observations on the renesting behavior

OF THE RING-NECKED PHEASANT

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

John Lyman Seubert, B. S., M. S.

The Ohio State University 1956

Approved by:

Adviser Department of Zoology and Entomology Acknowledgements

The author is deeply indebted to Dr. Eugene H. Dustman, Leader, the Ohio Cooperative Wildlife Research Unit, for his generous and able guidance and constant interest during this study. The interest and valuable counsel of Dr. Charles A. Dambach, Director of Natural

Resources Institute, The Ohio State University, has been greatly appreciated.

Special thanks are due to Mr. Walter Hoy, statistician, the

Statistics Laboratory, The Ohio State University, for the statistical analyses used in this manuscript.

I am indeed grateful to Mr. Henry Marquette, owner of the farm property upon which the research area was located, for his interest and cooperation.

To the many persons who offered their advice and assistance in the field, I extend my thanks, particularly to Dr. Ernest E. Good,

Eugene Knoder, James Hume, and Ralph Andrews.

I am grateful for the financial assistance in the form of a

Research Fellowship granted by the Ohio Cooperative Wildlife Research

Unit and for the undeiwriting of the costs of this study by this agency.

To my wife, Jean, my heartfelt thanks for her encouragement, patience, helpful suggestions, and for the typing and proofreading of this manuscript. Table of Contents

Section

Acknowledgements ...... H

X. Introduction ...... l

A. Perspective...... 1

5. Objectives ...... 5

II. Description of the Study Area and Methods

of Investigation ...... 7

A. Location of Study Area ...... 7

1. Physiographic and Geologic Setting ...... 7

2. Soils ...... 9

3. Climate ...... 9

B. Description of the Experimental Enclosure .... 9

1. Size and Fencing ...... o...... 9

2. Vegetation on the Study Area ...... 11

a. Type and Arrangement of Vegetation . . . 11

b. Control of Vegetative Growth ...... 11

3. Predator Control Measures ...... 13

C. Study Methods ...... 13

1. Brood Stock 13

2. Observations of Brood Stock ...... II4.

3. Location of Nests ...... 17

I4.. Aging of Clutches and the Assignment of

Nests to Categories of Incubation...... 17

5. Disruption of Hens ...... 20

iii iv

Section

III. Results ...... 23

A. Behavior of Brood Stock in Relation to the

Enclosure A r e a ...... 23

B. Breeding Behavior ...... 23

1. Territorialism ...... 2k

a. Territorial Conflict ...... 2$

b. Aggressiveness and Dominance...... 25

c. Territorial Establishment ...... 27

1. Time of Establishment...... 27

2. Number and Sizes of Territories • . 29

3. Fluctuations in the Sizes of

Territories...... 29

U. Territorial Requirements ...... 29

5. Cessation of Territorialism .... 32

2. Non-Territorial Cocks ...... 33

3. Harem Formation ...... 35

a. Number and Sizes of Harems ...... 35

b. Stability of Harem Composition ..... 36

c. Dominance Hierarchy of Hens ...... 36

I4. Territory and Harem Relationships...... 39

5. Inter-Specific Strife ...... J4O

0. Egg Laying, Nesting, and Incubation...... 1*0

1. Hens Available for Nesting ...... Itl

2. Nest Establishment and Incubation ...... U6

a. Number of Nests Per Hen U6 V

Section

b. Nest Types and Clutch Sizes ...... U8

3* Egg Production and Fertility ......

Time and Duration of the Nesting Period • • . 55

D. Behavior of Nesting Hens , ...... 57

1. Behavior of Incubating Hens ...... 57

2. Behavior of Disrupted Hens ...... 60

3* Clutch Usurpation and Adoption ...... 62

U* Nest Desertion and Abandonment ...... 62

5- Location of Nests in Territories and in

Cover Stripe ...... 6I4.

6 . Renesting ...... 67

a. Nest Re-Establishment in Relation to

Stage of Incubation ...... 67

b. Renesting Interval ...... 6?

c. Avian Ovulation ...... 75

d. Renesting in Relation to Time of Season. 82

e. Reproductive Success in Relation to

Renesting and Hatching Peaks ...... 90

f. Renesting Activity as Indicated by Nest

Establishment and Hatching Curves , . . 101

E. Behavior of Hens with Broods ...... 106

1. Number of Clutches H a t c h e d ...... 106

2. Behavior of Hens at Hatching ...... 106

3* Movements of Broods 107

1|. Brood Defense ...... 107 vi

Section

$. Adoption of Broods ...... 107

F. Bird L o s s e s ...... 107

IV. Summary and Conclusions ...... 112

V. Literature Cited ...... 119

Autobiography...... 127 List of Tables

Table

1. Dates of Estaolishment and. Sizes of Territories

and Dates of Establishment and Sizes of Harems,

1950-1951...... 28

2. Harem Composition and Degree, of Initial Nesting,

1950-1951 ...... 37

3- Nesting Data, 1950-1951 1+5'

