Ecology of Passerine Birds Wintering at Utah Lake

Brigham Young University BYU ScholarsArchive

Theses and Dissertations

1951-06-01

Ecology of Passerine birds wintering at Utah Lake

Joseph R. Murphy Brigham Young University - Provo

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BYU ScholarsArchive Citation Murphy, Joseph R., "Ecology of Passerine birds wintering at Utah Lake" (1951). Theses and Dissertations. 7834. https://scholarsarchive.byu.edu/etd/7834

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ECOLOGYOF PASSERINEBIRDS WINTERINGAT UTAHLAKE

A Thesis submitted to the Department of Zoology and Entomology ot Brigham Young University

In partial fulfillment or the requirements for the degree of Master of Arts

by Joseph R. Murphy

June 19,1

..-: '" Thia thesis by Joseph a. KurphJ 11 accepted 1n its present form by the Special Thesis Committee as satlsty1n1 the thesis requirements tor the degree ot Master of Arts. signed

11 II ACKNOWLEDGEMENTS

The completion of this thesis is due in a large part to the aid and assistance which have been rendered to the writer by several individuals and organizations. Appreciation is especially extended to Dr. c. Lynn Hayward, the writer's Special Thesis Committee chairman, and to Dr. B. F. Harrison, committee member. Dr. Hayward has given freely of his time and knowledge in guiding the thesis work; Dr. Harrison has made many valuable suggestions and helped greatly in the identification of plants occurring in the study area. I wish also to thank Dr. Vasco M. Tanner, chairman of the Department of Zoology, and the other members of the department faculty for the advice and assistance which they have given to the writer for the past several years. I am also grateful to the Salt Lake City office of the United States Weather Bureau who kindly furnished the official weather records which were incorporated in the study, and to the Western Photography Laboratory of the Department of Agri- culture who made available the aerial photograph of the study area. Finally, I wish to thank my wife, who has been most patient in helping with the typing of the manuscript.

111 TABLEOF CONTENTS Page LIST OF TABLES • • • • • • • • • • • • • • • • • • • V LIST OF ILLUSTRATIONS. • • • • • • • • • • • • • • • vi INTRODUCTION• • • • • • • • • • • • • • • • • • • • 1 Previous Literature Area of Study

PROCEDUREAND METHODS• • • • • • • • • • • • • • • • 6 FACTORSOF THE PHYSICALENVIRONMENT. • • • • • • • • 11 Temperature Precipitation Wind Sunlight Over-all Seasonal Changes General Summary of Climatic Factors

VEGETATIONTYPES • • • • • • • • • • • • • • • • • • 20 Cattail-Bulrush Type Willow Type Wet Meadow Type Dry Meadow Type Deciduous Tree Type

COMPOSITIONOF THE AVIFAUNA• • • • • • • • • • • • • 27 Bird Species Present Census Results and Populations Distribution or Birds in Vegetation Types

DISCUSSIONOF INDIVI'DUALSPECIES. • • • • • • • • • • 46 SUMMARYAND CONCLUSIONS • • • • • • • • • • • • • • • ,9 LITERATURECITED ...... 63

iv LIST OF TABLES

Table Page I Comparative Weather Data; Long-time Averages Compared to Winter of 19,0-51 •••••••• 12 II Passerine Birds Observed at Utah Lake, Winter ot 1950-,1. • • • • •• • • • • • • • 28-29 III Census Results and Number per Hour f'or Most CommonBirds •••••••••••••••• 31

V LIST OF ILLUSTRATIONS Figure Page 1. Aerial Photograph of the Area or Study ••••• 4 Outline Map or the Study Area, Showing Census Route •••••••••••••••••• 8 3. Growth or Testes as Correlated with Increasing Periods of Daylight ••• • • • • • • 18 4. Plant Types Occurring in the Study Area •• • •• 21 ;. Total Number Recorded for CommonPasserine Birds •• • •••••••••••••••• • • • 33 6. Field Census No. 14. • • • • • • • • • • • • • • 35 7. Field Census No. 24 •• • • • • • • • • • • • • 36 a. Field Census No, 19 ••••••••••••••• 37 9. Field Census No. 48 ••• • • • • • • • • • • • • 38 10. Presence of Passer1ne Birds by Months in the Area or Study ••••••••••• • • • • 40 11. Graph Showing Relative Stability and Instability of Song Sparrow and Redwing ••••••••••• 42 12. Distribution of Passer1ne Birds 1n Vegetation Types •••••••••••••••• 44

13. Field Census No. 47 •• • • • • • • • • • • • • • 48 14. Field Census No. 6. • • • • • • • • • • • • • • 50 Plate I Photographs of Plant Types in the Study Area. • • • • • • • • • • • • , • • • , , 61 Plate II Photographs ot Plant Types in the Stttetf Area• • • • • • • • • • • • • • • • • • 62

vi INTRODUCTION

Ornithologists are generally prone to show great interest in that period of the life or the bird which embraces the breeding cycle. This interest is perhaps natural, since climatic and biologic conditions are nearly ideal for field work and observation during the spring season when most breeding activities take place. Of equal importance, however, and indeed exerting an even greater biological influence in many respects, is the period covered by the winter months. From an ecological point of view this is one of the most critical periods that the bird must undergo. As a result many birds which are summer residents in areas subject to harsh winters perform the routine and familiar migrations in order that the winter months may be spent under more favorable climatic conditions. There are many kinds of birds which, nevertheless, are known to remain in or near the same general region throughout the various seasons and aspects; these are classified as permanent residents. Such groups of birds are often Joined in the late autumn by birds of another category, the winter visitants, who may move in from areas of higher altitude or latitude. In this manner a wintering avian population is established which, in certain areas, may be of considerable size. Such a winter population must be equipped to meet a variety of situations, of both a physical and biological nature.

l 2 In the course of the present study the investigator has kept under surveillance the passerine birds which spend the winter months in a certain area adjacent to Utah Lake, near Provo, Utah. The approach to the problem has been largely of an ecological nature, with major stress placed upon such factors as relative numbers or bird species present, distribution or species according to vegetation types, response of birds to climatic changes, movements of birds in the area, and various other phases of their winter habits. The purpose of the thesis which follows is to analyze the data which relate to the above- named factors and draw whatever conclusions appear to be valid.

Previous Literature Little previous work has been done on the birds wintering in Utah Valley, although Hayward (1935) has contrasted the winter bird lite of Bear Lake (Idaho) and Utah Lake valleys, and further discusses (1948) the birds of the winter aspect in his study of the Wasatch chaparral. These two papers apparently constitute the only published work relating directly to the winter activity of passerine birds in this area. In addition there have been a few seasonal food studies made, particularly those or Liddle (1936) on the rood habits of the English sparrow in Utah Valley, and of Frost (1947) on the food habits of the birds of the Wasatch chaparral. It should be repeated that not a great deal of the above work is applicable to the present area or study. Meager as such local information may be, there has been no dearth of background literature relating to the ecological, 3 physiological, and distributional aspects or birds wintering in other parts of the country, or to winter bird life as a whole. Some of the conclusions drawn from studies which were made in other localities have been utilized in certain aspects of the present work. References will be made to this type of literature throughout the body of the text, wherever such information was drawn upon.

Area of Study The area chosen for the study was a relatively narrow segment of the Utah Lake shore lying four miles directly west of the city or Provo. The elevation at this location is 4,490 feet above sea level. Rather definite boundaries were set up to delimit the study area (Fig. l). The north boundary was marked by Provo River, while the southern limit was arbitrarily chosen as a point 1.7 miles south of the river. The open ex- panse of Utah Lake was utilized as the western boundary, while on the east the area was bordered by the Provo airport and cultivated fields. By way of over-all measurements the area was thus approximately 1.7 miles from north to south, and ranged in east- west width from a minimum of about 100 feet to a maximum of over 1,000 feet when the lake was at its lowest level in the autumn. This particul&r area was chosen for the study for two major reasons. First, it appeared to be an area which would lend itself well to a winter bird population study, since it was almost a separate entity, that is, a relatively undisturbed area surrounded for the most part by cultivated fields; and secondly, the area was readily accessible by automobile, even Fi~. 1.--Aerial photograph of the area of study. The dashed line indicates the boundaries of the study area proper. On the left is Utah Lake, and at the right is the Provo Municipal Airport. Scale: one inch equals 1,000 feet .. 4 5 during the heaviest snows of winter. Lying as it does in such close proximity to Utah Lake, the study area 1s subject to frequent inundations by the waters of the lake with subsequent emergences. In the past there have been great variations in the water level of the lake. For instance, during the prol~nged drought period which oceured in the fourth decade of the present century the water level or the lake was so low that it was possible to walk out on the mudflats for at least one-quarter of a mile before encountering water. For the past several years, however, the level of the lake has remained more or less constant, although exhibiting typical seasonal variations. When the present study was begun in the fall of the year, the actual shoreline was in some places more than 1,000 feet west of the eastern boundary of the area. On the arrival of the spring aspect, however, shallow water ap- proached to within fifty feet of the east limits in most parts of the area. Conditions are such that a rise in the surface level of the lake of only a few inches inundates relatively large adjoining areas or land. Such fluctuations of water level have a profound influence on the types of vegetation to be found in different parts of a lake shore community. This subject will be treated in more detail in the section on plant types, which follows below. PROCEDUREAND METHODS

