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NORTHWESTERN UNIVERSITY LIBRARY Manuscript Theses
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NORTHWESTERN UNIVERSITY LIBRARY Manuscript Theses
Unpublished theses submitted for the Master’s and Doctor’s degrees and deposited in the Northwesterh University Library are open for inspection, but are to be used only with due regard to the rights of the authors. Biblio graphical references may be noted, but passages may be copied only with the permission of the authors, and proper credit must be given in subsequent written or published work. Extensive copying or publication of the thesis in whole or in part requires also the consent of the Dean of the Graduate School of Northwestern University. Theses may be reproduced on microfilm for use in place of the manuscript itself pr yided the miles listed above are strictly adhered to and the rights of the author arv. in no way jeopardized. This thesis by . 7 ............. has been used by the following persons, whose signatures attest their accept ance of the above restrictions. A Library which borrows this thesis for use by its patrons is expected to secure the signature of each user.
NAME AND ADDRESS
EFFECTS OF DIFFERENT PHOTOPERIODS ON BODY WEIGHT, FAT DEPOSITION, MOLT, AND MALE GONADAL GROWTH IN THE SLATE-COLORED JUNCO.
A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS for the degree DOCTOR OF PHILOSOPHY
FIELD OF ZOOLOGY
By Hudson Sumner Winn
EVANSTON, ILLINOIS June, 1950
TABLE OF CONTENTS Acknowledgment INTRODUCTION Review of Literature
Development of Experimental Plan........
MATERIALS AND METHODS The Experimental Subject........................... 20 Trapping............................................22 Banding
Maintenance Prior to Start of Experiments..........24 Segregation at Start of Experiments.
Procedures: 1. 2* 3. 4. 5.
Maintenance ...... 30 Periodic Observations .......... ..30 Sampling........................... 31 Measurements of Testes......... 32 Histologic Technique .................32
RESULTS Body Weight and Fat Deposition..................... 34 Molt................................................ 37 Testis Development...........
DISCUSSION AND CONCLUSIONS Body Weight and Fat Deposition..................... 43 Molt
Testis Development................................. 52 SUMMARY......... LITERATURE CITED VITA
TABLE OF CONTENTS (Continued) LOCATIONS OF TABLES AND FIGURES IN TEST
Table 0, Photometer Readings in Foot-candles.........29 Table 1, Body Weights Prior to Experiments......... ..34 Figures 1-12, Body Mean Weights and Fat Classes......34 Table 1A, Chronology of Weight-Fat Response.......... 36 Figure 13, Times of Fat Deposition by Majorities of Responding Birds.................... ...36 Figure 14, Sequence of Fat Deposition, Fat Loss, and Molt .......................... 39 Tables 2-7, Testis Data,.........
Figures 15-20, Testis Weights and Stages of Develop-ment................................... 40 APPENDIX Tables 8-19, Body Weights and Fat Classes Table 20, Dates Equivalent to Days After Start of Experiment Plates 1-6, Experimental Rooms and Equipment
I wish to express my sincere appreciation to Dr. Albert Wolfson, who suggested this problem and under whose guidance the research was conducted.
His generous assist
ance and enthusiastic counsel during the course of the research and the preparation of the manuscript are grate fully acknowledged.
1 INTRODUCTION Review of the Literature Man has teen curious about migrations undertaken by many species of birds ever since he first noticed their seasonal appearances and disappearances.
activity was observationally associated with certain seasons of the year, man has attempted to correlate such activity with recognizable factors of the external environment.
observational data have led to conflicting conclusions. Though numerous clues have been revealed, making certain environmental factors suspect, the inherently limited poten tialities of observational data alone, have prevented an elucidation as to how those factors might operate. The use of an experimental approach to this problem was initiated by Rowan (in 1924 e_t sea.Y.
He demonstrated that
it was possible to cause precocious gametogenesis in juncos by subjecting them to photoperiods of gradually increasing durations at the time of year when the gonads have reached their annual minimum in size and activity.
the short, natural, fall and winter photoperiods with periods of artificial illumination.
Various modifications of this
technique have been employed by subsequent investigators to manipulate the gonadal cycles of a wide variety of birds and other vertebrates, providing indisputable evidence that light affects the gonads. Among the other factors of the external environment which have been considered is temperature.
The potentially impor
tant role that temperature might play as a causative influence
2 in seasonal reproduction among birds is considerably diminish ed by the fact that Rowan fs (1989) initial experiments were conducted during the Canadian winter at subzero temperatures* The lowest temperature he recorded was -52° F.
reported that reproduction in pigeons is depressed by cold, but Bissonnette and Csech (1937) hatched pheasant chicks on Christmas Day, following a period of light experimentation. Kendeigh (1941) reported no significant differences in re productive response between English sparrows kept at 36° F. and at 72° F.
Burger (1948) stated that the testes of star
lings maintained between 90°F. and 100° F. were much larger than the testes of starlings kept at lower, varying tempera tures, when both groups were exposed to photoperiods of long duration.
The higher temperatures, however, did not induce
continued spermatogenesis when the duration of the photo period was reduced.
Burger concluded that external tempera
tures approximating the body temperature of the Starling neither suppress spermatogenesis nor cause regression of the testis. These and similar additional records in the literature show that external temperature exerts no prohibitive effect on the gonadal development of most of the birds studied. Once the breeding condition is attained, however, temperature has been shown to be correlated, at least in some birds, with egg size and number (Kendeigh, 1941; Lee, Robinson, Yeates, and Scott, 1945).
There is no evidence, on the other hand,
to indicate that temperature is responsible for the initiation
5 or the maintenance of progressive gonadal development, such as that resulting from light experiments. As far as is known, food, adequate in content and amount, plays no important role in the sexual development of season ally reproducing birds.