U. Nest Establishment and Incubation, All Nests,

1950-1951 ...... 1+7 5. Mean Number of Eggs for Various Types of Nests,

1950-1951 ...... 51

6. Clutch Sizes of First Nests and Renests, 1950-1951 • • • 53

7« Egg Production, 1950-1951 ...... 55

8. Nest Establishment Data, All Nests, 1950-1951 58

9. Nest Desertion and Abandonment, 1950-1951 ...... 83

10. Nesting of Harem Hens in Relation to Territories,

1950-1951 ...... 65

11. Hens Renesting After Disruption From Initial and

Second Nests, 1950-1951 68

12. Hens Renesting After Disruption From Initial and

Second Nests, 1950-1951 Data Combined ...... 70

13* Hens Renesting After Disruption or Desertion, 1950 . . . 83

ll+» Hens Renesting After Disruption or Desertion, 1951 . . . 81+

vii viii

Table

15. Pheasant Productivity as Affected by Renesting,

Hatching Chronology, and Nest Disruption at Various

Times During the Nesting Season ...... 9U

16. Dates of Initial Nest Establishment, 1950-1951...... 95

17. Potential Hatching Distribution, 1950-1951 ...... 96

18. Adult Bird Losses, 1950-1951 ...... 108 List of Figures

Figure

1. Map of Ohio Showing General Location

of Research Ar e a ...... 8

2. The Research A r e a ...... 10

3* View of the Research Area Looking Northeast...... j.2

J+* Attaching Plastic Marker to Hen Before Release...... l£

5. Hen with Plastic Markers and Leg Bands ...... 16

6. Incubating Hen ...... 18

7. Aging E m b r y o s ...... 19

8 . Hen Disruption Procedure ...... 21

9. Site of Disrupted N e s t ...... 22

10. Cocks Fighting ...... 26

11. Cock Territories, 1 9 5 0 ...... 30

12. Cock Territories, 1 9 5 1 ...... 31

13. Territorial Cock and Part of H ar em...... 38

1U. Dropped Eggs ...... U2

15. Dump Nest in Clump of Red Clover...... I43

16. Incubated N e s t ...... UU

17. Compound Dump Nest , ...... ip?

18. Periods of Nest Establishment, 1950-1951 ...... 56

19* Display of Pugnacious H e n ...... 61

20. Regression of Length of Renesting Interval on Stage of

Incubation at Destruction of First Nest, 1950-1951 . . . lb

21. Renesting in Relation to Time of Season ...... 86

ix X

Figure

22. Nest Estaolishment Data, Buss (19U6)...... 102

23. Nest Establishment Data, Initial Nests, 19$0-19$! . . . 10U

2k* Nest Establishment Data, All Nests, 1950-19$1...... 105

25. Avian K i l l ...... Ill I. Introduction

A. Perspective

Renesting following unsuccessful nesting attempts has been accepted as a common occurrence in the nesting behavior of the ring­ necked pheasant (Phasianus colchicus torquatus) which typically raises one brood each year. Although there are many references in the liter­ ature about the occurrence or probable occurrence of renesting by pheasants as well as by other avian species, few are based upon direct observation. Most of the investigators have inferred renesting on the basis of indirect evidence, i.e., final reproductive success, clutch sizes, time of season, type of nest site, and the amount of down present in nests (duck nests).

Hamerstrom (1936) considered some of the pheasant nests found in small grain as probable renesting attempts because of the lateness of the season. Errington and Hamerstrom (1937) considered the theoretical aspects of renesting, and evaluated nesting losses of pheasants in relation to brood success. They suggested that by renestings, a great majority of hens succeed in bringing off noim- ally satisfactory broods in spite of heavy nesting losses. Randall

(I9I4O) apparently distinguished renests by smaller’ clutch size and

-1- time of season and wrote that by renesting efforts, between 52 and

55 percent of the hen pheasants on his study area raised broods, although only 25 percent of all nests were successful. Knott et al.

(19U3 ) reported that a study of pheasant brood records for the year

19U0 snowed that eight percent of the broods resulted from renesting attempts, these broods averaging 3*8 young each as compared to 8.2 young from first attempts. Baskett (191+7) compared nest establishment curves from three years of observations on pheasants in Iowa, and stated that vagaries in the descents of nest establishment curves may be traceable to renesting.

Kozlowa (1914-7) studied the breeding habits of the pheasant

(Phasianus colchicus branch!) in Tadjckistan, near Afghanistan, and reported that "only hens that have failed in their first nesting attempts, usually lay another clutch." Hiatt and Fisher (19U7) described the reproductive cycle of the pheasant in Montana and re­ ported that nesting after July 1 was probably renesting. Yeager et al. (1951) found that unusually heavy snows in May or early June in

Colorado may destroy many nests, forcing extensive renesting and late peak hatches.

On the basis of his investigations in Michigan for the years 19 UO,

19i4l, and 19U2, Shick (195>2) was of the opinion that most clutches started after June 1 probably were renestings, since the height of the nesting season occurred during May of each year. According to Stokes

(195l4)j over-all nesting success on Pelee Island during 19U9 and 1950 was the result of excellent initial hatching success with little re­ nesting occurring. Bishop (I9 I4I4) observed the nesting behavior of -3-

25 individually marked pheasants in a Connecticut study and reported that one of the hens renested.

Errington (19U2) considered theoretical aspects of productivity in populations of higher vertebrates and formulated a method for analyz­ ing the productivity of a hypothetical species (similar in behavior to the ring-necked pheasant) based upon percent nest success, renesting, and the number of hens ending the season with broods. He concluded that losses of eggs or of young can be expected to cause increased breeding by a considerable variety of higher vertebrates. Cartwright

(I9J-U4) discussed the theoretical aspects of predation as a survival factor among renesting species, including pheasants.

Renesting has been observed in enclosure studies of pheasants conducted subsequent to the writer's study. In these studies, individu­ ally marked pheasants were confined to enclosures and their nesting behavior was observed. Smith (1953) reported that two hens appeared to have renested after having hatched broods from initial nests.

Muhlbach (195U) reported that renesting occurred in about one-fourth of all cases after nest predation, nest destruction due to farming, or nest desertion. He observed two hens renesting twice. In a study made by Semones in 195U, 25 of h9 hens that deserted initial clutches renested (Semones, 1956).

Renesting by pheasants also has been touched on by many other authors including leatter (19U6), Wight (1930), Wight, Jr. (1950),

Eklund (19i|2), Schroeder and Erickson (19iUi), Dustman (19U9), Erickson at al. (1951), Lyon (1952), MacMullan (1952), Salinger (1952), Carlson

(19U6), and Nelson (195U). It has long been known that many passerine species renest

(Errington, 191+2), and according to Lack (l9l+7a), single-brooded

species such as many Anatidae, Gallifonnes, and Ralliformes will lay

again if their first clutch is disrupted. Investigators also have

reported renesting activity for many other game species including: bobwhite quail (Colinus virginianus Subsp.), Stoddard (1931), Lehman

(1953)i Gambel quail (Lophortyz gambelii), Gorsuch (193U)j Hungarian partridges (Perdix p. perdix), Knott et al. (191+3), leatter (1931+),

Yocom (191+3), Lack (I9i+7b), McGabe and Hawkins (19l+6)j ruffed grouse

(Bonasa umbellus), Clark (1936), Edminster (191+7), Bump et al. (191+7), prairie chicken (Tympanuchus cupido americanus) and sharp-tailed grous

(Pedioecetes phasianellus campestris), Hamerstrom (1939), sooty grouse

(Dendrogapus obscurus fuliginosus Ridgway), Bendell (1955); eastern wild turkey (Meleagris gallopavo silvestris), Mosby and Handley- (191+3) ducks, Bennett (1938), Low (1 91+5), Kalmbach (1938^ Barnes (191+8),

Engeling (191+9), Glover (1956), Sowls (19l+9)(l955)*

Although renesting has been reported for the pheasant and for many other game birds, all but a few authors have apparently based their reports of this activity upon indirect evidence. The study of the renesting of ducks by Sowls (19i+9)(1955) appears to be the first intensive investigation of the renesting behavior of ducks or of any game birds. Sowls located 220 hens on nests, trapped, marked, and released them, and took the eggs from the nests. Forty-two of the

220 hens were later found renesting, and three hens had three nests during one season. -5-

A search of the literature has revealed few valid data concerning the renesting behavior of the ring-necked pheasant. Many investigators of the pheasant and of other species have reported low seasonal nesting success as Kalrnbach (1939) and Buss et al. (1951) have summarized, but when over-all productivity is found to be high, the successful hatch is attributed to renesting. This assumption appears reasonable

(Errington, 19h2). However, there is always doubt as to how much re­ nesting actually occurs because accurate figures usually cannot be ob­ tained for wild populations and large errors can be made by relying on estimates. The number of hens in a population cannot be accurately determined; all nests are usually not found; the loss of hens during the breeding season can only be estimated; there may be a differential egress and ingress of breeders with or without broods; and accurate nest desertion rates are not obtained.