In order to give a fairly complete picture of the winter bird populations of this area, includi~g the population transitions from autumn to winter and from winter back to the beginning of spring, the field work was carried on for a period of almost six months, from the end of October, 19,0 to the beginning or April, 1951~ During this period a total or about 150 hours were devoted to field work within the area proper. From November 14 to April 5 the investigator visited the area on sixty-six days out of a possible 143. The greater part of the study is embodied in two major aspects. These are (l) the bird species present in winter and their relative numbers, and (2) effects or climate and other physical factors upon the birds. At the outset of the study an analysis of the winter food habits was also attempted 1 but this project later had to be abandoned since time was not available for a minute and detailed analysis of the stomach contents. To determine the relative numbers of species in the winter population a special census method was evolved. Although precise quantitative counting methods are preferred in modern ornithology (Kendeigh, 1944), an exact count or all individuals in this area was not attempted. There were several reasons for this, among them the fact that the size of the area and its partial inundation would have made an exact enumeration of all

6 7 birds nearly impossible; also, there were present large flocks containing many hundreds of individuals of such species as the blackbird which could not have been counted with complete accu- racy. It was believed to be more advisable, therefore, to make a regular census tour or the area two or three times each week, counting and recording the number of passerine birds actually seen or heard within the area. Birds seen merely flying over the area have not been counted, unless they were subsequently seen to alight within the established limits. Using this method only a portion of the exact total population 1s accounted tor, but a good idea or the relative numbers of each species present is obtained. Essentially the same census route was taken each time (Fig. 2). Some modifi- cations of the route were necessitated from time to time owing to seasonal changes in the lake level. A group of standard symbols was used for the bird species, and as a bird was seen the appropriate symbol was marked on the census chart in the approximate position where the bird was observed. A separate chart was used for each census. Examples of daily censuses are included in the section on population results. The quantitative figure employed for comparisons between species has been designated as the number per hour; this is obtained for each species by dividing the number of birds of each species seen by the number of hours spent in the field. This census method was not put into actual practice until November 16. From that date to the following April 5, a total or ;o censuses was taken. The majority of the census 8

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/ ....-\ / \ / \ moat '------\«=~======UTAH I 'I PROVO I I CIT! I 'I AIRPORT I I LAD I I I symbol number I o Redwing- 'I \ + Song sparrow- I L:l. Crow- I I A Goldfinch- I ® Tree .sparrow- \ I Marsh wren- I I T llagpie- I ® Chickadee- \ I J) Pipit- I R Robin- I shore I • Siskin- I M Meadowlark- l \ \ J J'unco- \ \ V Vespe~ sparro,- \ \ ' I A Sage sparrow- \ I \ I Shr!ke- \ I W Gambel sparrow- \I '

Seale: l" - 1000'

Fig. 2.--0utline map of the study area, showing by means ot red broken line the census field trip route. Arrows indicate the directioh of travel. 9 , work was done during the morning hours, in order that the results obtained would be uniform in respect to time of day and light intensities. A few, (6), however, were taken during the afternoon hours. The census route covered a walking distance of about four miles, and a complete tour required from one and one-half to two and one-half hours, depending upon weather conditions. In addition to the quantitative census work, general observations on the activity of the various species were made whenever the opportunity presented itselr. These observations were included in the tield notes, along with the results of each census.

A series of specimens was usually collected by shotgun one day a week. Gonads were removed from several of the male specimens and measured with vernier calipers; this was done in order to study the correlation between the seasonal growth or the gonads and the increasing length of daylight during early spring. Information on weather and climate is of major importance in a study of this type. The weather station at the Provo municipal airport records, among other things, the following types of information daily: maximum temperature, minimum temperature, kind and amount of precipitation, amount or snow on ground, and wind velocity and direction. It was indeed fortunate that thes• data were readily available for use in this study, making it unnecessary for the investigator to take weather readings each day personally. The long-time weather 10 records for Provo on file at the United States Weather Bureau records office in Salt Lake City were also consulted. FACTORSOF THE PHYSICALENVIRONMENT

Those species of birds whose habits and physiological processes are not adapted to withstand low temperature and other unfavorable winter conditions respond by migrating into regions that are more suited to their survival. The individuals which remain to constitute the wintering population are able, under most conditions, to cope with the difficulties imposed by the winter climate. As Kendeigh (1934) has brought out, the fact that a few species do survive the whole year round in a region from which other species migrate indicates that there 1s a difference between species both in physiological adaptations and behavior responses. Since the physical factors of the environment which are involved in a study of this type are practically all of a climatic nature, the following topics merit consideration at this point1 temperature, precipitation, wind, sunlight, and aspection- a.l weather changes in general.

Temperature The information regarding mean temperature given in Table l indicates that the seasonal mean temperature for the six-months period of Oetober through March for 1950-51 was slightly warmer than for the fifty-nine year average. In fact, March was the only month which had a mean below the long-time average. This higher seasonal mean was correlated with below 11 TABLE1 COMPARATIVEWEATHER DATA; LONG-TIMEAVERAGES COMPAREDTO WINTEROF 1950-51

Mean Temperature I Total I Tott!,l Snowfall I No. or Rainy I , asuti:su: · Month ~n ··--- I

Oct. 50.1 56.4 1.43 0.60 I o., I .o I ; I 2

Nov. I 38.7 41.3 1.20 2.16 3.4 1.0 5 I 6 .... Dec~ I 29.l 3;.o 1.44 1.48 10.3 4.0 7 11 f\)

Jan. I 26.1 28.2 1.52 1.26 13.5 15'.3 8 12

Feb. I 32.0 I 35.3 I 1.54 I o.65 13.5 5.5 8 I 9

Mar. 40.5 37.4 1.55 0.81 8.4 1.0 8 5 Seasona .Mean or I 36.08 I 3s.9 I s.68 I 6.96 I 49.6 I 32.a I 41 I 45 13 average totals or precipitation, including snowfall. The mean temperature for a season has little significance as far as effects upon living organisms are concerned. Of greater importance are the periods of time at which temperatures remain at a critical level (Kendeigh, 1934). The information which 1s given here (Table 1) regarding means and totals, there• fore, 1s submitted primarily tor the purpose of showing that the winter during which the study was undertaken was fairly typical for this region. There was only one day during the entire 1950-51 season when a temperature below zero degrees Fahrenheit was recorded. This occurred on February 1, when the temperature dropped to six degrees below zero. The minimum temperatures as a whole for the season were thus not very severe, and apparently presented no great problem to the wintering bird species. Kendeigh, in his work on environment in the life ot birds (1934), states (p. 313), "Low temperature, in itself, is probably not often destructive to birds because of the remark- able regulatory mechanism they have for maintaining body temperatures." The combination of heavier feathers in winter, con- centrations of fat, and the ability of the endocrine system to increase the rate of metabolism and body heat production, serves to protect the bird against cold temperatures. Kendeigb's experiments tended to indicate that low temperature becomes critical only when food is unobtainable for any prolonged length of time. Since some food W-dS always available throughout the study area in the form of seeds on tall weeds and other vege- 14 tation, even during the deepest snows, it is believed that low temperature is not ordinarily critical for birds in this locale. Furthermore, periods of cold weather were always followed by days with more moderate temperatures, during which there was a noticeable upswing in avian activity. Some aspects of this will be discussed more fully in a later section of the paper.

Precipitation The comparative information regarding precipitation {Table 1) shows that the winter period under consideration had a lower than average amount of precipitation, with a consequent lower total snowfall. The number of rainy days for the season was about average. Although there was almost twice the average amount or precipitation in November, all other months were below normal in this regard. Each month was also deficient in snowfall with the exception of January, when almost one-half of the seasonal total fell. Precipitation in the form of rain did not appear to be of sufficient amount and duration to do any great harm to the wintering birds. With rainfall, dire consequences result only when the plumage becomes soaked, causing accelerated loss of body heat and, in some eases, death (Kendeigh 1934, p. 386).

