claparede 1926-27). My Song Sparrow Y showed evidence of memory of ex- periments on enemy-recognition for 18 months (See Chapter XXI). Their memory for individuals, however, in many cases is surprisingly short (Chapter XVI).

C. Innate and Learned Behavior

“The basic forms of behavior in the individual are . . . dominantly hereditary in origin” (Warden, Jenkins, and Warner 1934:51). Almost all behavior is partly natively determined and partly modified by experience.

Lorenz ( 1937a :246) considers instinctive action an innate co- ordination of movement. If we restrict the term ’‘instinctive action” to this narrow sense, we will avoid the pitfalls of the vague generalities inherent in the discussion of “mother instinct”, “homing instinct”, “territorial instinct”, etc.

With this definition we can understand Lorenz’s insistence on the unmodifiability of instinctive action. Weiss’ (1941:80) experi- ments on amphibia have shown “the great rigidity and unmodifiability of coordination patterns in the lower vertebrates. . . . Thus an amphi- bian can be conditioned to exhibit a certain motor reaction, e.g., alarm, preying, retreat, etc., in response to a certain set of sensory stimuli. Yet, in producing these responses, it is bound to use the existing repetoire of preformed motor mechanisms, such as they are.”

“Each instinct involves an element of appetite, or aversion, or both,” writes Craig (1918:91), and Lorenz agrees that instinctive action is “appeted, sought or desired” ( 1937a :246).

Learning is the adjustment of behavior through experience. It plays a part in the behavior of all animals, small in some, large in others. “Learning and intelligence can decide the question, whether

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and with what intensity in an individual case a certain instinctive act will be released, but never change in the slightest the form of the finally executed movements” (Lorenz 1937b :32). Flight can go off in vacuo,, or as an unconditioned response when a Greylag first sees a Sea- Eagle, or as a conditioned response when it sees a man with a gun, or it can be used voluntarily and with insight when the bird flies over a wire fence (Lorenz 1937b :34).

The matter of threshold should not be lost sight of. Dr. Lorenz made a chart for me illustrating this for a Greylag upon the approach of a man ; there were a number of possible responses : watching the intruder, walking away, crouching, preparing to fly, flying. These different responses might depend on the nearness of the enemy, or they might illustrate the process of gradual accustoming or taming.

It often happens that the longer the interval since an instinctive action has last functioned, the lower is its threshold and the easier it is to set off. Finally a point may be reached where the action goes off without any visible stimulus, or in vacuo. On the other hand, instincts may drop out as the result of domestication, or lack of vigor in an. animal.

In many chain reflexes or “interlacing of instinct and learning” (J^riebdressurverschrankung) , variation may occur at a particular point, which usually concerns the object of the instinctive action (Lorenz 1937b:33). Thus a shrike instinctively performs the act of attempting to impale food, but has to learn that a pointed object (in nature, a thorn) is the instrument it needs.

Sometimes an instinctive action appears to improve through prac- tice. This may, however, be a matter of maturation, i.e. development. The exercising of wings by young birds is not learning to fly; it is merely premature appearance of the instinctive action. Many birds fly well with no previous practice whatever (Chapter IV). Improve- ment may also be due to facilitation, to a smoother working of the separate elements.

In his study of the sexual behavior of “Male Doves Reared in Isolation”, Craig (1914:132) writes: “When a dove performs an instinctive act for the first time, it generally shows some surprise, hesitation, bewilderment, or even fear ; and the first performance is in a mechanical, reflex style, whereas, the same act after much experience is performed with ease, skill, and intelligent adaptation. Thus even those acts which do not show improvement by the forma- tion of associations, show improvement by facilitation.”

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In most movements, besides the instinctive action, there is a spatial- ly directed component or taxis (Kuhn 1919). This has been well ex- plained by Tinbergen in respect to a shoal of fishes ( 1939a :212). A taxis is an inborn form of reaction, released by an external stimulus and directed in relation to an object. Investigations on taxes in birds have been made by Tinbergen and Kuenen (1939) in respect to gaping of nestlings, and by Lorenz and Tinbergen (1938) in regard to egg rolling by the Greylag Goose. The latest theories on taxes in inverte- brates are given by Fraenkel and Gunn (1940).