Food that is deficient in known es
sentials might be expected to produce metabolic abnormali ties among birds, but in such instances, food is acting only as a limiting factor in the matter of gonadal development. Bissonnette (1932b) maintained starlings on a low protein diet and found no sexual response even though the birds were exposed to photoperiods of long duration.
compared testicular responses in English sparrows, some of which were permitted to feed only during restricted periods, and others during the whole light period.
The amount of food
consumed was the same in each instance, and there was no dif ference in testicular response.
No evidence exists in the
literature to confirm the possibility that a specific ingre dient of food might activate birds sexually. There can be no doubt that in the external environment many supposed and actual factors exist which have not been considered here.
Their characters and their degrees of pos
sible influence on gonadal rhythmicity in birds remain to be clarified by experimental work.
Yet it is clear that of the
known factors of the external environment, light alone has been found capable of effecting complete spermatogenesis in birds which reproduce seasonally. If light is so firmly implicated by experimental evidence,
4 the question seems to lie in the possible modes of action of light.
From endocrinologic studies, gonadal development is
generally believed to reflect hypophyseal activity.
tropins, synthesized and released by the anterior lobe of the hypophysis are thought to stimulate the gonads, resulting in the production of gonadal hormones and gametogenesis.
concept infers that the hypophysis must,therefore, be con sidered responsible for the state of the gonads on the one hand, and implicated, on the other, with a series of events associated with the mode of action of light.
But how light
acts, what the series of events is, whether a specialized photoreceptor is required, and how the hypophysis responds if it mediates between the light stimulus and the gonadal state, are not known. One might expect to find the solution in the array of literature resulting from investigations of avian seasonal reproduction, but the data are so diverse that no single concept can be perceived to underlie all the derived conclu sions.
Contributing to the difficulty of analyzing these
data on a common basis are the range of choice of subject birds and the wide variety of conditions under which experi mentation occurred. The birds which have been studied experimentally belong to many species.
Some are wild; some are domesticated.
the wild birds, some are migratory, others typically resi dent.
Even within a species, as Wolfson (1940 et seq.) and
Blanchard (1941) have shown, there may exist migratory and
5 resident populations whose behavior under identical experi mental conditions might be expected to differ.
of experimental conditions described in the literature has impelled Burger (1949;22Q) to say, concerning one aspect, ’’..•experimental work of a quantitative nature should be done under standard conditions. defined.
These conditions have not been
Each worker has made his own conditions.*.”
The literature does provide, however, a record of twentyfive years of investigations, scattered and fragmentary though they may be, which have contributed the factual bases for a slowly evolving and frequently adjusted continuity of thought bearing directly on the problem of how light affects season ally reproducing birds, and ultimately on the problem of migration. The first contribution which related light and the gonad al cycle was made by Rowan (1929).
He concluded that the
significantly operative constituent of light in his experi ments was the daily increments of light intrinsic in gradual ly lengthened photoperiods.
These increments he considered
equivalent to those encountered in nature in the spring, as he says (supra cit. ;S05), ’'Short increases, such as obtain in a state of nature, appear to constitute an essential prin ciple.” Again, years later, in the consideration of the wide range of environmental factors which might affect the molt and gonadal cycles of three species of birds found a few degrees south of the equator, Moreau, Wilk, and Rowan (1947)
6 concluded, ”In final analysis it seems to Rowan advisable not to rule out the effects of the increases in day-length at 5° S., small as they are,”
The increments range annually up
to sixteen seconds a day at that latitude.
envisage a daily increment of a few seconds as effective.” They closed with the suggestion that
ments involving extremely small increments of day-length might settle the question.” But Rowan (op_. cit.) had already come to the conclusion, based on his ’’Experiment 5” (winter 1927-1928), that light was not concerned beyond permitting the birds to exercise. In this experiment, he subjected Juncos to lengthening periods of mechanically induced wakefulness following exposure to the same photoperiod daily.
By this means, he attempted to sub
stitute ’’compulsory exercise” in very dim light for the daily increments of brighter light he had used previously.
concluded (op. cit.:202), ”It is therefore suggested that the light increases in reality afford the birds the opportunity of increasing exercise and that this is the crucial factor in inducing the development of the gonads.” Bissonnette (1931a, 1937), using (resident) starlings and Rowan’s technique of a mechanical activator, attempted unsuccessfully to confirm Rowan’s hypothesis.
later modified his original hypothesis to extend the limited sense of ’’exercise” to ’’general activity” or ’’wakefulness”, and reported superficial success in an experiment wherein English sparrows and Juncos were subjected to successively
7 lengthened periods of mechanically induced wakefulness in total darkness.
But the details of this experiment do not
appear to have been published. Riley (1940) and Kendeigh (1941) revolved English spar rows daily in drumlike cages in darkness for periods equiva lent to those of usually added illumination and secured no gonadal stimulation that could be ascribed to the enforced activity.
Thornton and Cummings (1945) also pursued this
line of investigation in the English sparrow.
mented short photoperiods with periods of darkness charac terized by noise designed to maintain a state of wakefulness, but no gonadal stimulation occurred.
Starlings were kept
awake by Burger, Bissonnette, and Doolittle (1942), who used flashing light.
They showed that stimulation or no stimu
lation could be evoked by varying the duration of the flashes and the intervals of darkness between flashes. Benoit (1935, 1937) and Benoit and Ott (1944) undertook a long series of experiments employing domesticated Rouen ducks.
They clearly showed that gonadal stimulation by the
use of light could not be obtained without the presence of the intact hypophysis, a fact which supports the conventional view of the endocrinologic interrelationship of the hypo physis and the gonads.