A few of the field censuses were taken during periods of rain, at which times it was noticed that a fewer than average number of birds were actively moving about. No doubt the majority had sought some type of cover, since vegetative cover was available in all parts of the area. Snow is a factor of major importance it it falls in 1; great enough quantities to cover and hide available rood sup- plies. Deprived of food, the birds show less temperature re- sistance. There was no time during the winter, however, when snow lay on the level ground in depths of more than six inches. Many tall seed-bearing weeds were thus left exposed and furnished a ready source of food for most of the passerine birds. Some of the larger species, such as the crow, which often fed on the ground layer, apparently found a few inches of snow no great obstacle to their foraging habits. During actual snowfall bird activity was noted to be at a minimum, most individuals seeking cover as in the case of rain.

Wind During heavy winds birds are usually inactive and seek shelter. The action or a breeze is to carry the body heat of a bird away faster; to quote Kendeigh once more (1934, p. 388), "subjection to wind decreases the survival time or birds at medium or low air temperatures; this is due to the excessive cooling produced as well as the probable greater exertion of the birds during a wind." Due in part to the proximity of the study area to the open waters of Utah Lake, winds are not uncommon. Wind veloci- ties are taken four times a day at the Provo airport. Records there show that during the period of study winds of twenty-five miles per hour or more in velocity occurred on twenty-five days, with ten such days being in the month of March. The strongest wind recorded was on ~arch 9, with a velocity of forty-one miles per hour. 16 In the process or field work, opportunity was often had to notice the effects of wind upon avian activit7. On the morn- ingot December l, when the skies were overcast with low clouds, a strong aold wind wa.s blowing in from the west across the lake. Although the airport bad not recorded the wind velocity at this hour, it was judged to be blowing at a rate exceeding thirty miles per hour. Few 1r any birds were seen in flight, and a total of only thirty-one individuals were recorded on the census tor th.at day. While this represented the record low tor number or birds observed on a single census trip, it was nevertheless indicative or the ettects or strong wind on bird activity in the area.

Sunlight The occurrence or bright sunny days during the winter serves to markedly stimulate the activity of birds. Dw-ing periods of bright sunshine in mid-winter, birds were observed to intensify their food-getting activities, and some individuals would begin to sing. On February,, when the air temperature rose to forty-tour degrees Fahrenheit after the season's worst cold snap, the warmer weather was reflected in the activities or the birds. Song sparrows were heard singing quite often, the tone quality closely resembling that of the spring songs. Red• wings were perched singly throughout certain parts of the area in a semi-territorial pattern, also singing profusely. This was the earliest date or the year when activity of this nature was observed, and it seemed to be correlated directly with the sunshine and warmer temperature. 17 In order to determine the effect upon the reproductive organs of increasing lengths or daylight, with concomitant in- creases in temperature and light intensity, a collection of male specimens was made and the testes removed and measured. Having used the findings of Bissonnette and certain other workers as a guide, Kendeigh (1941) summarizes in part his experimental work on gonad development as follows:

Due to lengthening days in spring a stimulus is received by the birds to which the pituitary gland responds. This gland releases increasing amounts of hormones that are carried by the circulatory system to the gonads and induce increased cell division and growth so that these organs increase in size. The results of the observations are shown in Figure 3. The testes were removed from male song sparrows and redwings and measured at their greatest length. Since more than one male individual of each species was usually collected on the designated dates, the average length of the testes for each day was used on the graph. The results indicate a definite correlation between increasing amounts of daylight and growth of the gonads.

Over-all Seasonal Changes The first snow of the season fell on November 15, when one inch was deposited. The last snowfall came on March 17, and also amounted to one inch. During the winter, snow did not remain on the ground for periods longer than a week at a time. Owing to low air temperatures, and in part due to its shallowness, Utah Lake is frozen over for a considerable period or time each winter. This year the lake was completely frozen 13:00 ------6 mm.

145'

:30 ~/ 5 mm. _,,,,/ Mar. :15

12;00 ~---= 4 mm. :45 ------13 (X).... :30 // ~------~ 3 mm• ---- :1; // ----- ~---·,.,.,,.------11:00 2 mm.

:45 10:30 _.______13 ._ 1 mm.

Hours & Minutes Length ot of Daylight Testes Fig. ).--Growth or testes as correlated with increasing periods or daylight. Solid diagonal line indicates increasing day length (periods shown on graph are maximum possible hours or sunlight for the date indicated). Growth of redwing testes shown by upper broken line; of song sparrow by lower broken line. 19 across by January 15, and began breaking up by February 11, leaving a period of less than one month during which the lake waters were iced over. Long-time residents of the lake shore area considered this to be a shorter period than average. This may have been due to the slightly warmer seasonal mean temperature. By late March, general spring-like weather conditions prevailed, with the maximum temperature reaching into the fifties and sixties each day.

General Summary of Climatic Factors Winters in the vicinity of Utah Lake, though replete with\snow, fairly low temperatures, and other adverse conditions, are 1evertheless mild enough that several species of passerine bird~ can thrive there in some numbers during normal winter seas~ns. Amounts of snowfall have never been observed to be grea~ enough to cover all available types of rood sources, thus perm~tting wintering birds to feed regularly. At no time during the ~rogress of the study did the investigator find birds which I had

I I I I VEGETATIONTYPES

The study area may be divided into a number of more or less natural units based on the appearance or the characteristic types of vegetation. Cottam (1926) has made an extensive study or the flora of Utah Lake, and recognizes many plant formations and associations in the valley. Only a few of these occur in the immediate area of study, and have been somewhat generalized for this presentation. These vegetation types or plant communities often overlap, but might be listed separately as follows: cattail-bulrush (Typha-9cirPH§) type, willow {Sali~) type, wet meadow type, dry meadow type, and deciduous tree type. The general areas in which the various types occur have been plotted on the plant type map (Fig. 4).

) Cattail-Bulrush Type One of the most extensive plant types occurring along the lake is the emergent vegetation, composed of cattails (Typha latifolia and I• angust1fol1a), bulrushes (§girpus amer1canyJ and~. 01nm), tules (~cirPUi validu1), and reeds (Phragmites communi§). The cattails and bulrushes are the type of vegetation which is found growing farthest offshore. Both the willow and emergent vegetation types occupy areas which are subject to seasonal inundations of water from the lake (Plate II, Fig. 1). In the spring these areas are usually covered by a few inches to a foot or more of water. With the advent or summer the level of

20 21

,,,...... ,_ .,,., \ / \ / / \ ------

PROVO CITY UTAH AIRPORT

LAKE

Legegg Willows

Poplars r:m-•• Emergent Vegetation

Wet Meadow

Dry Meadow

Water

Scale: l" - 1000'

Fig . 4.--Plant types occurring in the study area (generalized). Compare with aerial photograph (Fig. L). 22 the lake begins to drop and the shoreline moves farther out, leaving_ the willow and bulrush communities on exposed ground or standing in very shallow water. This was the prevailing con- dition in October, when the study was commenced. As winter wore on, however, the level of the lake began to slowly rise and the shoreline marched almost imperceptibly eastward, until by April the areas of emergent vegetation were once more covered with shallow water. The cattail-bulrush stands are valuable as cover for certain bird species, for instance the marsh wren. The seeds of these plants are also utilized for food to some extent • •

Willow Type The shore or the lake is intermittently fringed with 'small stands of willows, mostly the sandbar willow, Sali1 e~igua. These plants are seldom found growing to a height of more than ten feet. They are of practically no value as a source of food during the winter, but are utilized extensively as perching and roosting areas. The larger peach lear willow (S§lil amygdaloid~s) occurs sparsely, and is also used mainly for congregating. Tamarisk (Tamarix galliq~) is often encountered growing with the willows, although it is a form which may be found in any of the lake shore communities.