B . Objectives

In recognition of the lack of accurate information about renesting by the ring-necked pheasant, an intensive study of renesting of a con­ fined population was conducted. The study was undertaken to attain the following objectives:

A. To determine the extent of renesting.

B. To determine the number of times hens will renest.

C. To determine if the stage of incubation at the time of nest

disruption has any effect on the likelihood of nest re­

establishment. -6-

D. To determine renesting intervals and if the length of the

intervals is affected by the stage of incubation at the

time of nest destruction.

E. To determine if clutch size and egg fertility are affected

by renesting. II. Description of the Study Area and

Methods of Investigation

A. Location of Study Area

This study was conducted in central Ohio on a 9-acre tract of leased farmland. The area was located in Delaware County, Section li,

Liberty Township, 1-l/U miles north of the town of Powell, which is

15 miles north of Columbus, Ohio. Geographically, it was located about

3/It of a mile north of the intersection of the lines of North Latitude

L0° 10*, and West Longitude 83° 03' (Fig. 1).

1. Physiographic and Geologic Setting

Delaware County is located in that portion of the state known as the Till Plain Section of the Glaciated Central Lowlands. The topogra­ phy of the county varies from flat to rolling. Drainage is poor in the flat areas and subsurface tiling has been done in the areas farmed.

(Westgate, 1926). The topography of the research area varied from flat to gently undulating. The area had been tiled, surface drainage was good, and no flooding occurred.

Both the Illinoian and Wisconsin ice sheets passed over the area, but regionally the drift is thin, averaging less than 25 feet. The general area is underlain by Ohio shale and Delaware and Columbus limestone, all of Devonian Age. Powell, at about 920 feet elevation, lies close to the base of the Ohio shale. Here, the top of the

Delaware limestone appears at approximately 860 feet, and the Columbus limestone occurs at 760 feet or lower (Stout et al., 19U3).

-7- -8-

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U C K M

Figure 1.

Map of Ohio Showing General Location of Research Area -9- 2. Soils

The soil types found on the study area are of the Miami Catena.

They include Crosby silt loam and Brookston silty clay loam, both

poorly drained soils found on the level areas, and Celina silt loam,

a well-drained soil, found on the gently sloping land (Solt, 1956).

3 . Climate

The climate of Delaware County is characterized by a moderate

continental type of climate. Mean temperatures range from 28.5°F*

in Januaiy, to 7U°F* in July* The average dates for the last and

first killing frosts are May lj., and October 8 . The average length

of the growing season is 157 days. The lowest mean monthly precipita­

tion occurs in February (2.18 inches) and the highest in July (U*06

inches), the average annual precipitation being 37*06 inches.

(U.S.D.A. Yearbook, 19ll)*

B. Description of the Experimental Enclosure

1. Size and Fencing

The study enclosure was rectangular in shape, 528 feet wide by

6148 feet long, and consisted of 7*85 fenced acres (Fig. 2). The fence,

of poultry netting, was about 7 feet high. The upper 5 feet was of 2- inch mesh and the lower 3 feet, 12 inches of which was buried, was of

1-inch mesh. The netting was suspended by hog rings from a wire

supported by wooden fence posts. The lower 12 inches of the netting was anchored in the ground by setting it in a plowed furrow which was then filled in. Entrance to the enclosure was provided by two gates, one at the east and the other at the west end of the area. Figure 2. The Research Area

j-J-— - Gate Acres Fenced - 7*35 Acres in Cover - 3*52 W ^ Tower Acres Without Cover - l+»33 Length of Area - 61*8' Width of Area - 528' Scale* 1"=96' -11-

^ * Vegetation on the Study Area

a. Type and Arrangement of Vegetation

The study enclosure was located in a field of first-year mixed hay. When the study was initiated, the principal plant species present were red clover and alfalfa, with some timothy, alsike clover, and white clover. The vegetation the second year of the study consisted mainly of timothy, with some red clover and alfalfa.

Before the experimental population of pheasants was introduced, the enclosure area was marked off into 33 strips, each 16 feet wide, running east and west. To facilitate the locating of nests and the observation of birds, the vegetation on alternate strips and at the east and west ends of the field was killed by cultivation (Fig. 3).

These bare areas were maintained throughout both seasons.

Shortly after the release of the birds in 195>1, brush was placed around the entire inside fence line of the enclosure and in piles about 8 yards from the fence to afford escape cover fox- the birds.

The brush was removed on May 30.

b. Control of Vegetative Growth

Once hens had begun to nest, the control of vegetative growth was attempted by the use of chemicals, since it was feared that disking operations might disrupt nesting hens. However, the use of herbicides proved unsatisfactory, and furthermore, it was found that disking apparently did not disturb hens nesting in the cover strips. Once this was known, disking was relied on entirely and was done as often as necessary to maintain the alternate strips relatively free of vegetative growth. -12-

Figure 3»

View of the Research Area Looking Northeast

Alternate bare areas and the cover strips in the foreground and observation tower in the background. -13- 3. Predator Control Measures

Predation by both mammalian and avian species is occasionally a

serious problem when prey species are concentrated. As described previously, the lower portion of the fence was buried in the ground.

This was done to prevent the entrance of mammalian predators and to preclude the escape of pheasant chicks. As other preventative measures,

an electrically charged wire was strung at the top of the fence around the entire enclosure, and jump traps also were set around the outside

of the enclosure fence.

No control measures were taken against avian predators in 1950, but in an attempt to reduce losses of brood stock, pole traps were

erected in 1951* both in and outside the enclosure. Most of the losses to avian predators occurred at night and were attributed to the great hom ed owl (Bubo v. virginianus). The almost daily presence of the investigator in the studyarea was believed to be a deterrent to diurnal avian predators.

C . Study Methods

1. Brood Stock

The brood stock, Phasianus colchicus torquatus, used during both years of this study was yearling birds obtained from the Urbana State

Game Farm, Urbana, Ohio. On April 2Jj., 1950, 59 hens and 12 cock pheasants were placed in the enclosure, and on March 3* 1951* 120 hens and 15 cocks were stocked. During both seasons, the birds were trans­ ported to the study area, marked, and released into the enclosure on the same day. Before release, the birds, which had been brailed at the Game Faim, were individually marked with Taber-type plastic - l U - markers (Taber, 19k9a.) and also with combinations of colored, anodized' aluminum leg bands (Fig. U and 5)»

Although there was abundant vegetative growth in the study en­ closure, food, water, calcium, and granite grit were provided during both seasons. Water was made available to the brood stock by use of poultry-type fountain waterers, and oyster shell and granite grit were provided along with a whole grain feed mixture of 70 percent corn,

20 percent wheat, and 10 percent oats. The food, the oyster shell, and the grit were distributed on the bare areas throughout the en­ closure several times weekly or as needed.