Further experiments demonstrated that
light induced spermatogenesis in these ducks after optic nerves had been sectioned, or when the orbits of enucleated eyes were illuminated, or when the hypophysis alone, or when portions of the hypothalamus and rhinencephalon were illumi-
8 nated directly with a restricted beam of light* A number of investigators have considered the possible receptors for light.
Ivanova (1935) hooded the heads of
English sparrows and found that spermatogenesis was not sup pressed by the treatment.
She considers the plucked skin a
possible receptor for light.
But her results are not in agree
ment with those of Ringoen and Kirsehbaum (1939) who found suppression in six and activation in three of their English sparrows.
Benoit (1937) illuminated the plucked backs of
ducks whose heads were hooded without securing a gonadal response.
From other hooding experiments, he concluded
first that light in the region of the eye induced gonadal development, and later, that eyes are not necessary for a gonadal response to artificial light.
To explain his results,
Benoit postulated the existence of two separate mechanisms which, upon illumination, stimulate the hypophysis*
were termed the oculo-hypophyseal system and the encephalohypophyseal system.
He considers them capable of simultan
eous operation in the intact bird.
Thus, light could stim
ulate the eye, and at the same time, penetrate the tissues of the head, effecting hypophyseal activity and thereby, gonadal development. Many of the foregoing conclusions based on experi mental evidence seem difficult, if not impossible, to re concile in a unified hypothesis concerning the mode of action of light.
The accumulated data have tended, thus far, to
support two divergent views.
Rowan»s hypothesis has received
9 no corroborative support from the work of other Investigators. Rather, the work of Benoit, Bissonnette, Riley, and others has led to the conclusion that light itself, and not acti vity, is the real factor. Wolfson (1941) attempted to elucidate the problem by a critical--examination and discussion of the evidence offered in support of each view, and presented a new. interpretation of what he considered the valid evidence.
He raised fully
justifiable objections to not only the experimental proce dures and conditions, but also the interpretations of the data of several of these authors.
Frequently, their results
could be interpreted in more than one way.
The common ground
Wolfsqn perceived is the possible role of the hypothalamus as a timing center for the sexual cycle.
He considers light
important in the regulation of the sexual cycle in so far as it provides the usual stimulus for a conditioned response, wakefulness.
Other stimuli, auditory, proprioceptive, and
tactile, if they are of sufficient magnitude,are believed capable of effecting a state of wakefulness as well.
position of the hypothalamus, controlling wakefulness, seems strengthened by the fact that the hypothalamus is the center for temperature regulation and plays a part in fat metabolism. But Wolfson*s hypothesis, though promising, because it embraces even the most divergent and heretofore irreconcilable features of the "activity” and the "light” hypotheses, can not be considered at present much more than a possibility.
the writer*s opinion,neither can the other two which have been
10 subjected to some valid testing and been found inadequate. Some experiments have been performed in the attempt to correlate gonadal growth with recognized characteristics of light.
Wave length, intensity, and duration effects have
been studied in a number of species of birds. No evidence has been offered to showr that ultraviolet light is stimulatory or required for gonadal activation. The near infrared, according to Burger (1943) and Benoit and Ott (1938, 1944), who used starlings and ducks respectively, is not stimulatory.
Of the wave lengths within the visible
spectrum, these authors agree that the most effective lie in the yellow-red range, and that the far red is not stimu latory.
Burger (supra cit.) and Benoit and Ott (supra cit.)
as well as Bissonnette (1943a), using starlings, and Scott and Payne (1937), using turkeys, have found that the blue of the spectrum evokes little or no gonadal growth.
writer is puzzled by the degree of significance Burger (1949) seems to attach to this fact, in the light of thefol lowing passages quoted from his review article.
considers "Activity and Wakefulness" (p. 216), he says, "Strangely enough, the demonstrated fact that, for some species, the blue end of the visible spectrum fails to acti vate males, has not been mentioned in various arguments." Under "Photoreception" (p. 818), he recounts BenoitTs exper iments, "Gonadal response was slight when blue light was used and the eye kept intact, but when the eye was removed
11 and the hypophysis was illuminated directly with blue light, marked gnnadal response occurred,«
He continues (p. 219),
"...Benoit found that light could penetrate to the pituitary. The penetration was best with red rays, the rays that in the normal duck are the best activators of spermatogenesis.
different effects on the intact bird of various wave lengths of light would be explained as due to a differential absorp tion by the tissues of the various wave lengths.”
for attributing responsibility for gonadal response to cer tain wave lengths does not as yet seem substantial. Effects of light intensity on starlings were studied by Bissonnette (1931b et seq.).
He demonstrated that testi
cular development was enhanced, under long photoperiods, by increases in wattage of Mazda lamps between 10 watts and 40 watts, but that 50 and 60 watt lamps were no more effective than the 40 watt lamp.
When Bissonnette and Wadlund (1933)
equated, for heat intensity, a 200 watt Mazda lamp with a 1000 watt lamp, and equated the former with a sunlamp for luminous intensity, they found that the 200 watt lamp was more effective than either of the others.
stimulatory intensity for the Starling has not been estab lished, but Bissonnette (1932a) reported that an unmeasured, dim light did not stimulate, and that 1.7 foot-candles of red light were enough to produce stimulation.
(1939b), also working with starlings, found that successive increases of intensity from Mazda lamps between 25 watts and 500 watts, with a 10^-hour daily artificial light period,
12 were not stimulatory.
In these experiments, the intensities
of illumination did not substitute successfully for suffi ciently long photoperiods. Brown and Rollo (1940) found that intensity was a fac tor in the determination of whether nuptial or non-breeding plumage regenerated in plucked areas of the male African weaver finch, Buplectes (equals Pvromelana) franciscana /fide H. Friedmann, 1937, Bull. U.S. Nat. Mus. 153:4S2_7. In these experiments, natural daylight of 11§ hours was sup plemented by Si hours of artificial light of controlled in tensities.