Wet Meadow Type The wet meadow areas, not as extensive as the foregoing communities, usually occur next inshore to the emergent vegetation (Plate II, Fig. 1). The wet meadows derive their name 23 from the fact that they too are inundated during the periods of high water. The dominant and associated plants are mostly grasses and small herbaceous weeds, conspicuous among them being the following: saltgrass (Distichlis stricta), foxtail barley (HQrdegm Jubatum), rabbitfoot grass (f.olypogQD. monspel1ens1s), dock (Rumll maritim~§), samphire (§§licornia rubra), and seep- weed (§uaeda sp.). Around the fringes of the wet meadow there often occurs a belt of the relatively short marsh bulrush (§cii- ™ Ealudosu§), which apparently forms a zone of transition between the catta1l•bulrush and wet meadow communities. Apparently the greatest contribution of the wet meadows to the winter bird life is in the form of grass and weed seeds which may be used as food, although many of the seed-bearing stalks in this community are short enough to be covered by snow for some periods of time,

Dry Meadow Type Next inshore is the dry meadow community, which occupies ground just high enough to usually escape seasonal inundations. In the locale of study the dry meadow type is confined to a relatively narrow strip, as it is bounded rather abruptly on the east by cultivated fields in the greater part of the area, Two classifications of dry meadow can be recognized here, namely a grazed portion and an ungrazed part. The grazed area lies south of a wire fence which marks the northern boundary of the airport property (Plate I, Fig. 2). These two segments present a markedly different ap·pearance, and there is a corresponding difference in the amounts of birds habitually present in each. Con• 24 sistently higher numbers or birds are accounted for in the ungrazed section than in the grazed area. The dry meadow is characterized by a tall growth or several species of weedy plants, chief among them being the _rollowing: bassia Dassa sp. prickly lettuce Lf;tctug1 scar12:t1 giant ragweed Iva xanthifolia tumbling mustard ~ltiS§ilUJI blue verbena Verbena hastata indian paint brush Castilleja exilis aster Astet frondosu1 goosefoot C~enopodiy ba§tattµY) " Chenopodium !fil?!.91 dock Rumex crispus burdock Arctium minus milkweed Asclepiasspecio~ white top ~ardar!a draba sunflower Heliantby§ @nnuus sowthistle f?onehus !\1H?et black nightshade Solanum I1gr9:m cinquefoil .f.Q~entil i l!ll§.g_QD monolepis Monolfil2ll nuttall!an& bugleweed l',,YCOJU:!IlucidU§ catnip Iiepet~ ca tart a The bassia is the most conspicuous and important ot the tall weeds, and covers extensive plots of ground on the east side of the study area. In the heavily grazed portions, where even the tops of the bulrushes have been grazed off in some spots, there is a definite tendency for cockleburs (Xagth1wg pennsylvanicµw and A• echinat\Y,!1) to become dominant, almost to the exclusion of other plant forms (Plate II, Fig. 2). A great deal of overlapping is evident between the wet and dry meadows. Many of the weeds which have been listed as typical for the dry meadow also occur in scattered spots throughout the wet meadow. There is thus no sharp demarcation between the • two, but rather a gradual transition from one type to the other. The plants of the dry meadow community form one or the most important sources of food tor the wintering birds in this area. On numerous occasions large flocks of fringillids have been observed feeding on the seeds or many of the tall weeds mentioned above. The main value of such plant species lies in the fact that they are tall enough to escape being covered by snow, and hence are available to the birds at the most critical times during winter. Certain bird species, mainly the sparrows, depend on these tall weeds for protective cover and perching places. When a portion or dry meadow was destroyed by tire in the northern part of the,,,area on April 2, the numerous song sparrows which had previously habituated the vegetative cover there were forced to seek new sites tor food and protection.

Deciduous Tree Type Trees may occur as single individuals in any of the other communities, but certain well defined stands are round near the river mouth and in spots along the lake shore (Plate II, Fig. 2). Many of these groups began their growth in years past, when lake waters were much lower than at present, with the result that the trees have since been largely killed by the returning waters. Some of the trees were planted around the sites of former resorts, at periods of low lake level. Most or the trees found here are narrow-leaf cottonwoods (Populus J!!!- gustifoliw~ although a few Lombardy poplars (f.opulJU, qigt§. var. italic1) are also encountered. Trees are used extensively in the winter as roosts and 26 congregating places by flocking birds such as crows and redwings. COMPOSITIONOF THE AVIFAUNA

Bird Species Present A total of twenty-four different species of passerine birds, including five migrants, were recorded as occurring in the area during the period of study. These species are listed ·1 on Table II, along with the total number of times that each was recorded, and the residence status of each species (subspecific names follow Woodbury, ,!l !l, 1949). It will be noticed that ten or the species listed are winter visitants which have moved in from areas or higher altitude or more northern latitude; eight are permanent residents; tour are summer residents which were seen either late in the autumn or early in the spring; and two are migrants or local transients. Records in the Brigham Young University ornithol- ogical collections indicate that the horned lark is often found as a winter visitant at Utah Lake, but none of these birds were seen during the present study. During late spring and summer the avian population or this locality presents a different picture from that of winter. Typical or the passerine birds of this lake shore area in summer are the redwing, song sparrow, marsh wren, yellow-throat, savannah sparrow, and vesper sparrow. Yellow warblers, robins, and magpies nest in the nearby trees. Almost one-half of the characteristic summer perching birds of this locality, then,

27 TABLEII PASSERINEBIRDS OBSERVEDAT UTAHLAKE, WINTER1950-51

Number Residence Family and Species Recorded Status• Family Corvidae American Magpie (.f!.sa. pica bHd1oni1) 142 PR Western Crow (Corvus Qrach1rhYncho1 besper11) 523 WV Family Parida.e Pallid Black-capped Chickadee (f!ru1 1trJcapillus nevadensi§) 137 WV(PR) Family Troglodytidae Western Marsh Wren {Telma.todxt!.1 Rilgstris plesiuf 242 PR Family Turdidae Western Robin (I,yrdus aigratori~I propinguu1 57 PR Mountain Bluebird (~ialia rn.YS..21- gu) l WV Family Motacillidae Rocky Mountain Pipit fil21n· 2J:et~a al ticglg) 93 Family Laniidae Great Basin Shrike (~1ntu1 &udovi- g1any§ ney1degsi1) 5 PR Family Parulidae Rocky Mt. Yellow Warbler ( Dendroi:ga · petechia morcomi) 2 SR Rocky Mt. Audubon•s Warbler (~en- groica @Qdubon1memorabiliJ 3 M Family Icteridae Western Meadowlark (~turnella !lll- lec!!.) 29 PR Yellow-headed Blackbird

28 TABLEII••~inued

Number Residence Family and Species Recorded Status* Family Fr1ngill1dae Western Pine Siskin ( ?12inu.~ piny y1gran&?> 39 WV Pale Goldfinch (S12inus ~r1st1§ all· ~) 428 WV (PR) Nevada Savannah Sparrow (Passer- gul\1,1 sandJ1Ch!JlSil nev1gen1i1) l SR Western Vesper Sparrow (fgoec!]f...l ugineu1 confini1) 16 SR Northern Sage Sparrow (Amphispizg belli neyadensis) 6 WV Montana Junco (luncg oreganu1 montanus) and other juncos 21 WV Western Tree Sparrow (Spizella arborea 9cbracer) 352 WV Gambel's Sparrowzonotrichit teucopprx1 gambelii) 2 WV Montane Lincoln's Sparrow (l!.1.2 ~RiJI lincolnil alticqla) l .M Mountain Song Sparrow {Melospizg melodia montaga) 2807 PR

•PR~permanent resident; WV-winter visitant; SR-summer resident; M-m1grant; (PB)-possible permanent resident.

29 30 are migrants. When the wintering population of the study site is compared with those of nearby areas which differ in environment, some variations are noted. Within the environs of Provo and other adjacent settlements, the cedar and Bohemian waxwings, western robins, and Townsend solitaires are often seen as individuals or in large flocks. Among the characteristic wintering birds to be found in the chaparral ecotone or the nearby foothills are juncos of several species, pine s1sk1ns, robins, Wood- house and Stellar jays, chickadees, and spurred towhees (Hayward, 1935, 1948). While some of these species are round occasionally at the lake, they do not occur there in large flocks as they do in the chaparral. These differences in populations no doubt reflect a basic difference in the winter carrying capacity and utilization of the chaparral and lake shore areas. Since the oak brush area is much more extensive and more heavily vege- tated, it can no doubt support a much larger and more varied winter population or birds.