Supplementing the rations of the brood stock may not have been necessary; however, improper diet resulting in reduced egg laying capacity would have introduced a serious variable into the study.

Observations both years indicated that the brood stock drank water copiously and fed heavily upon the grain mixture. Utilization of the grit was difficult to judge, but the oyster shell seemed to be used considerably.

The remaining brood stock was trapped in the area and released outside the enclosure during the third week of August, 1950, and during the last week of October, 1951*

2. Observations of Brood Stock

Observations were made almost daily during both years from the day the enclosure was stocked until about the end of August. Obser­ vations of breeding behavior usually were made during the early and late daylight hours from either of two 16-foot high wooden towers, one situated at the east end and the other at the west end of the -15-

Figure u«

Attaching Plastic Marker to Hen Before Release -16-

Figure 5*

Hen with Plastic Markers and Leg Bands -17- enclosure (Fig. 3). Excellent observation was afforded the observer from these vantage points, especially with the aid of binoculars and a mounted spotting scope. Of course, observations also were made while on foot, working in the area.

3* Location of Nests

Nests and nesting hens were located by periodic searching of the cover strips (about 7-day intervals). Since the hens were marked with brightly colored plastic markers, they were not difficult to detect

(Fig. 6 ). When nests were found, their approximate locations in strips were plotted on a small scale map of the area (Fig. 2), and to aid in re-locating the nests more quickly, small metal stakes were driven into the ground at the edge of the nearest bare strip. Once nests were located, they were checked daily for any change in clutch sizes and for the identification of hens. If hens were not associated with nests within 10 days, the eggs were removed, the nests were broken up, and the cover adjacent to nests was cut down. This was done to prevent broody hens from adopting clutches.

U. Aging of Clutches and the Assignment of Nests to

Categories of Incubation

When an incubated clutch was found and the hen identified, the length of incubation was determined by aging embryos (Dustman, 19^9)

(Fig. 7)* Eggs removed from nests for aging were replaced by other eggs. To investigate two of the objectives of this study(C and D, pages $ and 6 ), it was necessary to disrupt hens that had been in­ cubating for various lengths of time. Therefore, after clutches had been aged, nests were assigned as randomly as possible to categories -18-

Figure 6.

Incubating Hen -19-

Figure 7*

Aging Embryos - 2 0 - of incubation by using a table of random numbers (Snedecor, 19U6).

Five categories of incubation were established arbitrarily at 1-3,

6-8, 12-lU, 18-20, and 21-23 days of incubation. After clutches had been incubated the desired number of days, the hens were disrupted by the investigator. When hens were found renestiag, the same procedure of aging, assignment to categories of incubation, and disruption was followed.

Disruption of Hens

When hens were disrupted, the procedure was as follows: a ratchet noise maker was whirled with one hand while hens were vigorously swept from nests with a broom manipulated with the other hand, and hens were then chased from the nest area. The noise maker and broom were used in an effort to produce at least a strange if not frightening effect on the hens (Fig. 8).

Once hens had been chased from the vicinity, the eggs were taken from the nests and vegetation was cut down within a radius of three feet of the nests. The nests were scattered and a few of the eggs were broken and strewn about the site. The disrupted nests resembled ones that might be seen in mowed hay fields (Fig. 9). Figure 8.

Hen Disruption Procedure -22-

Figure 9*

Site of Disrupted Nest III. Results

A. Behavior of Brood Stock in Relation to the Enclosure Area

The brood stock was placed in the study enclosure on April 2kj

1950. For about ten days following the date of release, the birds tended to flock in the fence corners and along the fence lines, ven­ turing into the cover strips only at night to roost. The cover was about I4. inches high when the birds were released. By May 3* the cover varied between it and 6 inches in height and the birds began to disperse throughout the area.

The release of the brood stock in 195>1 was made on March 3* As observed the previous year, the birds flocked in the field corners and dispersed along the fences. Roosting occurred in the cover strips which afforded poor cover. The brush which had been placed in the enclosure as escape cover (see discussion of cover) was used consid­ erably by the birds during the diurnal hours; however, the majority continued to roost in the cover strips. The new vegetative growth in the cover strips was about 6 inches high by the third week of April, and the birds began to disperse throughout the area at this time.

As the natural cover increased in height, the brood stock utilized it to a greater degree during both seasons. The shifting of activity from the proximity of the fence and fence comers to the cover strips was a gradual process.

B. Breeding Behavior

Nestler (19U6) reported that the presence of fencing would con­ stitute an unnatural barrier that would prevent animals from behaving in a strictly normal manner in enclosure studies. Regardless of the

-23- -214- fact that birds were brailed, confined, and cover conditions were probably atypical, the breeding behavior observed during the course of this study was similar to that reported for wild populations, and the various types of breeding behavior noted, such as crowing, courtship and mating, display, and fighting was very similar to that described by Taber (19U9b). Antagonism between cocks and the attraction between cocks and hens were well developed when birds were released in the enclosure in 19!?0. Some of the hens were in the egg-laying stage and cocks were observed crowing, displaying, fighting, and copulating with hens shortly after the date of release. Breeding behavior was first noted in 1951 about the third week of March.

1. Territorialism

There is general agreement that the pheasant is territorial.

The areas defended by cocks have been called territories or crowing areas and the terms have been used synonymously (Randall, 19U0);

(Baskett, 19U7); (Taber, 19U9b). Various authors have reported that territories appear as rather defintely delineated units (Kozlowa,

19U7); (Wight, in McAtee et al., 19U5)j (Randall, 19U0)j (Shick, 1952).

Other observers, however, have reported that territories are not always clearly defined (Leedy and Hicks, in McAtee e_t al•, 19b$)}

(Ruffing, 1952)j (Baskett, 19U7)- Dustman (19U9) reported that some, but not all territories remained as distinct entities throughout

April and May. Territory boundaries in the writer1s study were determined by observing crowing sites and points of conflict between cocks. Cocks establishing territories earliest usually ranged over large areas, but as other cocks became territorial, these areas were -25- reduced, and became rather sharply defined and stable. Once all territories had become established, they appeared as rather definitely delineated units.

a. Territorial Conflict

According to Wight (in McAtee et al., 19H5)> the basis for fight­ ing between cocks was the protection of crowing areas and/or the possession of hens. Baskett (19U7) reported that most fighting appeared to be in defense of land area and not of females, but that in a few instances it may have been over hens. According to Noble

(1939)* territory is defined as any defended area. Observations by the writer also indicated that fighting by territorial cocks was the defense of a territorial area (Fig. 10).