An intensity of 30 foot-candles during the sup
plementary period was followed by regeneration of non-breed ing plumage, whereas an intensity of 250 foot-candles was succeeded by regeneration of nuptial plumage.
intergrades were found after exposure to intervening inten sities.
Rollo and Domm (1943) extended this work and found
that an intensity of 126 foot-candles was optimum for the initiation of molt and subsequent replacement by nuptial plumage, with a 14-hour artificial day.
Higher and lower
intensities were observed to have a retarding effect on the expression of nuptial plumage.
Though no histological examin
ations of the testes were made in these birds, macroscopic observations correlated large size with the incidence of nuptial plumage, and small size with its absence. Bartholomew (1949) reported, midway between the initia tion and the conclusion of the present study, that in the English Sparrow, an intensity as low as 0.7 foot-candle
IS induced the formation of sperm after 46 days of daily, 16hour periods of artificial light.
An illumination intensity
of only 0.04 foot-candle was sufficient to initiate sperma togenesis, hut it was not complete when the experiment was concluded.
During the winter, 10 foot-candles were as effec
tive as either 52 or 244 foot-candles in bringing about tes ticular activation, but more effective than the lower inten sities mentioned previously.
It should be noticed that very
low intensities are not completely effective, that low and moderate intensities are sufficiently high to be effective and, within limits, increasingly so, and that higher inten sities are not increasingly effective. Before the subject of effects of day length or photo period is considered, the preceding treatment of the effects of wave length and intensity should have made apparent the fact that the three are closely related characteristics of all light, natural or artificial.
As all three are opera
tive when any light is existent, the possible effects of each on gonadal activation are not separable experimentally un less provisions for controlling the other two are made. Since spectral distribution varies between lamps and may vary between intensities, steps must be taken to equate not only these variations, but also durations of photoperiod before differences in experimental results can be ascribed to intensity differences.
Conversely, if wave length ef
fects are being tested, care should be exercised to assure uniformity of luminous flux and photoperiod.
14 effects of day length or photoperiod should theoretically be evident after wave length and intensity factors have been made constant. Burger (1939a, 1939b, and 1940) demonstrated that sperma togenesis did not occur in the Starling when photoperiodic durations were gradually increased from 6 to 9 hours, and that spermatogenetic activity did not proceed at a reduced rate when hours of illumination were reduced from 20|- to 16. He concluded that the minimum day length needed for rapid proliferation of sperm was slightly less than 12| hours. Days of 10|- hours were sufficient to initiate spermatogenesis, but it did not proceed far, in spite of the provided high illumination intensities.
Burger concluded that spermato
genesis in the Starling is not induced by an increase or a decrease in day length as such, but because an absolute photo period is reached which is of sufficient magnitude in dura tion to be stimulating.
Rollo and Domm (1943) found a photo-
period of 13 to 14 hours to be optimal for inducing nuptial plumage in, the male African weaver finch, guplectes franciscana.
A photoperiod of 9 hours induced non-breeding plumage
in spite of an illumination intensity of 350 foot-candles (cf. Burger, 1939b).
Furthermore, any intensity between 7-l
and 126 foot-candles was sufficient to bring birds into the nuptial plumage, as long as they were exposed to photoperiods at the optimal 13 to 14 hours’ duration.
found that the winter days of 12 and 14 hours were as effec tive as days of 16 and 24 hours in the rate of spermatogenesis
15 in the English Sparrow.
The full breeding condition was
attained by some of his sparrows after 46 days of 10-hour artificial light treatment daily, but it should be noted that these very birds had been on an 8-hour schedule for about seven weeks previously.
In another experiment, one of two
controls kept on an 8-hour day showed some spermatogenetic activity.
Development of Experimental Plan The literature just reviewed was at hand only through 1947 when the decision to undertake the present study was reached.
The literature revealed certain provocative features
which led to the formulation of an experimental plan. First, almost all of the contributions to the study of avian reproductive periodicity, involving an annual cycle, were based on experiments of notably short duration, extend ing usually from a few weeks to several months. Second, there existed a relatively high incidence of irreconcilable conclusions derived from these researches which often contained hints, inferred or obscure, that more extended investigation might alter the picture considerably. Hope of resolving some of these discrepancies, and perhaps contributing a few more, prompted the decision to make an extended effort covering at least a year, and preferably a longer period, in whatever aspect of the problem was chosen. Third, the suggestion of a possible importance of the effects of day length or photoperiod on birds seemed to exist
16 In the more recent literature.
This suggestion was particular
ly apparent in those researches involving investigation of the effects of the three characteristics of light, wave length, intensity, and duration.
Work concerned primarily
with the first two invariably hinted that some duration ef fect, irreplaceable experimentally by variations in wave length distributions or by shifts in intensity, was operative. Furthermore, references were beginning to be made to rather well-defined, optimal limits of day length. For rapid production of spermatozoa in starlings, Bur ger (1939a et sea.) set the minimum photoperiod at slightly less than 12\ hours.
For nuptial plumage response in African
weaver finch males, Rollo and Domm (1943) determined that 13 to 14 hours was optimal.
This is the same photoperiod used
in the poultry industry to secure optimal egg production. Bartholomew (1949) found that the best relative increase in testicular response in his English sparrows occurred be tween 12 and 14 hours.
Especially notable here is that a
good approximation exists for an optimum day length not only for gonadal effects, even between species, but also for plumage effects. This consideration, though Bartholomews (op., cit.) supporting evidence was not available at the start of the present-study, made plausible the possibility that effects other than gonadal or plumage might also be correlated with a duration effect of light.