Census Results and Populations In the fifty censuses taken between November 16 and April 5, a total of 11,197 passerine birds were observed and recorded. The individual counts varied from a low of thirty- one birds on December l to a high of 943 on January 4. The census dates and number of perching birds recorded for each day are shown on Table III. Since ninety-one hours were spent actually in the field taking the censuses, the average number or birds seen per hour TABLEIII CENSUSRESULTS AND NUMBER PER HOURFOR MOSTCOMMON BIRDS

Date Totals A B C D E F G H I Nov. 16 38 17 5 5 l 10 17 112 8 80 ; 6 4 8 22 265 171 55' ; 3 7 2 24 104 53 31 1 1 ; 1 5 l 28 88 l ;6 17 8 29 148 20 94 11 9 12 Dec. 1 31 8 19 1 2 5 582 515 40 l 11 11 2 2 7 90 72 l 11 l 8 95 10 69 7 2 5 2 11 398 235 57 85 12 l 8 18 162 84 63 1 6 3 3 2 27 135 3 44 9 60 7 4 8 Jan. 4 943 860 19 13 48 8 206 75 55 24 40 i 4 10 143 12 32 10 38 42 2 1 6 12 118 8 71 3 2 18 6 10 15 162 80 42 3 21 7 1 8 17 265 42 ?2 57 55 14 3 2 2 19 105 13 41 2 4 23 l l 23 137 34 65 6 6 6 6 2 6 l 25 110 16 61 l? 4 6 6 27 40? 234 44 118 4 7 31 81 56 4 3 2 15 Feb. 3 125 5 42 57 12 3 2 4 5 139 34 86 3 4 3 2 6 1 238 139 73 6 7 7 4 2 9 266 167 80 7 4 3 2 3 12 211 126 55 7 3 4 3 4 14 335 262 51 17 1 l 2 16 144 57 77 4 6 19 314 212 63 9 8 5 l 5 11 21 134 90 29 10 3 l l 24 352 292 44 7 9 26 175 75 65 9 10 11 3 1 28 199 89 73 15 17 5 Mar. 5 414 334 27 12 9 4 -2 8 9 7 264 134 72 16 27 7 ; 3 9 148 52 70 3 10 3 l 4 12 235 106 51 15 21 3 6 30 14 225' 88 96 12 15 ; 8 17 162 89 49 2 , 10 2 2 19 179 107 51 14 3 l 21 309 184 86 7 8 9 i 4 2 23 250 134 13 ; 8 1 2 2 27 295 185 ~§ 21 9 3 7 3 29 278 192 59 3 6 4 2 30 268 203 44 6 2 Apr. 2 306 243 27 7 6 18 ,, iO? 21~ 41 16 1 8 q Totals: 11.l<.J? f,,?QCi' 2t107 'i21 428 v,2 ?42 t42 l~? g~ No. per Hour; 123 68.2 30.8 5.7 4.7 3.8 2.6 1.56 1. 50 1.0 Code: A-Redwing; B-Song Sparrow; C-Crow; D-Goldfinch; E-Tree Sparrow; F-Marsh Wren; G•Magpie; ff-Chickadee; I-Pipit. 32 was 123. This average number in itself is not of any great significance, however, as it is the daily variations in numbers of birds which are of importance. It may be concluded from the results of the censuses that nine passerine species are important from the standpoint of numbers in thfs locality during the winter. These nine also probably exert the greatest influence on the community. Each has a number per hour rating ot at least 1.0 (see Table III). The total number recorded for each of these species during the period of study is shown in graphic form on Fig.,. Great differences in the total numbers recorded for various days can often be at least partially explained by weather conditions, some aspects of which have been discussed previ~ ously. The low number of thirty-one birds on December 1 was recorded on a day when a strong, cold wind was blowing in across the area from the west. There had been rain during the previous twenty-tour hours, and the sky was completely covered with a dense low overcast. Even larger birds had difficulty maintaining their equilibrium in flight against the wind. It was obvious that most of the smaller birds had sought cover as protection against the elements. Four days later on the morning of December 5, however, when a total of 582 birds were counted, the sky was only slightly cloudy, there was no wind, and the temperature had reached a warmth of forty-four degrees by 10:00 A.M. A second factor influencing the total numbers for various days is the relative activity of large groups of birds 33

_li.2.,_of Birds ------6500 ~------1 6000

~----iN------t 2000 1---...i.1------11500 ~--M------, 1000

300

1--~+---==----il00 i--~...,_-84---+---I 50

A B C D E F H I Fig. 5.--Total number recorded for each of the nine most important passerine birds of the study. A- redwing, B- song sparrow, C- crow, D- goldfinch, E- tree sparrow, F- marsh wren, G- magpie, H- chickadee, I- pipit. 34 which are transitory in habit. The redwing blackbird, for instance, is a bird which 1s constantly seen in flocks flying back and forth over the area. When a sizeable group of these alights within the area, it may have considerable bearing on the totals for a particular field census. A glance at the plotting map for January 4, for example (Fig. 6), shows that ot the 943 birds recorded for that day, 860 were redwings, most or which were included in one large flock. By way of contrast, the census map for January 31 (Fig. 7) reveals that no redwings

\ at all were observed, and the total of eighty-one other species of passerines which were recorded compares closely with the eighty-three other such species for January 4. The crow is another species which, although perhaps "typical" of this area in winter, shows nevertheless a high irregularity in numbers from day to day. The goldfinch and the pipit are other examples of birds which show great irregularities due to !look movements. Long-range changes in the composition of the avian winter population amount to still another factor which has influenced the daily totals. By use or the term "long-range" is meant the week to week and month to month changes of species among the birds which spend part or all of the winter in the study area. For illustration, we may compare the census results for January 17 and March 30 (Figs. 8 and 9). The former date is typical of winter proper, while the latter 1s at the beginning of spring. The species of birds present indicate an intra- seasonal trend. Although such permanent residents as the redwing, song sparrow, and marsh wren are present in some numbers 35

/\ +- / \ ... ,,,,,,,,,,, \ ~ .,,,,,,...-moat '------

UTAH PROVO CIT! AIRPORT 4 / (J LAKE symbol number O Redwing- 860 + Song sparrow- 19 Crow- 13 A Goldfinc ·h- 48 ® Tree sparrow- Marsh wren- 3 T Magpie- ® Chickadee- )) Pipit- R Robin- shore • Siskin- M Meadowlark- J Junco- V Vespe~ sparro,- A Sage sparrow- Shrike- W Gambel sparrow-

Sca le: l " - 1000'

Fig . 6 . - -Field Census no. 14, for January 4, 1951. 36

/"\ // '\ / // moat \ '------

PROVO UT~ CITY. AIRPORT

LAKE symbol number O Redwing- + Song sparrow- 56 6 Crow- 4 A Goldfinch- ® Tree sparrow- 3 O blarsh wren- 2 T Y:agpie- 0 Chickadee- )) Pip1 t- 15 R Robin- • Siskin- shore M Meadowlark- ;r Junco- 1 + V Vesper sparro~- A Sage sparrow- Shrike- W Gambel sparrow-

Scale: 1" - 1000 1 • ~,s

Fi.g. 7.~-F1eld census no. 24, for January 31, 19,i. 37

9o•• •.. ••-. a •••• • "'•••a

,/\ / \ ,,,,,.,,,, \ /,,,.,, moat \....______

UTAH PROVO CITl AIRPORT

LAKE symbol n1m1ber O Redwing- 42 + Song sparrow- 72 6 Crow.- 57 A Goldfinch- 55 ® Tree sparrow- 14 Marsh wren- 3 T Magpie- 2 ® Chickadee- 2 )) Pipit- R Robin- • Siskin- 18 shore M Meadowlark- ;r Junco- V Vesper sparro•- A Sage sparrow- Shrike- W Gambel sparrow-

Scale: l" - 1000'

Fig. 8 .--Fi eld census no. 19, for January 17, 1951. 38

UTAH PROVO CIT! AIRPORT LAKE symbol number o Redwing- 203 + Song sparrow- 44 L!!. Crow- A Goldfinch- ® Tree sparrow- Marsh wren- 6 T Magpie- 2 0 Chickadee- J) Pipit- R Robin- 3 shore line +- • Siskin- M Meadowlark- l ;r Junco- V Vesper · sparrol'- 5 A Sage sparrow- 3 +- Shrike- W Gambel sparrow- l

Scale: l" - 1000'

