COOPER ORNITHOLOGICAL CLUB PACIFIC COAST AVIFAUNA Number 25 The Natural History of Magpies BY JEAN M. LINSDALE Contribution from the University of California Museum of Vertebrate Zoology BERKELEY, CALIFORNIA Published by the Club August 24, 1937 COOPER ORNITHOLOGICAL CLUB PACIFIC COAST AVIFAUNA Number 25 The Natural History of Magpies BY JEAN M. LINSDALE Contribution from the University of California Museum of Vertebrate Zoology BERKELEY, CALIFORNIA Published by the Club August 24, 1937 Black-billed Yellow-billed Magpie Magpie EDITED BY JOSEPH GRINNELL JEAN M. LINSDALE AN” ALDEN 11. hlILLRR NOTE The publications of the Cooper Ornithological Club consist of two series- The Condor, which is the bi-monthly official organ, and the Pacific Coast Avifauna, for the accommodation of papers whose length prohibits their appearance in The Condor. The present publication is the twenty-fifth in the Avifauna series. For information as to either of the above series,address the Club’s BusinessManager, W. LEE CHAMBERS,2068 Escarpa Drive, Los Angeles, California. CONTENTS PAGE Black-billed magpie; yellow-billed magpie . frontispiece Introduction . 5 Taxonomy of Pica . 8 Relation of the group to other birds; fossil records of magpies; species and races. Distribution . 14 Occurrence of the yellow-billed magpie; status of the black-billed magpie in the United States; climate and magpies. Habitat relations . .* . 35 Food and feeding habits . 48 Migration . 57 Nesting territory and courtship . 61 The nest . 76 Position; materials and composition; manner of construction; false nests; time occupied in building; repairing. Eggs and incubation . 98 Color of eggs; size of eggs; egg weight; number of eggs in set and time of laying; length of incubation period; sex performing incubation; activities of magpies during the incubation period. Young . 115 Behavior and development of young; number of broods of young; nest and egg replacement; mortality of young. Anatomy . 125 Weight; temperature. Plumages and molting . 132 Sequence of plumages; abnormal plumages and freaks of structure. General habits . 140 Perching and locomotion; roosting; bathing; voice; flocking; daily activity; miscellaneous responses. Populations , . 160 Longevity. Relations to other animals . 164 Association with other birds; relation to large mammals; invertebrate para- sites; use of nests by other animals; feeding upon other birds; bird parasites; predators. Relations to man . , . 185 Beneficial effects of man on magpies; detrimental effect of man on magpies; beneficial effect on human interests; damage to human interests; place in folklore; vernacular names of magpies. Summary and conclusion . 204 Literature cited . 208 Index. 232 INTKODUCTION The magpies are peculiarly suitable for an intensive study because they comprise a group which possessesmany distinctive features of behavior and of structure. Many races have developed, and ‘these inhabit extensive areas in the northern hemisphere. Since the magpie, wherever it occurs, prefers to live close to man, and since it is of large size, for a passerine species, a great many detailed facts have been observed in its natural history. Much of this information has been published, but it is available only in scattered places and in several different languages. No previous attempt has been made to gather together and summarize this information. In central California, I have had opportunity over a period of several years to make first-hand observations in the field upon the well-marked yellow-billed form, Pica nuttallii, and to study it in practically its entire range. An opportunity has also been afforded me to make field studies on the black-billed race, Pica pica hudsonia, in various localities in its range in the western United States. Availability of both these birds for natural history study has been excellent. Natural history studies as applied to birds have many phases, and any person who undertakes them may have many aims or only one. Often the aim is merely the satisfaction of a natural curiosity or, possibly, a well-marked collector’s instinct. Far too much work with birds has been only imitative or emulative. We make elaborate migration charts and locality lists primarily because other persons have done the same sort of thing. One of the principal objectives in the present undertaking has been to assemble a picture, as complete as possible, of the life of the magpie as an avian type. Few kinds of birds, possibly none, have been observed so often or under such widely different conditions of habitat. In spite of the many observations that have been made and published concerning the magpie, this bird is actually almost unknown to present-day ornithologists, especially in America. The factor of most weight in selecting the magpie for intensive study was the promise of opportunity to correlate general habits with structure and to contrast differing habits with structural differences of the geographic forms. It seems especially