Lorenz stresses a certain kind of conditioning which he calls im- printing; it occurs early in a bird’s life and determines the objects of social reactions at maturity. He states that “most birds do not recog- nize their own species ‘instinctively’, but that by far the greater part of their reactions, whose normal object is represented by a fellow- member of the species, must be conditioned to this object during the individual life of every bird” ( 1937a :262). “This is what we might call a super-individual conditioning of the species and certainly it is the chief biological task of imprinting to establish a sort of conscious- ness of species in the young bird, if we may use the term ‘conscious- ness’ in so broad a sense” ( 1937a :265).

D. Reeeasers, Signals, and the “Companion”

Lorenz’s theory of the “companion” and “releasers” may be briefly summarized as follows :

The peculiar role that the fellow-member of the species plays in the life of the bird has been designated by Jakob von Uexkull (1934) as the “companion” ( Kumpan ). Human beings perceive objects as things, for we combine the different stimuli from the same object, but animals may react to one stimulus from an object. “An instinctive reaction of survival value, when directed to a particular object, may be released as if through a surprisingly small choice among the large number of stimuli normally emanating from the object” (Lorenz 1937a :247). When several functions have the same thing for an object, each function corresponds to a different stimulus coming from the same object. The unity of these several functions lies in the object, not in the subject.

Characters that bring definite instinctive responses in a member of the species, Lorenz calls releasers. These may be bodily organs, or striking behavior, or a combination of both ; they are compromises

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between simplicity and improbability. When a bird “releases” instinc- tive behavior in a fellow-member of the species, Lorenz calls it a “com- panion”. He lists five such parent-companion, child-companion, sex- companion, social-companion, and brother-and-sister-companion (Lor- enz 1935, 1937c).

This conception of releasers has been criticized. From various experiments on breeding European Robins Lack (1940a) concluded:

“At least in this case, the releaser concept is too simple. The general im- plications are important, for they suggest that releasers are not the fundamental units of bird behaviour. Rather, the bird reacts originally to a more general situation. At a later stage (later in evolution if the releasing complex is in- herited, later in the life of the individual if it is acquired : this issue is not dis- cussed here), the bird tends to react primarily (but not necessarily exclusively) to a characteristic part of the external situation. The characteristic part or pattern may then appear to ‘release’ the behaviour concerned: but it is not (at least always) the sole factor which will elicit the behaviour.”

Rand (1941b), citing the review by Lashley (1938) of the work of experi- mental psychologists, says, “Experiments based on varying the properties of the stimulus object point to the conclusion that the instinctive behavior is dependent on a complex of stimuli, and no investigator has found any single property of the stimulus object which cannot be varied within limits without disrupting the pattern.”

Tinbergen ( 1939a :221) discusses the releaser concept thus:

“Lorenz (1935) called all movements and structures producing a response in the social companion ' Ausloser (‘releasers’). The more general term signal is perhaps preferable since the activities and struc- tures may have releasive or directive influences, or both simultane- ously. The smell of unfertilized eggs of the Stickleback, for instance, releases the fertilizing movements of the male, although it certainly does not direct them ; orientation is optical and tactile, but not chemical. For the Lapwing, the danger call may have primarily releasive func- tion, whereas the white tail mark may have primarily directive func- tion. It is quite possible, therefore, that the concept of ‘signal’ should be subdivided into ‘releaser’ and ‘director’, although most of the signals may have both functions.”

During a discussion of this subject through letters, Joost ter Pelkwyk wrote me his definition of “signals”.

“All means by which inter-relations between animals are possible. They may be visual (color, form), auditory (notes), tactile (pecking among birds), and chemical (smell) or a combination. In general a rather complicated signal is necessary for inter-reaction. However,

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certain characters may drop out in threshold lowering. We assume that the most ‘important’ characters drop out last.

“Signals may be entirely inborn ( developing sooner or later) ; may be formed in an impressionable period (Lorenz's imprinting or Prdgung), or may be learned through conditioning. As I see it, signals are not confined to inter-relations between the individuals of one species only, but occur also between individuals of different species which influence each other in nature (predator and prey).”

(The prey “signals” to the predator by its size, movements, per- haps lack of warning coloration “something to eat” ; the predator “signals” to the prey by its form and movements “danger.”)

In my work the concept of the “companion” has proved useful,, while that of “signals” is fundamental.

E. Summary