Fig. 9.--Field census no. 48, for March 30, 1951. 39 for both days, there is a marked difference in the other species -which go to make up the totals. The crow, tree sparrow, goldfinch,and pine sisk1n are typically encountered here on days in the colder part of winter. On the other hand, the vesper sparrow, robin, sage sparrow, and meadowlark do not generally put in an appearance until later in the winter, after the snow is off the ground. This phenomenon of changing intra-seasonal distribution, then, has greatly influenced daily census totals. Fig. 10, showing presence of several species by months, may help to emphasize this point. Again, further reference will be made to this aspect of seasonal movements in the section per- taining to individual species. Another thing which must be kept in mind with this type of quantitative census is that the different species of birds have different degrees of conspicuousness; this too may influence the census results to quite an extent. The song sparrow 1s flushed with ease and usually at some distance, and upon being flushed tends to come up out of the tall weeds or other vegetation where it has been foraging and fly for a short distance, thus making it even more conspicuous. The marsh wren has a contrasting behavior. This bird does not ordinarily tend to flush at all; 1n fact upon the approach of the observer it usually attempts to drop farther down into the vegetative cover, thus making it almost impossible to visually mark the presence

of the bird. This visual disadvantage is often overcome by the noisy habits of the wren. Even after dropping out of sight, the presence of the bird is usually noted owing to the rustling 40

Npy,ember December January February March

Magpie

Crow

Chicka- dee Marsq W:rerC

Robin

Pipit

Meadow- lark

Redwing

Siskin

G.old- finch Vesper Sparrow~---~~-----11------1-----i-.:

Junco

Tree Sparrowi------11--~ Song Sparrow

Fig. 10.--Presence of the fourteen most common species of passerine birds by,months in the area of study. 41 of the dry bulrushes as the bird moves about in the clump. The marsh wren often utters its characteristic loud vocal call notes which immediately betrays its presence, although the individual may be far out of visual range. The magpie, crow, and meadowlark are other examples of birds whose vocal conspicuousness makes them more readily accounted for in a census than some of the species whose habits are more secretive. In addition, birds or large size are naturally more easily seen and recorded than those of small proportions. All or the foregoing information relating to factors which may influence daily census totals raises the question as to whether or not the number per hour rating is truly indicative ot the intluence which the various species- exert. When the available census data 1s analyzed with this 1n mind, there 1s an indication that the number per hour rating has definite some' al 1 has less significance for 1 species, though t meaning for others. To illustrate this point a comparison may be made be• tween the redwing and the song sparrow, From the standpoint or total numbers, these are the two most important species in• volved in the study; hence an inquiry as to their relative significance to the area may be or some value.

It will be noted on Table III _, that the redwing has a number per hour rating or 68.2, which is more than twice that of the song sparrow, the latter having 30.8. Further reference ) to Table III, however, shows a much greater constancy in the daily totals for the song sparrow than for the redwing. When a portion of this record is expressed graphically, as in Fig. 11, 42

of Birds ¼o2 0

260

240

220

200

180

160

140

120

100

80 I I " ' ...... ----- ' I 60 --- I " \.__ I " ' ' v / "'' -- 40

0 Jan. 23 25 27 31Feb. 3 5 7 9 12 14

Fig. 11.--Graph showing relative stability in numbers for the song sparrow and relative instability for the redwing; total numbers recorded for each species for a typical ten-day period of the census record. Solid line - redwing; broken line - song sparrow. 43 the difference is even more evident. Two or three hundred red• wings may be counted on one day, whereas not a single individual is recorded on the succeeding day. The redwing is a comparatively wide-ranging bird which is able to utilize distant cultivated fields and other outside areas for tood, but the song sparrow appears to remain in a fairly limited area day after day, especially in the tall weeds where an abundant food supply in the form of seeds is readily available. On the basis of these comparisons there 1s a definite indication that the number per hour rating of the song sparrow is a true index of the relative numbers of this species in the study area. The 68.2 rating for the redwing, however, is almost meaningless as an indicator of relative numbers, due to the very marked daily fluctuations in populations of this bird. The rating itself, however, may have other value in that it indicates a difference in habit between two bird species such as these. The individual discussion or species to be presented below will help to demonstrate that the local population of song sparrows depends more, and in some respects exerts more influence, on the study area than does the redwing.

Distribution of Birds in Vegetation Types There was evidence gained from field observation which indicates that the winter birds or this area may be assigned certain plant communities as locations upon which they are more or less dependent. Accordingly, Fig. 12 shows the important birds of the area distributed through the vario~s vegetation types as they have been noticed by the investigator. While no 44

TYPHA WT & DRY WLLOWS TEES SCIRPUS MEADOWS

Magpie

Crow

Chick adee Marsh Wren

Robin

Pipit

Meadow lark

Redwing

Siskin

Gold finch Vesper Sparrow ..------t------+-----_.::'!'/j

Junco

Tree Sparrow 1----� Song Sparrow ---"

Fig. 12.--Generalized distribution of passerine birds in vegetation types of the area of study. 45 one species can be said to remain in and be entirely dependent upon a single plant type, there are nevertheless certain passerines that spend the majority of their time in a particular plant locality. The marsh wren, for instance, 1s seldom if ever seen outside of the cattail-bulrush communities. The dependence or the meadowlark on the dry meadows and open fields 1s another obvious example which could be cited in this connection. Some items which are apparently the controlling factors in bird- plant type relationships are rood availability, cover and protection, and suitability of plants for roosting and congregating places. DISCUSSIONOF INDIVIDUALSPECIES

All of the passerine birds encountered in the area during the period of study have previously been listed {Table II). Only the most important species will be discussed at any length. The nine birds having a number-per-hour rating of more than l.O will be considered first. Each of these will be treated in respect to seasonal movements, daily activities, and any other information which might be of interest.

Utah Redwing (Age1aiu1 2hoeniseHJ u~anens~1) Perhaps no bird is more characteristic of the lake shore marsh areas than is the redwing. Much has heretofore been said in regard to the movements and other activities of this species, but there are several other things which are deserving of note. When the study was first commenced it was observed that the redwing was usually seen in huge flocks. On November 14, for instance, a group estimated to consist of at least 1,500 individuals flew over the area. During the colder part of winter these large flocks were of common occurrence, never staying in one place for any period of time and often greatly influencing daily census totals, as has been brought out in a previous section. When weather conditions began to moderate, however, certain changes in the group activity of the redwings were noted. Flocks were broken up into smaller units, and beginning with February 10, single males beian to spend at least the morning hours on

46 47 definite perches from which they would sing quite regularly, especially on sunny days. This type of semi-territorial be• havior increased from week to week, until at the beginning of April the activities of the males were typical of phases of the early breeding cycle. Few if any females were to be found in the mid-winter flocks, but in early March they began to make their appearances in large numbers. At the end of the period of study, when the males had begun to establish territories, the females were still in flocks with immature males; this gave a somewhat diffuse pattern to the census maps, as single individ- .. uals were spread over the area and medium sized flocks were also present. When Fig. 13 is compared with Fig. 6, the patterns of distribution are seen to differ greatly; the effects of winter flocking on the one hand and spring territorialtim on the other are readily seen in these two censuses, which are typical for their respective times or the year. In the usual winter pattern of daily activities, the redwings leave the roosting area at daybreak and fly out in flocks to begin the day's foraging. They range in groups throughout the extent of Utah Valley, and are even seen quite often in the midst of towns and settlements. Cultivated fields appear to be favorite spots for foraging, since redwings are often seen in such fields along with crows. After a day o! more or less constant wandering, the flocks return to the lake shore roosting sites soon after sundown. Willows or poplars are usually chosen as roosts, although bulrushes and other types or emergent vegetation are sometimes used for this. 48

UTAH PROVO CIT! • AIRPORT • 02.0 LAKE symbol number o Redwing- 192 + Song sparrow- 59 6 Crow.- 3 A Goldfinch- ® Tree sparrow- Marsh wren- 6 T Magpie- 4 ® Chickadee- 2 J) Pipit- R Robin- 4 • Siskin- shore line M Meadowlark- 1 J Junco- V Vesper sparro,- 7 A Sage sparrow- Shrike- W Gambel sparrow-

7i 9s Scale: 1" - 1000'

Fig. 13.--Field census no. 47, for March 29, 1951. Note distribution of single male redwings and flocks of females and immature males. 49 It should be repeated that the redwing, due to its transitory habit, is difficult to deal with in a quantitative manner; hence the number per hour rating is almost ineffective with this species.