worth while to pay attention to relationships between the two American forms as they are revealed in structure and in contrasting behavior. Concentrated attention to a few closely-related forms may lead to an improved understanding of principles of biology of birds in general. This viewpoint merits more attention than it has been given in most recent natural-history monographs. In other words the aim is not alone to give a resume of all that is known about magpies, but in addition it is to see if this information answers any of the broader questions in avian distribution, migration, food relationships, and sociology. A great many printed facts relating to magpies are contained in fauna1 lists of birds. The custom of publishing all sorts of miscellaneous information on natural history in an annotated list is nearly universal among field naturalists. Reading the resulting papers gives the impression that the writers expect the facts which they present to have considerable importance for general biology. However, there is seldom any definite expression as to just how it is expected this information will be used by future workers. Is there sufficient value in this type of fauna1 paper to warrant its publication? In the present undertaking it seems desirable to keep this question in mind when going over the many fauna1 reports with the hope of making a definite judgment as to their merit. Suggestionswill be made as to what sorts of facts are most desirable in these reports. c51 6 PACIEIC’ COAST AVIFAUNA No. 25 A necessary requisite for an advance in the biology of birds is the discovery of’ additional methods of observation or of recording the results of watching. A favorable occasion for testing the usual pr’actices of field work and of widening their scope is in an application of them to some one kind of bird. One product of such a study might be suggestion of new types of procedure in field observation or in handling its results. In this study particular effort has been expended to evaluate the many phases of the life history of the magpie and the factors concerned in them, to pick out the more critical of these, and to emphasize them. In this, procedure details are given because of conviction that they have more value and greater significance than would abridged and too concise statements of conclusions. If the latter proved to be unsound, then the usefulness of the whole work would be lost. Then, too, if the details are clearly and coherently stated, it seems that the proper conclusions will follow naturally, but the converse is not true. Precaution is taken to avoid the danger of sacrificing detail of circumstances sur- rounding an observation in the attempt to improve readability. We have not reached a stage where the place of each item in the whole life story can be determined. Items which formerly were considered inconsequential have come to have significance because of certain discoveries in the physiology of birds. Therefore, it seemsbest to give refer- ences fully and to give details of some observations at the risk of making duller reading than might result from some other plan. Another problem which demands consideration is the relative dependence to be put on quantitative and qualitative observations. It may be true that an ultimate aim may be the expression of the processesof natural history in quantitative form, but it ’ also seems evident that such expression must rest on sound qualitative analysis. Little good can come from merely accumulating facts expressible in quantitative form because they are available, unless some value can be anticipated for them in inter- preting the general problems of the life cycle of the animal. Materials drawn upon for the present study belong to the following general classes, here listed in the order of my dependence upon them. (1) First-hand observations upon magpies in the field; (2) published notes on the genu’s Pica; (3) museum speci- mens, including skins, skeletons, eggs, and specimens in alcohol; (4) observations on captive birds. Throughout the main report, a comparative form of presentation is followed. Under each major topic, the form mttallii is treated first because my observations dealt with it more completely than with any other form. Next, as indicated by side-heads, the form hudsonia is considered, followed then by discussions of other kinds. This pro- cedure seems decidedly preferable to the practice, sometimes followed, of taking up closely related races in such a manner that each account is a unit. My aim is to develop a single story of the magpie, with comparisons emphasized in their natural ’ order. This volume may in one sense be considered a centennial summary of our know- ledge of the yellow-billed magpie and its near relatives. That bird was first formally described and named by Audubon a hundred years ago, from specimens obtained near Santa Barbara, California, by Thomas Nuttall, and ever since then it has attracted special interest from naturalists.