Allee (19U2) found that animals, including birds, fought best when defending their home territories. This was observed to be the case in the writer's study, where in no instance was a territorial cock subdued when fighting within the limits of his territory. Some of the fighting that occurred when cocks encountered one another at territorial boundaries probably was a result of their aggressive behavior and not always a purely defensive response.

b. Aggressiveness and Dominance

With the development of breeding behavior, some cocks soon appeared more aggressive and subsequently dominant to others. These birds, called aggressive cocks in this discussion, were much different in appearance and behavior than non-aggressive cocks. The wattles of aggressive cocks were swollen most of the time, their body feathers were held out, giving the impression of bulk, and quite often the ear -26-

Figure 10.

Cocks Fighting -27- tufts were erected. Aggressive cocks made frequent intimidation displays to other cocks and engaged in much courtship display. All cocks observed to be aggressive eventually crowed and established territories.

Collias and Taber (1951) observed aggressive-submissive inters­ ections between pheasants and reported evidence for the existence of a dominance hierarchy. They reported a strong association between the establishment of crowing territories and ability to dominate other cocks. Some degree of dominance hierarchy is believed to have existed in the writer*s study. All territorial cocks were dominant over non­ territorial cocks. Some cocks became territorial later than others, and until they had established their territories, they were dominated by territorial cocks. Once all territories had been established, territorial cocks were equally successful in defending their territor­ ies against all cocks. Thus, no dominance hierarchy was observed among the territorial cocks.

c . Territorial Establishment

1. Time of Establishment

Initial territorial establishment occurred later in 1950 than in

1 9 5 1 , probably because the birds were placed in the enclosure at a later date. There also was considerable variation in the dates of territorial establishment each year. The earliest territory was established on May I4., 1950, and the remaining two were established on May 10. In 1951, the earliest territory was established on April

3, and the latest on May 16, a time lapse of almost a month and a half

(Table 1). Table 1.

Dates of Establishment and Sizes of Territories, and Dates

of Establishment and Sizes of Harems, 1950-1951

Dates of Territorial Territorial Sizes of Dates of Harem Number of Cocks Establishment Territories (Acres) Establishment Hens in Harems 1950 1951 1950 1951 1950 1951 1950 1951 1950 1951

h E 5/a U/3 3.9 1.2 5/a a/5 25 17

7 U 5/io a/5 1.6 2. a 5/io a /ia 12 20

YJ 5/io a/29 1.9 1.7 5/io a/29 ia 23

C 5/8 1.3 5/8 10 vr\ O C P 5/8 0.8 7

u 5/16 0.1- 5/16 6 -29- 2. Number and Sizes of Territories

Territory sizes were estimated on the basis of the area defended by cocks, and territorial sizes are presented in table 1. The config­ uration and relative size of each territory for each year are presented in figures 11 and 12. Twelve cocks were stocked in 1950, and three became territorial. Fifteen cocks were stocked in 19$1* and six be­ came territorial. One cock died in 1950 and two died in 1951* but none of these had been territorial,

3» Fluctuations in the Sizes of Territories

Baskett (19U7) and Taber (l9U9b) were of the opinion that territories were very plastic in nature and subject to frequent re­ adjustment. Taber reported further that the size and shape of terri­ tories were sometimes modified by environmental changes, such as the extension of the daily cruising radius of hens and pressure from adjacent territorial cocks. Muhlbach (195U) reported that with an abundance of suitable cover and feeding areas which remain stable in quality and position, a cock has "no apparent need to expand his territory." The writer observed no gross fluctuations in territory size in the present study except when one cock in 1951 deserted his territory and another cock then included it in his territory. Homo­ geneity of cover and the plentiful distribution of food and water throughout the area are factors that may account for the stable terri­ tory sizes observed in the study enclosure.

I4. Territorial Requirements

Wight (in McAtee et al., 19U5) wrote that the extent and shape of crowing areas were determined by the composition, density and -30 -

Figure 11.

Cock Territories, 19^0

7 Cock

U Cock

T Cock -31-

Figure 12.

Cock Territories, 1951

U Cock P Cock

U Cock C Cock

E Cook J Cock -32- arrangement of cover, and that a patch of either brush or woods was an essential part of the cover within a crowing area, although during the latter part of June, hayfields provided sufficient cover. Sharp and McClure (in McAtee et al., 19U5) reported that territories often have as their hubs, thickets of plum, willow, c'nokecherry, or rose.

The inclusion of an isolated patch of woody cover as part of a cock’s territory was reported also by Dustman (l9k9); this author, however, pointed out that shrubby or woody cover did not occur in some of the territorial areas. Shick (19£2) reported that crowing areas were selected for proximity to protective cover in a situation where nesting cover and food were well dispersed. The results of the writer* s study indicate that shrubby or woody cover was not a necessary component of a territorial area.

Various investigators have discussed the importance of open ground as part of a territory. Taber (I9i#b) reported that the bulk of sexual activity occurred during the morning and evening feeding periods, which were spent on, or at the edge of, relatively open ground. Muhlbach

(19$U) also reported the use of open areas during the morning and evening feeding periods. The findings of the writer1s study were similar to those of Taber's and Muhlbach's, the open ground in this instance being the care earth.

5* Cessation of Territorialjsm

Crowing and territorial behavior were at a high level throughout the main portion of the breeding seasons, and the cessation of these activities was a gradual process. Crowing had practically ceased by the middle of July in both years; territorialism ended by August 1, -33- 1950, and for most of the cocks by August 15, 195l»

2. Non-Territorial Gocks

Cocks that do not establish territories are called non-terri­ torial or submissive cocks. They were never observed crowing, and in only one instance was one observed fighting. Their secondary sexual characteristics were poorly developed; however, they did mate with hens. Submissive cocks were observed displaying only to hens and other submissive cocks of low dominance. A territorial cock would usually not tolerate the presence of a submissive cock in his territory or with his harem. There were occasions, however, when a territorial cock gave little heed to a non-territorial cock. Submissive cocks skulked throughout the enclosure area and were harassed only when encountered by a territorial cock. These observations, in the main, were similar to those made of a wild population by Taber (19ii9b), who found that non-territorial cocks had the following characteristics:

"(1) they were never seen to crow; (2) their wattles were always small unless they were actually in close contact with hens (a rare event);

(3) they did not cluck; (iu) they did not fight; (5) they did not court

(display to) hens after mid-April."

There are few references in the literature about non-territorial cocks; however, Wight (in McAtee £b al., 19U5) probably based the following statement on observations of submissive cocks: "If a male is entirely vanquished in his quest for an area, he usually moves out completely, and becomes a wanderer, and is driven from place to place as he enters the territories of other birds." Ball (1950) made crowing cock counts on Pelee Island in 19U8 and did not observe any -3 li­

no n-c rowers . He states, however, that there were certainly soae non­

territorial cocks that due to position could have been missed on the

crowing counts.