Mountain Song Sparrow (Melo§.121za melodia m2n~an1} Previous discussion has brought out evidence that the song sparrew is the most stable passerine bird to be found in the study area during winter. It has certainly shown less fluctuation in numbers from day to day then any other species, (Table III). Although many individual song sparrows may be encountered within a limited area, they do not tend to form flocks which act as a unit. They are the most typical birds of the tall weeds in dry meadow situtat1ons. Figure 14 shows how song sparrows favor the weedy areas in the north portion of the study locality. The same type of pattern for these birds was obtained with almost every census, and was the rule rather than the exception. A superficial examination of the stomach contents of several song sparrows showed that the diet consisted almost entirely of seeds from the weeds of these dry meadow areas. Male song sparrows 1 were heard singing intermittantly in October and early November; after this they were relatively silent until the first week in February, when a sudden change in the weather brought warmer temperatures. From this time on the singing increased and quality improved so that by the first week in April it had reached typical spring-time efficiency. Apparently the song sparrows use the tall weeds as cover for the night, rather than roosting in groups in larger ,o

+3 133 ....-"\ / \ :-tz.i) / \ .,,,,, moat '------

UTAH PROVO CIT! AIRPORT LAXE symbol number o Redwing- 20 + Song sparrow- 94 Crow.- A Goldfinc ·h- 11 .. ® Tree sparrow- ••••• ,i :. Marsh wren- 9 ••: + T Magpie- ••... ® Chickadee- 12 . •••0. J> Pipit- 2~ R Robil'll- 1 shore • Siskin- M Meadowlark- ;r Junco- V Vesper sparro , - A Sage sparrow- Shrike- 1 W Gambel sparrow-

Scale: l" - 1000' 1--0 'lJ o-+-- Fig. 14.--Field census no. 6, for November 29, 195'0. The m~jority of the total number of song sparrows are con- centrated in the tall weeds along levee in north of area. 51 vegetation types. On one field trip which was taken through the area in the semi-darkness or late evening, numerous call notes of the song sparrow were heard issuing from the weedy patches, indicating that the birds had settled down there for the night.

Western Crow (CorVY£ brachxrhxnehQ! nesperis) The crow presents an interesting problem in regard to its winter habits and distribution. Although a common winter resident of the valleys or Utah, it is not known to breed in any great numbers in this region (Woodbury, i1 !!l, 1949 1 p. 23). November 4 was the first day of the season that crows were seen in the study area. They were present in at least moderate numbers for most of the winter, becoming scarce by the middle or April. Like the redwing, the crow is a bird which fluctuates greatly in its numbers from one day to the next in the study area. Its number per hour rating or,.?, therefore, is of no great significance. The crows did not utilize any of the trees in the study area for roosting at night, but in mid-winter they usually arrived at the lake shore by 8:00 A.M. and remained until about 4:30 P.M. They would congregate in the dead cottonwoods in large numbers, often setting up a loud vocal barrage. They did not usually forage for food in the area proper, but flew back and forth to nearby cultivated fields -where they obtained, among other things, corn and other grains. On February 3 a group of about twenty crows %'ere flushed up from the ground in section A; close observation showed. that they had been teed1ng on a HISTORIAN'S OFFICE ,2 pile of fish viscera, left there by commercial fishermen who had been fishing through the ice and had chosen this spot to clean their catch. This was an indication ot the omnivorous nature or these birds. On subsequent dates, crows were often seen feeding on dead carp which had washed ashore. Soon attar sundown the crows would desert the lake shore study area and head for the roost. A crow roosting site was discovered in a group of dead trees on the south edge of Provo bay, a distance or four miles southeast of the study area. This was apparently the roost which was used by the crows of the study area, since a group which was followed from the lake shore one evening in mid-March flew to this location.

Pale Goldfinch (Spinus tristis pallidu1) The goldfinches are permanent residents of the valley, but ordinarily do not breed in the lake shore marsh areas. No great significance should be attached to their number per hour rating of 4!7, as the day by day census results (Table III) show that they may occur in numbers on certain days and then be absent from the area for severalSllCceeding days. Goldfinches were first spotted in the area on November 4, when a few were seen with a group or about fifty pine siskins. They were cecorded quite consistently throughout the months of November, December, and January. Beginning with the end or Jan- uary, however, their occurrence was quite rare, although they again appeared for a few days during late February and early March. By the middle of March they had all but completely disappeared from the locality, and had no doubt moved into the 53 nesting areas. There appeared to be a definite correlation between sojourns of the goldfinch in the study area and periods or snowfall. On days which were fairly warm, with little or no snow on the ground, goldfinches were seldom encountered. Im• .r ·: mediately after a snowfall, however, they were often present in flocks of moderate size. It is known that these birds occur in large numbers during the winter in the nearby Wasatch chaparral (Hayward, 1948). It is my opinion that during periods or heavy snowfall in the chaparral, the goldfinches are forced either by lack of available food or by competition with other birds, to work down to the lake shore areas, where much seed food is available on the tall weeds. Perhaps the comparatively heavier snowfall in the foothills hides many of the seed plants which would otherwise be available there. The goldfinch is almost exclusively a seed-eater, and flocks have been observed many times feeding on tall composites and chenopods.

Western Tree Sparrow {§ptztll1 arbore§ 2£qr1cea) The tree sparrow is a typical winter visitant in central Utah, since it breeds at more northern latitudes and migtates to Utah in the fall. A few were seen in November and December, but they occurred in greatest numbers in the period from January to the end or March. They had all left the area by the first week in April. The tree sparrow is one of the most characteristic of the wintering birds, and its n~~ber per hour rating of 3.8 is a good index, although it is often seen in small flocks of ten to twenty individuals. It mixes freely with other smalll ,4 fringillids sueh as the song sparrow and junco. These birds utilize the dry meadow areas as a source or food, eating quantities or weed seeds. It appears that they are found in greater numbers near trees, however, and they always take to the trees tor cover when disturbed.

Western Marsh Wren (Telmatodytes palustris £lesiu1) Although some individuals in the breeding population of the marsh wren are known to migrate south for the winter (Bent, 1948), there are many which stay in the region as permanent residents. At the commencement of the study there were usually several recorded on each field trip, but during the coldest part of the winter, beginning in January, very tew and occasionally none were listed {Table III). During the period that the lake waters were frozen over it was a rare occurrence to see or hear a marsh wren. No doubt this small and fragile-appearing bird remains fairly inactive in the vegetative cover during the coldest weather. As the days began to lengthen and warm up in March, however, the noisy chattering typical of the species was heard once more. The tules, bulrushes, and other types of emergent vegetation are the typical domain of the marsh wren, and it is seldom if ever encountered outside of such situations. Stomach analyses made during the period of study showed that insects constituted the greater part of the food, even in mid-winter. The aspect of conspicuousness in respect to this bird was discussed in an earlier section of the paper. Although the wren is quite secretive in its habits, I believe that the number per hour rating of 2.6 is a fair index; if anything, it might be a little low.

American Magpie (Pica R.is!. hudsooi1) The number per hour rating or the magpie (1.56) is probably the most accurate of any bird in the area. Although the7 occurred in sparse numbers, they nevertheless showed a great deal of consistency in occurrence from day to day. Mag- pies were absent from the area during the censuses only nine times, but the greatest number seen on a single field trip was only nine. They are known to nest here in the summer, and remains of old nests can be seen in some of the poplar areas. The winter behavior of the magpie presented nothing especially unique. They did not remain in any definite type of location within the study area but ranged and foraged widely, as is the habit of the bird in the non-breeding season.

Pallid Black-capped Chickadee (Parui ~tricapillus nevagensis) Black-capped chickadees nest in the woodland and tall shrubs of the nearby mountains and along some or the valley streams. They usually spend the winter in the foothills and valleys. Along the lake shore they occur in small flocks such as those described by Odum (1942 1 p. 505), who says, Chickadee flocks are rather loose aggregations of individuals; occasionally the flock 1s fairly compact and moves with a fair degree of precision, but usually it is a straggling affair. In the study area they are most often found in groups of six to eight birds. The re~orded numbers for the species fell off in 56 March, when many ot them apparently began their altitudinal migration for the spring season. The chickadees were most otten encoru1tered 1n treea, w1llowa,and tulea near the water's edgeJ here they occupied themselves with a vigorous "searching" feeding routine. Examin- ations or stomach contents revealed that most of the tood con• s1sted of insects, both larvae and adults. Perhaps these were dug out ot small holes in tree trunks and branches, or from the stems ot tulea and bulrushes.

Rocky Mountain Pipit (AntbMI1ain211tS11,t!sol1) This is yet another species which exhibits an altitudinal migration 1n northern Utah Pipits nest in the high alpine meadows of the mountains in the summer, and move down into the lo••' lands to spend the winter months (Bent, 1950). Although it occurred in small tlocks within the area on several census days, the pipit is not a truly important member of the wintering population or the study locale. It depends mainly on nearby areas

or cultivation for tood 1 and apparently wanders down to the lake shore occasionally to forage tor weed seeds. Otten the land immediately adjacent to the lake receives less snow then the rest of the valley; this makes it possible ror such ground feed- ers as the pipit to more easily obtain tood.