Wolfson (1940 et seq.) found
that differences in the gonad, weight, and fat cycles
17 existed between resident and migratory races of the Oregon Junco, Junco oreganus.
Blanchard (1941) reported that these
and also differences in molt program and song patterns exist ed between resident and migratory races of the White-crowned Sparrow, 7,onotrichia leucophrys. Fourth, although several species of birds had been studied experimentally since Bowan (1929), the literature contained but a small segment concerned with the Junco.
addition to Rowan, contributions had come largely from Miller (1938) and Wolfson (1940 et seq.). The realization that the same bird Rowan used, Junco hyemalis. is a regular migrant in the vicinity of Evanston helped to determine the selection of an experimental bird. It appeared to be in numbers sufficiently large to provide an adequate source of laboratory subjects without depleting the local avifauna.
Rowan worked with the "Cassiar Junco’*,
Junco h. connectens. but **connec tens’* is no longer recognized in the check-list of the American Ornithologists* Union /fide I. N. Gabrielson and S. G. Jewett, 1940, Birds of Oregon, p. 567__J,and is the same race known now as Junco h. cismontanus Dwight /fide A. H. Miller, 1941, Univ. Calif. Publ. Zool., 44:329/, thought to have arisen originally from hybridiza tion of Junco oreganus and Junco hyemalis.
The choice of
Junco h. hyemalis (Linnaeus) for experimental study was made with the hope that some of the accumulating data on nonmigratory (i.e., resident) wild birds and domesticated species might be found to be substantiated in a typically migratory
18 species, and vice versa. From these considerations, therefore, the decision was reached to conduct an investigation into the possible effects of day length on the Slate-colored Junco, Junco h. hyemalis. It was proposed to place and maintain groups of birds under laboratory conditions of fixed photoperiods of different durations, with the hope that if the experimental birds were sufficiently numerous to demonstrate average population rather than individual trends, significant responses would be evi dent within a year.
To establish the existence of possible
responses, the birds were scheduled to be closely examined weekly for noticeable changes in their appearance and cer tain measurable physiological states. Because the literature indicated that related .juncos showed annual cyclical variations in body weight, it was decided to place major emphasis on this promising means of attacking the problem.
For the purpose of determining what
conditions of body weight obtain in Junco h. hyemalis. the desirability of maintaining as large a colony of birds for as long a period as possible was obvious.
Hence, the ex
pected gonadal response was decided to be ascertained only incidentally during the first year, as the present methods for determining the state of gonadal activity preclude the survival of the subject bird. The first year’s experiment was planned with the view that it would be essentially exploratory in character.
plan of the experiment during the second year depended to a
19 large extent on the results of the first year.
As it turned
out, differential responses to light were revealed during the first experiment, and since the gonadal response had been relegated of necessity to a place of secondary importance, the decision was reached to place more emphasis on the inves tigation of gonadal response during the second year.
this reason, birds were scheduled to be killed and autopsied at rather regular intervals to gain a better impression of the differences between the groups of birds as to their degrees of gonadal activation.
At the same time, the general
procedure of the first year was again to be followed, pro viding what was hoped to be confirmation of the regularity of the responses other than gonadal.
The experiments were
initiated both years on the same date to show comparable results.
20 MATERIALS AND METHODS The Experimental Subject The,Slate-colored Junco, Junco hyemalis hyemalis (Lin naeus) is a typically migratory fringillid which breeds, ac cording to Miller (1941), in the boreal forests of Canada from the Arctic coast of Alaska eastward to Labrador, New foundland, and Nova Scotia, southward to New England, New York, and most of the states which border on the Great Lakes. It winters between November and March in the United States principally south of the breeding range, east of the Rocky Mountains, and south to the Gulf of Mexico. Because of its geographical location, Evanston is ideal for obtaining a large number and a homogeneous flock of juncos.
As it lies in the region of overlap between the
breeding and wintering ranges of J. h. hyemalis. theoretical ly more individuals pass through Evanston during the migra tory period than locations much further north or south* Since in theory the earliest as well as the latest migrants move through Evanston, a more extended successful trapping period during migration is possible here than in places further north or south.
Evanston lies far enough east to
make unlikely the trapping of individuals (j. h. cismontanus) resulting from hybridization of J. hyemalis with j. oreganus. and far enough west almost to preclude the possibility of taking individuals of the racer J. h. carolinensis. Juncos make excellent laboratory subjects.
21 to conditions of confinement within a few days of capture, and though they never lose their wild character to the point of domestication, they are not difficult to handle.
seed-eaters, their dietary requirements are easily met. withstand wide ranges of temperature.
Their frequent bath
ing and preening keeps their plumage in good condition. Their small, size permits caging of several individuals togeth er, simplifying the problem of demands for space.
as is known, J. h. hyemalis does not breed in captivity. Parasitic infestation is not uncommon, but does not seem to affect noticeably the juncosT health, except in ex treme cases where parasitism undoubtedly contributes second arily to a decline in health of birds already weakened by primary injury or disease.
The principal cause of death
among juncos in captivity is skull damage and simultaneously incurred cerebral hemorrhages resulting from birds’ fly ing into the tops and sides of cages.
Sometimes, as will be
mentioned later, birds survive such injury, but more often they suffer a decline in health evident from a sudden or gradual loss in body weight, and death.
This cause of death
is particularly insidious because birds kept in captivity for even long periods succumb without warning. vigorous health one day are found dead the next. reveals the cause.
Birds in The autopsy
Much less frequently encountered as
causes of death are accidents which occur in handling the birds, and infections.
The latter category includes liver
and kidney involvements, infections resulting from limb
fractures and aggressive pecking by cagemates.
vulnerabilities, juncos are generally hardy, disease-resis tant, and capable of long confinement without ill effects. Trapping In the autumns of 1947 and 1948, two trapping sites were selected, one on the Northwestern University campus, the other in the Dwight A. Perkins Woods, two miles west of the campus.