In the writer's study, 9 of 12 cocks in 1950, and 9 of 15 cocks

in 1951 were non-territorial, and, in enclosure studies conducted

subsequently by others, a high degree of non-territoriality was also

observed. The results of these studies are as follows: Smith (1953)

reported 9 of 15 cocks in one area and 10 of 15 in another as non-

territorialj Kessler (1953) found lU of 3h cocks non-territorial;

Semones (1955) reported 10 of 30 cocks non-territorial; and Muhlbach

(195U) found 8 of 16 cocks to be non-territorial.

Non-territoriality may be associated with the unnatural confine­ ment of cocks in the study areas and this high incidence of submissive­

ness may be atypical of behavior in the wild. Non-territorial cocks,

however, may be more prevalent in the wild than has been generally be­

lieved, but are seldom seen because of their furtive behavior.

Furthermore, most observers have probably given closer attention to

the territorial cocks. The results of the close scrutiny by Taber

(l9U9b) of a wild population may be an indication of the prevalence of wild non-territorial cocks. During the season of 19U8, Taber observed

18 territorial, 8 non-territorial, and 3 cocks of doubtful territorial

status. The proportion of non-territorial cocks he observed is not

too different from that which occurred in the various enclosure

studies cited above.

Muhlbach (195U) discussed the high incidence of non-territorial

cocks observed in his study and concluded that it was a result of the -35- high density of birds and the intensive land use in the area. Taber

(19u9b) reported that fewer non-territorial cocks seemed to occur in

the thinner populations of the uplands as compared to the higher pop­

ulations at the marsh edge. In the writer's opinion, cock densities

in the enclosure areas could have been one of the reasons for the high

incidence of non-territoriality. However, Collias and Taber (1951)

have reported that: "The association between high rank in the winter

cock hierarchy and ability to establish a territory during the breed­

ing season is suggestive of the true nature of the basis of breeding

success." Thus, dominance-submissive interactions observed in the

enclosure studies probably were, to a great degree, a continuation of behavioral patterns established before release. The explanation for

cocks becoming either dominant or submissive may be found in the work

of Allee (l9i|2), who reported that dominance-subordinate social patterns of animals may be influenced by environmental factors and may have their foundation in heredity, the physiological state of

individuals, and psychological factors.

3. Harem Formation

Harems were formed at the time of territorial establishment or

shortly thereafter during both seasons (Table 1). During 1950, 51

hens were associated with harems, and in 195l> 83 hens were in harems.

One hen in 1950, and 12 in 195l> were not commonly associated with

any one territorial cock, and are not included in the above figures,

a. Number and Sizes of Harems

Three harems were formed in 1950, and six in 195l» Considerable

differences also were observed in harem sizes both seasons. As seen -36- in table 2, harem sizes varied between 12 and 25 hens in 1950, and between 6 and 23 hens in 1951. The identities of hens comprising the harems of territorial cocks were ascertained by observations of breed­ ing activity during the early morning and early evening hours.

Although harem counts for any one day usually did not represent all of the hens associated with any one harem, after hens were observed repeatedly with a particular cock, they were assigned to that cock's harem (Fig. 13).

b. Stability of Harem Composition

□nee hens appeared to have definitely associatedthemselves with specific harems, they seldom shifted to another. Even after hens had been disrupted from nests, they were observed to rejoin their former harems. During both seasons, the breaking up of harems was a gradual process. In 195>0, flocking had occurred by the third week in July, but in 1951* although harem composition appeared to break down con­ siderably during the last two weeks of July, some hens were observed to remain in the company of a few of the territorial cocks throughout

August and September. Harem composition was probably maintained for a longer period of time in this study, as compared to observations of wild populations, since most of the hens were disrupted from nestings and rejoined their former harems.

c* Dominance Hierarchy of Hens

Collias and Taber (1951) presented evidence for the occurrence of a dominance hierarchy in the population of wild hen pheasants observed by them. They found that early aggressive-submissive inter­ actions between hens consisted of only pecking, threatening, or Table 2.

Harem Composition and Degree of Initial Nesting, 19$0-1951

1950

Territorial No. Hens No. Hens in No. of Non- % of Hens Cocks_____ In Harems Harems Nesting Nesting Hens Nesting

k 25 21 h 8U

W-7 12 12 0 100

R-Y 1/4 1U 0 100

Totals 51 hi k 92

1951

J 23 21 2 91

k 20 20 0 100

E 17 17 0 100

C 10 10 0 100

P 7 5 2 71

u 6 6 0 100

Totals 33 79 h 95 -38-

W&M$,

Figure 13.

Territorial Gock and Part of Harem -39- chasing, but that as the breeding season advanced to the point where

harems began to be established, antagonism between females manifested

itself in fighting or display. Antagonism between hens was reported also by Taber (19U9b), who stated that fighting between hens and dis­ play of one hen to another was concurrent with harem formation.

Dustman (19U9) observed fighting between hens and stated that hens fought in a fashion similar to that of cocks.

Antagonism between hens was observed in the present study, and though most instances of antagonism were observed at the height of breeding activity during the month of May, it was occasionally seen throughout the season, with a resurgence of antagonism about the middle of July. Since hens usually rejoined harems, after having been disrupted from initial or subsequent nesting, more antagonism than usual probably was observed in this study.

U. Territory and Harem Relationships

Smith (19£3) reported that cocks establishing territories early in the season acquired the largest harems and may have had slightly larger territories. However, Muhlbach (195U) found that territory size was generally independent of harem size, and Kessler (1953) who analyzed his results statistically, found no significant relationship between harem sizes and the size of territories.

In the present study the largest territories and harems were those established the earliest during a season. Since territory and harem formation occurred at nearly the same time, the cocks having the largest territories acquired the largest harems (Table l). The aggressiveness of cocks probably was the most important factor -1+0- influencing the sizes of territories and harems.

Inter-Specific Strife

Einarsen (191*5) reported that territorial competition among cocks probably adversely affected breeding activity on Protection Island when the pheasant population reached about five birds per acre. As far as could be discerned, competition among cocks did not adversely affect breeding and nesting activity in the present study in 1950, with a breeding population of 9 birds per acre, or in 1951, with 11*. 1* birds per acre. Of course, the "edge factor" may account for this lack of intolerance, since the arrangement of the cover strips in the research area resulted in a high proportion of edge to the area in­ volved. Another major difference between the populations observed by

Einarsen and those observed by the writer was that of sex ratios

(number of cocks per 100 hens). When intolerance was observed by

Einarsen, sex ratios on Protection Island were 130 cocks per 100 hens in the spring of 191+1, and 150 cocks the following spring, whereas in the present study, sex ratios were considerably lower, i.e., 20 cocks per 100 hens in 1950 and 15 cocks per 100 hens in 1951* The intoler­ ance observed by Einarsen probably was due in part to the high sex ratios which prevailed in the population on Protection Island.