The following species occurred 1n quantitative numbers ot less than 1.0 per hour, and were not considered to exert much influence in the area or study. the discussion ot each species will therefore be brier. Western Robin (Turdu1 "migratorigs proninguug) Although the robin is a common wintering bird in Utah Valley, often congregating in huge flocks in canyons and foothills (Hayward, 1948), it was not present in the study area between the months or November and March. In late February the first individuals for the spring season were observed. Through- out March they were regularly present in small numbers. These were no doubt some of the individuals which would constitute the breeding population.

Western Pine Siskin (Sp!nu~ p!nu1 vagrans) The seasonal appearance of the siskin was brief, since it occurred at the lake only during late December and January. It is a typical winter bird of the chaparral foothills, and when seen in the area was always in company with its near relative, the goldfinch. Its feeding and flocking habits are very similar to those of the goldfinch.

Western Meadowlark (§turnella neglec,a) The meadowlark is a permanent resident which winters in the fields and open country of the valley. None appeared in the study area until mid-February; from that time forward a few were seen or heard every day.

Juncos, mostly the Montana Junco (jy,nco oreganus montanu1) This species never occurred 1n large numbers, as it had been expected to do. Juncos are one of the commonest types of wintering birds found in the valley and adjoining foothills. Those that were noted during the census study appeared in the ~8 mid-winter months only. They were most often associated with flocks of other small fringillids. ~-·· Western Vesper Sparrow (Pooecetes gramineus confinis) This 1s a summer resident which made an early appearance in the study area, and so was included in the census results. 7 Vesper sparrows first arrived in early March and were noted in increasing numbers for the balance of the study period. They utilize mainly the dry meadow communities, and their habits are similar to those of other sparrows.

Northern Sage Sparrow (Amph!§Pi&! bell! n1vadegs11) A few or these appeared in March, and probably occur sparingly throughout the valley, They are of no importance as members of the lake shore wintering population.

Great Basin Shrike (Lanig~ lud9v!sianus n1v1dens11) A scant number of these were observed in November and December, but they disappeared from the study area after winter set in. They played no great part in the economy or the locality.

Certain species such as the mountain bluebird, Brewer blackbird, and Gambel sparrow were seen on one or two occasions. These birds are common in the valley proper during the winter, but they obviously favor cultivated situations or stream.side thickets rather than the wild areas along the lake margin. SUMMARYAND CONCLUSIONS

1.- During the period or October to April of the winter of 1950•51, a study was undertaken of a population of passerine birds wintering at Utah Lake. 2.- The area chosen for the study was a narrow segment or the Utah Lake shore lying mainly between the waters of the lake and the Provo municipal airport. 3 •• The oject of the study was to determine what species of passerine birds were present and in what relative numbers, how they responded to climatic conditions, what seasonal fluctu• ations were evident, and any other pertinent information regard• ing the avian winter life. 4.- Approximately 150 hours were devoted to the field work, which consisted largely or taking a census of all passerine birds in the area two or three times each week. 5.- The over-all weather data for the year compared closely with the long-time seasonal means and totals, and indicated that although such factors as precipitation, temperature, and wind may often be severe, they are not critical enough to prevent a fairly large population of passerine birds from spending the winter months here. 6.- Five fairly distinct plant communities can be recognized in the area, namely the emergent vegetation type, willow type, wet meadow type, dry meadow type, and deciduous tree type. There is evidence which indicates that certain 60 passerine bird species are especially dependent on a particular type or types of vegetation. The plant comuities produce ample amounts of food to meet the requirements of wintering passer ines. 7.- Twenty-four species of passer1ne birds were seen in the area during the period of study. or this nuber, nine spe� c1es play an important part in the natural economy of the area. Such species as the song sparrow, marsh wren, and magpie are relatively stable in their nubers and occurrence, and have nuber per hour ratings which are significant. Other birds, among them the redwing, crow, and goldfinch, occur here in great nubers but fluctuate widely in day by day totals. Their nuber per hour ratings are comparatively meaningless as an index to relative nubers, but are significant in that they indicate different modes of habit for these birds. 8.- The writer believes that the foregoing thesis is a contribution to our knowledge of the wintering habits of perching birds in lakeside areas or central Utah. The aspects or the study wich I consider to be of greatest value are the determination of species which are present during the winter and their relative nubers, their daily activities and sea sonal movements, and their reaction to changes in weather. PLATEI

Fig. 1.--View in extreme north of study area; in foreground, plants of wet and dry meadow communities; in background, dead and dying poplars of the deciduous tree type.

Fig. 2.--Fence marking north boundary of airport property. Note in the grazed area in foreground that plants are closely cropped. Contrast this with the tall growth of weeds in the ungrazed area of right background, Left background, area of emergent vegetation.

61 PLATE II

Fig. 1.--Plant types: in foreground, wet meadow; in near background, emergent vegetation composed of Typha ssp. and Scirpus ssp.; in far background, a group of sandbar willows, Salix exigua.

Fig. 2.--View in south end of study area showing in the foreground an overgrazed area of wet-dry meadow now dominated by cockleburs, Xanthium ssp., and in the back- groqnd an area of deciduous trees, including poplars and peach leaf willows.

62 LITERATURECITED

Bent, A. c. 1946. Life Histories or North American Jays, Crows, and Titmice. u. s. Natl. Mus. Bull. 191. 1948. Life Histories or North American Nuthatches, Wrens, Thrashers, and Their Allies. u. s. Natl. Mus• Bull. 19 7• . 195'0. Lite Histories ot North American Wagtails, Shrikes, Vireos, and Their Allies. u. s. Natl. Mus. Bull. 197. Cottam, Walter P. 1926. An Ecological Study of the Flora of Utah Lake, Utah. Univ. or Chicago, Ph.D. Dissertation. Frost, Herbert 1947. A Seasonal Study of the Food of Some Birds of the Wasatch Chaparral. Brigham Young University,-Ma.ster•s Thesis. Hayward, c. Lynn 1935. A Study of the Winter Bird Lite in Bear Lake and Utah Lake Valleys. Wilson Bull., 4?: 278-284. 1948. Biotic Communities of the Wasatch Chaparral, Utah. Ecol. Monogr., 18: 473-506. Kendeigh s. Charles {934. The Role of Environment in the Life of Birds. Ecol. Monogr., 4: 299-417. 1941. Length of Day and Energy Requirements for Gonad Development and Egg-laying in Birds. Ecology, 22:·237.248. 1944, Measure$ent of Bird Populations. Ecol. Monogr.• 14: 6?•106. Liddl~, J. Doyle- 1936. A Studyiof the Food Habits of the English Sparrow1in Central Utah. Brigham Young University, Master's Thesis. Odum, E. P. 1942. Annual ¢ycle of the Black-capped Chickadee-3, Auk, 59 ,499-531. Woodbury, A. M., Cottp, c., and Sugden, J. w. 1949. Annotat•d Check-list of the Birds of Utah. Bull. Univ. Utah, Biol. Series, 11: 1-40. 63 ECOLOGYOF PASSERINEBIRDS WINTERINGAT UTAHLAKE

Abstract of

A Thesis submitted to the Department of Zoology and Entomology or Brigham Young University

In partial fulfillment of the requirements for the degree ot Master of Arts

by Joseph R. Murphy

June 1951 During. the period of October to April of the winter of 1950-51, an ecological study was undertaken of a population or passerine birds wintering in a segment of the Utah Lake Shore. Available winter weather data indicated that although such factors as precipitation, temperature, and wind may often be severe, they are not critical enough to prevent a fairly large population of passerine birds from spending the winter months in the study locale. Five fairly distinct plant communities can be recognized in the area. There is evidence which indicates that certain passerine bird species are especially dependent on a particular type or types of vegetation. The plant communities produce ample amounts of food to meet the requirements of wintering birds. It was found that nine passerine species play an important part in the natural economy of this area in winter. Such species as the song sparrow and marsh wren are relatively stable in their numbers and occurrence, and have number per hour ratings which . are significant. Other birds, among them the redwing and crow occur here in great numbers but fluctuate widely in day by day totals. Their number per hour ratings are comparatively meaningless as an index to relative numbers, but are significant in that they indicate different modes of habit of these birds. The thesis 1s intended to be a contribution to our knowledge of the wintering habits of perching birds in lakeside areas or central Utah.