For the use of the latter site, permission was
secured from the authorities of the Chicago Park District. The traps at the Perkins Woods site were set and baited with Argentine grass seed at twilignt in the evening, suf ficiently late to avoid undesired trapping and retention of birds overnight.
The traps were thus made available to the
birds from dawn until about two hours after sunrise each morning.
At that time, the seed bait was left exposed and
the traps were removed.
The procedure at the campus site
was similar except that trapping was carried on during the daylight hours. In the autumn of 1947, it was not known whether juncos could be trapped in sufficiently lafge numbers to permit significant laboratory study.
Therefore, trapping of the
White-throated. Sparrow, Zonotrichia albicollis (Gmelin), was undertaken to provide a reserve supply of experimental subjects.
Between September SO and October 15, 59 sparrows
were taken in the traps, weighed, examined for fat condition, measured for wing length, banded, and maintained in the
As juncos were captured, the sparrows were
released in groups.
Between October 11 and October 22, 79
juncos were caught.
Another was taken November 5, and the
la.st one was captured November 8, making a total of 81, of which 39 were males, 42 females. During the fall migration of 1948, only juncos were trapped.
Between October 4 and December 2, a total of 152
juncos were taken.
Of this number, 91 were males and 61
were females. It is worthy of mention that all but two of the juncos captured in 1947 were taken in Perkins Woods.
ing year, all but one junco were trapped on the campus.
explanation of such an irregular record probably lies in the fact that during the intervening summer, Perkins Woods was converted from a nearly virgin state to an attractive bird park.
To accomplish this task, many of the trees were removed
and much of the ground cover was destroyed*
Banding Within a short time of capture, the juncos were brought to the laboratory in holding cages (plates 4a, 6).
sit, from Perkins Woods, the holding cages were enclosed in cardboard cartons, ventilated, but darkened to calm the ex cited birds.
In the laboratory, the holding cages were placed
under opaque black cloth until the birds were banded. Each bird was anaesthetized with ether, weighed immediate ly to the nearest 0.1 gram, and fitted with a numbered
24 aluminum band, provided by the U.S. Fish and Wildlife Ser vice.
The bird was then examined for fat condition and the
state of the plumage in terms of missing or recently renewed remiges and rectrices-.
The chord of the wing was measured
with calipers to the nearest 0.1 millimeter. Reference to Ridgway (1901) and Miller (1941) had indi cated that the point of approximate demarcation for wing measure between the sexes of J. h. hyemalis was in the neigh borhood of 75 millimeters.
This measurement was used in
conjunctionwith body weight and sex of each individual.
plumage to estimate the
This method proved to be 94^ ac
curate, as the sex estimates of only 11 out of 184 birds autopsied during the two years were found to be in error. After each bird was examined, it was returned to the holding cage and a card was filled out to include the fol lowing data: Band number Species, estimated sex, and wing measure Date, time of day, and place of capture Date and time of weighing Body weight and fat class State of remiges and rectrices Any unusual condition noticed, as missing eye or heavy infestation by lice or mites Maintenance Prior to Start of Experiments As soon as possible after the birds had been banded, they were placed in cages in Rooms 315 and 316.
No more than
seven birds were placed in one cage.
to females was about the same in all cages.
25 top and upper half of the sides of each cage were covered with opaque black cloth to quiet the birds. The cage used in this study is known as the "Hendryx Flight Cage” (Plate 4c).
It measures 23f” x 14J ” x 18”, is
constructed of welded chrome wire, and has a removable tray bottom.
It is equipped with three perches, and has two plas
tic hooded feeders.
The addition of a large gravity feeder
was considered necessary in view of the number of birds in each cage.
The principal item of diet was Argentine grass
seed, which was kept always in excess supply.
This was sup
plemented every fourth or fifth day with freshly prepared mixtures of Gaines dog food and water.
A Stender dish con
tained white sand, and cuttlebone was placed within' reach of the perches.
Water for drinking and bathing was provided
daily. During the period preceding the experiments, the natural daylight was supplemented by artificial illumination because both rooms containing the birds were typically dim for much of each day.
The supplementary light, however, was never
permitted to extend beyond the limits of the natural photo period.
To gain an impression of the health of the birds
during their period of adjustment to confinement, they were weighed and closely observed. Within this period ih 1947, three birds were released, five succumbed to cerebral hemorrhages, and one was acciden tally over-anaesthetized, bringing the total number of birds available at the start of the experiment to 72 —
26 and 3? females. The following year, as the experimental emphasis was placed on the study of the male, many more females were trapped than could be accommodated at the end of the trap ping period.
Therefore, 29 females were released.
more, 13 birds died of cerebral injury, leaving 110 birds available at the start of the experiment —
82 males and 28
Segregation at Start of Experiments Numerous references in the literature indicated that several species of birds do not respond to light stimulation at all seasons.
Refractoriness to light stimulation appears
to be greatest in the fall of the year.
It became necessary,
therefore, to determine from the past record the optimum date to initiate the present experiments. Although Rowan (1929) obtained complete spermatogenesis in juncos in light experiments begun November 1, birds sub jected to lighting from October 2 showed only slight response. Riley (1936) demonstrated that immature English sparrows were capable of light stimulation as early as the end of September.
Riley (supra cit,) and Kendeigh (1941) have shown
that for the adults, the refractory period ends before the middle of November.
Wolfson (1945) obtained no response in
Oregon juncos subjected to lighting from October 18, but a few ;White-crowned sparrows showed a response.