^ * Egg Laying, Nesting, and Incubation

Some of the hens in 1950 were in a laying condition at the time of their release on April 21*. Eggs were found in the crates used to transport the birds to the area and in the enclosure on successive days subsequent to stocking. In 1951* the birds were introduced into the enclosure on March 3, before the onset of egg laying, and the - i a - first egg was not found until April 8. The chronology of the laying behavior of hens both seasons was generally similar to that described by Buss et_ al. (1951) and Stokes (195U), i.e., the laying of single

eggs (dropped eggs) apparently at random throughout the enclosure area

(not laid in nests), the laying of eggs in dump nests (more than one hen laying in the same nest), the laying in nests which were abandoned, and finally, the laying in nests of eggs which were eventually in­ cubated (Fig. li;, 15, and 16).

Birds were stocked too late in 1950 for the observer to check on the extent of egg dropping, but this was possible in 1951* During this year, 22k dropped eggs had been found by May 3, 1^1 between May 3 and

May ll;, and 1U5 from May llj. to the end of the season. This distribu­ tion of dropped eggs during the laying season is in agreement with the findings of Muhlbach (195U), who reported that random dropping of

single eggs was much reduced after mid-May.

1. Hens Available for Nesting

Initial nesting occurred shortly following stocking in 1950, and

59 hens were considered available for nesting. At the time of estab­

lishment of initial nests in 1951, predation, for the most part, had resulted in a reduction of the breeding stock to 99 hens. Since the observer disrupted most of the nesting hens both seasons, nearly all were available for possible renestings. The numbers of hens consid­

ered available for initial nesting and renesting are shown in table

3* As seen in the table, most of the hens available for initial nest­

ing both years, nested; however, nesting percentages were higher in

1951 for initial nests and renests. The lower percentageof nesting Figure ll|.

Dropped Eggs Figure l£.

Dump Nest in Clump of Red Clover Figure 16*

Incubated Nest -U5-

> Table 3»

Nesting Data, 1950-1951

1950 1951

Number of hens available for initial nestings 59 99 Number of hens associated vrith an initial nest h8 91 Percent of hens nesting initially . 81% 92% Number of initial nests assigned to categories of incubation and disrupted • la 80 Number of initial nests incubated and deserted 1-iBHBc I4. Number of initial nests unincubated and deserted 2 2 Number of initial nests incubated but not disrupted^-# 2 1 Number of initial nests hatching 3 k*

Number of hens available for second nestings Uh 88** Number of hens associated with a second nest 16 59** Percent of hens nesting twice 36% 67$ Number of second nests assigned to categories of incubation and disrupted 12 51 Number of second nests incubated and deserted 2 1 Number of second nests unincubated and deserted 0 1 Number of second nests incubated but not disrupt edtf-is-K- 2 2 Number of second nests hatching 0 h

Number of hens available for third nestings 15 55 Number of hens associated with a third nest 2 8 Percent of hens nesting a third time 13% lh% Number of third nests assigned to categories of incubation and disrupted 2 7 Number of third nests incubated and deserted 0 0 Number of third nests unincubated and deserted 0 0 Number of third nests incubated but not disrupt ed-JBBt- 0 0 Number of third nests hatching 0 1

Number of hens associated with a fourth nest 0 0

One hen lost brood and became available for renesting. •a-a- Includes one hen which hatched four young from an initial nest and was found later on a second nest. -JBB4- Birds killed, or unable to determine length of incubation, or nests disrupted at wrong stage of incubation. -JBBHtAssigned to a category of incubation. -U6- in 1950 might be due, in part, to the late stocking that year. Eleven hens in 1950, and eight in 1951, were not associated with a nest of any type.

2. Nest Establishment and Incubation

Determining the establishment dates of unincubated clutches is sometimes difficult, but all clutches of both seasons were aged as accurately as possible. The dates of establishment were determined by allowing 1.2 days for the laying of each egg in clutches, and if clutches had been incubated, by also adding the number of days in­ cubation had occurred. The stage of incubation was determined by aging embryos (Dustman, 19U9). Establishment data and the number of nests incubated for both years are presented in table U. During both seasons, the height of nest establishment occurred in May and the greatest number of clutches were incubated in June,

a. Number of Nests Per Hen

Bus et al. (1951) postulated that wild hens probably desert one or two nests before laying a clutch and incubating it. This laying behavior would mean that hens, on the average:, lay two to three clutches each. The results of the present study showed that during 1950, 59 hens laid 92 clutches (renests excepted), or 1.5 nests per hen. In

1951, 99 hens laid 162 clutches (renests excepted), or 1.6 nests per hen. Kozicky and Hendrickson (1951) reported on the nesting of hens over a 5-year period in Iowa, and even when using all nests, which no doubt included some renests, found an average of only 0.9 to 1.6 nests per female. The hen population and nest figures presented by

Yeager et al. (1951) have been used to calculate the number of nests -117-

Table 1+.

Nest Establishment and Incubation, All Nests, 1950-1951

No. Nests No. of Nests Percent of Weekly Established Incubated Nests Incubated Periods 1950 1951 1950 1951 1950 1951

April 22-23 3 9 2 1 67 li

April 29-May 5 3 lU 0 2 0 11+

May 6-12 9 18 b 11 33 61

13-19 16 29 6 15 38 52

20-26 22 UO 12 28 5U 70

May 27-June 2 lb 18 8 15 57 83

June 3-9 9 15 9 15 100 100

10-16 13 21+ 9 20 69 83

17-23 k 23 2 20 50 87

2U-30 b 16 b 13 100 81

July 1-7 7 13 b 8 57 62

8-lU 2 7 l 6 50 86

15-21 1 1 l 0 100 0

22-28 0 2 0 1 - 50

July 29-Aug. U 1 0 1 0 100 -

Totals 108 229 63 155 58$ 68$ -1+8- per hen for a 3-year period in a Colorado area, and the nesting, renests included, varied between 1 .1+ and 1.6 nests per hen.

The birds observed in this study and the studies mentioned above did not lay so many clutches as those hens observed by Buss et al.

(1951)• However, due to the high breeding density in the present study, eggs which might normally have been laid in early individual nesting attempts possibly were laid in communal dump nests.

b. Nest Types and Clutch Sizes

In this study, any site showing some sign of nestconstruction and containing one or more eggs was considered a nest. The nest types encountered were dump nests, abandoned nesting attempts, and what are called bona fide nests that were incubated. In some instances, dump nests also were incubated. Considerable variation in the sizes of clutches of the various nest types was observed as follows:

Nest Types Range in Clutch Sizes 195>0 1951

Unattached nests* 2-51 2-1+6 Initial nests 1-25 5-33 Second nests 3-10 2-21 Third nests 6-7 3-15

*Dump nests and abandoned nesting attempts.