27 illuminated golden-crowned sparrows from October 10 without response and determined the end of the refractory period for immature and adult birds in November. From this information, the decision was made to start the present experiments no earlier than December 1 to reduce to a theoretical minimum the number of refractory individuals taking part in the study.
Because the delivery of some equip
ment the first year was delayed, December 5 both years became the day that the birds were placed under experimental condi tions. For convenience, the experiment initiated in the autumn of 1947 will be referred to henceforth as "Experiment I", and that begun in the autumn of 1948 will be referred to as "Experiment II". To assure a reasonable degree of uniformity among the birds in both experiments, some changes had to be made in their distribution among the cages.
These changes were kept
to an absolute minimum to avoid the disturbance of the birds1 peck-orders and their individually established adjustments to confinement. At the start of Experiment I only, an additional change was made in the birdsf distribution.
The heaviest and fattest
birds were removed and placed in a separate cage.
it was not known at that time whether juncos could tolerate continuous lighting, the heaviest birds were selected for exposure to that theoretically most rigorous lighting schedule.
28 Late on December 5, the cages of Experiment I juncos were placed in six different rooms, each with its own light schedule.
Four of these rooms were employed again the
following year for the same light schedules, but other commit ments on space necessitated shifts of two groups of birds during Experiment I, Birds designated as the control group were placed in Room 317 under natural daylight conditions (Plate 1).
were removed to Room 105 on January 17, 1948 for the balance of the experiment.
The principal difference in the loca
tions was that the former had northern and western exposure, whereas the latter had an eastern exposure.
II, the control group was located in Room 317. Juncos of the 9-hour group were initially placed in windowless Room 4.
On March ‘3 , 1948, they were removed to
a large, ventilated storage closet, Room 305a (Plate 2). This location was also used for the 9-hour group of Experi ment II. During the course of both experiments, birds of the 12-, 15|-, and 20-hour groups occupied respectively Rooms 316 (Plate 3), 214 (Plate 4), and 112 (Plate 5).
Room 316 was
equipped with double fitted curtains and could be considered a darkroom.
Rooms 214 and 112 had westward-facing windows.
Room 305, with a northern exposure, was used for the 24-hour group of Experiment I.
During Experiment II, the corres
ponding group used Room 315, with a window facing westward (Plate 6).
29 Sangamo automatic light switches were installed in rooms containing the 9-, 12-, 15|— and 20-hour groups to control the periods of artificial illumination.
Because of the
short photoperiods concerned in the 9- and 12-hour groups, they were not exposed to natural daylight, except when doors to the rooms were opened. In the rooms containing the 9-, 12-, and 20-hour groups, a 7^ watt "twilight" lamp provided a dim glow for a half hour before and after the regular light period to ease the awaken ing of the birds in the morning and facilitate their roost ing at night (Plate 3b).
A similar lamp was rigged for the
lBf-hour group, but it was in operation in the evening only, and for fifteen minutes.
From illumination intensity measure
ments made of the twilight lamp in Plate 3b, with a Weston foot-candle meter (model 756), the possible effects of the lamp on the experimental birds were judged negligible. The types of illumination were not identical in all rooms.
Only incandescent lamps illuminated the 9-hour birds.
The 12-hour group was lighted by white fluorescent lamps only.
The 15^-hour birds were illuminated by a combination
of incandescent and white fluorescent lamps, supplemented with daylight.
Incandescent lamps and daylight illuminated
the 20-hour birds.
Birds of the 24-hour group were contin
uously illuminated by white fluorescent lamps, supplemented by daylight. On a dull day each year, the illumination intensities within the cages were measured (Table 0).
These figures can
TABLE 0 Photometer Readings in Foot-candles* Experiment I Group
Control 9-hour 12-hour
105 305A 316
Cage 1 1 1 2 3 1 2 3 1 2 3 1
Top of Cage 49 43 101 140 56 200 270 160 170 120 65 140
Floor of Cage 17 55 56 70 36 50 37 36 51 44 40 98
Experiment II Control
1 2 9-hour 1 305A 2 3 (Exp.I cont.) 4 12-hour 316 1 2 3 (Exp.I cont, ) 4 (Exp.I cont,0 5 15f-hour 214 1 2 3 20-hour 112 1 2 3 315 24-hour 1 2 3
130 52 69 117 30 17 98 35 50 32 95 200 265 160 200 92 63 50 53 55
190 34 41 40 17 15 47 21 21 19 46 84 92 52 40 27 47 30 33 30
* Measured with Weston Photronic Foot-candle Meter #6350 (Model 614).
30 be considered nearly minimum readings and attributable mainly to the artificial light sources, since the supplemen tary daylight in those rooms exposed to it affected the read ings only slightly.
All readings were obtained by tilting
the cell until it was at right angles to the nearest light source. All the experimental rooms were equipped with Taylor thermometers which recorded the maximum and minimum air temperatures.
Maintenance A daily circuit was made of all the cages.
minimum air temperatures of the preceding 24-hour period were recorded.
Occasionally, lettuce or apple slices sup
plemented the rations. 2.
Once a week each cage was cleaned.
Periodic Observations As often as possible each group of birds was closely
examined and the case histories of the birds were brought up to date.
Birds of one group were placed in holding cages
and processed within a few minutes of each other.
was anaesthetized by holding its head for ten seconds in an ether bottle.
Extreme caution had to be exercised as birds
are highly susceptible to anaesthesia, especially after they have been very active.
If breathing ceased, artificial
respiration was applied, usually with success, by gently
stretching and relaxing the wings at a rapid rate.
was weighed as in the banding procedure and its fat class was determined by blowing on and disarranging the feathers in certain regions to reveal the visible fat.
The fat classes
as defined by Wolfson (1945:109) are none, little, medium, and heavy.
Notes were then taken on the state of the plum
age, primarily the remiges and the rectrices.
studied for signs of the initiation or progress of molt. Notations were made of feather loss or renewal.
At the suc
ceeding observation, note of progress was made.
unusual, such as plucked regions, injury, or presence of ectoparasites, was recorded on the case history card.
Sampling Juncos scheduled for sampling were weighed and examined
for the record and then killed with ether.
The head was re
moved and the skull immediately examined to determine the extent of ossification.
Birds with incompletely ossified
skulls were recorded as immatures.
The skin and aluminum
band were next removed and the humeri and the tibio-tarsi were cut.
A thorough macroscopic examination of the liver,
intestine and intraperitoneal spaces was regularly made for parasites.
Cestodes were frequently found in the intestine,
nematodes in spaces.
The bird specimen was placed as soon
as possible in Bouin»s fixative, later replaced by 70$ al cohol.
Measurements of Testes Two kinds of measurements were made in this study.
Testes of sampled juncos were measured for dimensions and weighed.
In the first instance, dissected, preserved testes
were measured for greatest length and greatest width to the nearest 0.1 millimeter, using a calibrated ocular micrometer. Care was exercised to make readings only after each testis had been oriented with its long axis as nearly as possible horizontal. Preserved testes, were dissected free of closely applied epididymides and weighed on a Roller-Smith precision balance to the nearest 0.2 milligram.
Since each testis was preserved
in alcohol and could not be permitted to dry out, a method was developed to keep the variables inherent in such weigh ing fairly constant.
Each testis was removed from its vial,
touched for an instant to absorbent paper to drain excess alcohol, placed on an aluminum foil weighir^pan and weighed. If a reading was not obtained within ten seconds, the proce dure was repeated after immersing the testis in alcohol once more.
In this way, the weighing pan was kept slightly moist
from succeeding readings, and as the weighings were continued without interruption, their accuracy was judged to be fairly good.
Histologic Technique The left testis of each autopsied junco, fixed in
Bouin»s fluid, was dehydrated, cleared, and imbedded in paraf fin*
Sections were cut at 5 and 8 micra.
slides were stained with Mossman*s modification of Harrisf haemotoxylin, and were counterstained with aqueous eosin.
34 RESULTS Body Weight and Fat Deposition The results of weighing juncos at times of handing and later in the period preceding the experiments are tabu lated "(Table 1).
The numbers of birds involved are partial
ly cumulative, since birds trapped early were weighed several times.
Though sex differences in body weight are known, no
a t t e m p t
was made to treat them separately.
are presented to show the average population body weight variability during captivity prior to experimental treat ment. Body weight and fat class determinations of the bird groups of both experiments are graphed (Figures 1-12).
bases for these graphs are tabulated in the Appendix (Tables 8-19). In the tables, only the last two digits of the bird numbers.are given for Experiment I*The bands are from series beginning with 47-12800.
For Experiment II, the last
three digits of two series of bands, 49-1500 and 49-1600, are used to identify the birds.
In the columns of bird
numbers, separation of birds according to cages is indicated by dashes. It will be noticed that only fat classes medium and heavy, designated "MIf and ”H fT, appear in the tables. For Experiment I, the records of 69 birds — females —
35 males and 36
are presented (Tables 8, 10, 12, 14, 16, and 18).
The records of 2 males and 1 female were withdrawn because
TABLE 1 Body Weights Prior to Experiments
Experiment I. (1947) Date
Experiment II. (1948)
Mean Wt. in grams
No. of birds
Oct.14 Oct,15 Oct,16
17.6 18.7 17,0
7 2 5
Oct.19 Oct.20 Oct.21 Oct.22 Oct.24
17.9 17.6 16.8 17.4 15.6
4 18 9 10 1
Mean Wt. in grams
No. of birds
Oct.20 Oct.21 Oct,22
18.8 18.7 19.1
12 10 4
Oct.25 Oct.26 Oct.27 Oct.28 Oct.29 Oct.30 Nov. 2
18.5 18.5 18.5 17.6 17.9 17.3 20.4
13 14 14 1 2 1 2
Nov.26 Nov,29 Nov.30
18.6 18.1 18.2
11 19 15
18.5 t oo n- to irt
3HniVa3dW 31 NV3W
Continuation of Figure 3A.
Legend is the same as for Figure 1.
NOV. OCT. SEP. AUG. JUL. JUN. MAY APR. MAR. FEB. JAN. DEC. SWVU9
BaniVdBdW 31 NV3W
The relation between body mean weight and fat classes in the 9-hour group, Experiment II.
Legend is the same as for Figure 1.
i n CM
I 1- I
N (D IO ^ lO C M C M C M C M C M
(VI O CMCMCM
L N —
N V 3 W AQO0
The relation between body mean weight and fat classes in the 12-hour group, Experiment I,
Legend is the same as for Figure 1*
NV 3 W AQ08
A. 3amvy3dW3i NV3W
Continuation of Figure 5A*
Legend is the same as for Figure 1.
NOV. OCT. SEP. AUG. JUL JUN. MAY APR. MAR. FEB. JAN. DEC. SWVU9
AO 0 9
J « 3 y n iv « 3 d W 3 i
The relation between body mean weight and fat classes in the 12-hour group, Experiment II.
Legend is the same as for Figure 1.
NOV. OCT. SEP. AUG. JUL. JUN. MAY APR. MAR. FEB. JAN. DEC N OV .
The relation between body mean weight and fat classes in the 15§-hour group, Experiment I.
Legend is the same as for Figure 1.
15 25 5 15 25 5 15 25 5 15 25 5 15 25 5 15 25
C M C M C M C M C V I C M C M C J
S W V M Q NI 1H9I3M N V 3 W AQOS
O o o o o o O