Baskett (191+7)* Hamerstrom (1936), Dustman (19U9)* and Stokes

(1951+) have reported finding dump nests containing high numbers of eggs, and Stokes suggested that communal laying probably rises with breeding density. Many large clutches were observed during this study, the largest being a compound dump nest of 51 eggs (Fig. 17)* and more dump nests were observed in 1951 when the breeding density was higher. -U9-

Figure 17•

Compound Dump Nest -50-

The mean numbers of eggs for the various nest types observed in

the present study are given in table 5* The clutch sizes of renests

are smaller than those of initial nests. Various authors also have reported progressive decreases in the clutch sizes of pheasants and

other species as the nesting season advances (Hamerstrom, 1936; 1939;

Dustman, 19U9; Lack, 19U7a; Randall, 19U0; Bennett, 1938; Edminster,

19L7; Stokes, 195hi and Sowls, 19k9} 1955)* Many of these investi­

gators have attributed the decrease in clutch sizes to renesting;

however, the work of Sowls is the only known instance where marked birds were used. Sowls found the number of eggs in first clutches to

be statistically greater than the number of eggs in renests (the

mean difference between initial and second clutches being 2 .0 ), but

that the difference was not great enough to distinguish first clutches

from renests.

The results of the present study also reveal that initial clutch

size is significantly greater than the clutch size of second nests.

In 1950, the mean difference between the clutch sizes of the first

and second nesting attempts of 10 hens was 2.8. The data were treated

as unpaired, and the U-test of Mann and Whitney (19^7) was used in the

statistical analysis. The results revealed a very significant

difference between the clutch sizes of first and second nesting

attempts (observed u = 83)• Under the null hypothesis such an ob­

served value would occur with less than one-percent probability—

U - 81. The initial and second clutches of 3U hens nesting in

1951 were also compared and tested in the same manner. The mean

difference between the clutch sizes of the first and second nests -51-

Table 5.

Mean Number of Eggs for Various Types of Nests, 1950-1951

19^0 19$1 Nest No. of No. of Mean No. No. of No. of Mean No. Types Nests Eggs Eggs Nests Eggs Eggs

All nests 108 1161 10.8 229 2979 13.0

Incubated nests 63 613 9-7 155 1316 11.7

Initial nests U8 b99 10. k 91 111+1+ 12.6

Second nests 16 120 7.5 59 612 10.1+

Third nests 2 13 6.5 8 82 10.3

Unattached nests U2 529 12.6 71 lll+l 16.0 -52-

of 3U hens was 2.2!. The result of the statistical analysis again

shows that the clutch size of a first nest is larger than that of

a second nest (observed S = 385} ^ Q1 ” 388).

Although the number of eggs in initial nests is statistically greater than those in second nests, the evidence indicates that initial nests cannot be distinguished from renests on the basis of

clutch size. The writer also found that renests could not be

distinguished from initial nests by type of construction, amount of

down, location of nests, and to some degree, by time of season.

The clutch sizes of the initial nests and renests used in the

analyses are shown in table 6 . The eggs in each pair of first and

second nests used in the analysis were believed to have been laid by only the one hen associated with the pair of nests. The clutches

of all renesting hens could not be used in the analyses because some clutches were adopted and others were the result of the laying

activity of more than one hen.

The smaller clutch sizes of renestings might account for the

seasonal decreases reported by many authors. However, Stokes (195k)

found a progressive decrease in clutch sizes as the nesting season

advanced, with little renesting occurring. This suggests that a

decrease in clutch size may occur independent of renesting. The

observations of Dustman (19U9) lend further support to the idea. He

reported that'it was doubtful that renesting alone could have been

entirely responsible for the smaller clutches observed by him during

two nesting seasons characterized by heavy rains and flooding. He

suggested the possibility that physiological changes due to the -53-

Table 6.

Clutch Sizes of First Nests and Renests, 1950-1951

Hen No. Eggs in No. Eggs in Year Number First Nest Second Nest 1950 1 8 7 2 12 10 3 8 7 k 9 9 5 15 9 6 9 6 7 9 5 8 10 8 9 8 3 10 11 7 1951 1 8 6 2 9 9 3 9 7 h 10 11 5 Ik 15 6 10 10 7 11 13 8 7 12 9 13 Ik 10 9 8 11 16 9 12 8 lk 13 19 5 1U 8 8 15 21 9 16 9 12 17 9 7 18 10 8 19 12 10 20 13 6 21 9 8 22 12 7 23 18 8 2k 13 7 25 10 2 26 15 h 27 7 5 28 7 5 29 13 9 30 9 11 31 11 m 32 li; 10 33 11 10 3U 7 12 -5U- adverse weather conditions might have affected the reproductive activity of laying hens. Muhlbach (195U) concluded that the season­ al reduction in clutch sizes observed by him involved primarily the seasonal factor alone.

There is evidence that clutch sizes decrease with the advance­ ment of nesting seasons. The seasonal decrease in clutch sizes of both initial and renests is no doubt affected by prior laying activity, as well as by the influence of seasonal and weather factors on the reproductive physiology of hens. The over-all productivity of a species such as the pheasant would be seriously handicapped during a season characterized by considerable renesting with smaller clutches as the result, plus factors operating independently of renesting to further reduce clutch sizes.

3* Egg Production and Fertility

Records were kept for all eggs found for both years, but complete records were not obtained in 1950 because hens had been laying before being placed in the area. Although production was higher in 1951* incomplete data in 1950 make a fair comparison impossible. The average of 32.6 eggs per hen in 1951 compares closely to the figure of 3k reported by Buss et al. (1951) as the average number of eggs laid by 11 hens confined in large pens. Egg production data are summarized in table 7 *

Data on egg fertility were not obtained for dropped eggs during the 1 9 5 0 season; however, 89 percent of 2 3 1 eggs from U5 initial nests contained embryos, and 83 percent of 63 eggs from 15 second nests con­ tained embryos. Dropped eggs collected between April 8 and May U* 1951* -55- were incubated and embryos developed in 83 percent of them. Embryos were found in 95 percent of 1,011 eggs in 87 initial nests; 89 percent of 591 eggs in 57 second nests; and 88 percent of 82 eggs in 8 third nests. Fertility percentages are probably conservative because some embryos die early in incubation and cannot be distinguished from infertile eggs. Over-all fertility was higher in 1951; however, fertility decreased for second nests both years, i.e., 89 to 83 percent in 1950; 95 to 89 percent in 1 9 51*

Table 7 .

Egg Production, 1950-1951

1950 1951

Number of hens present in area at onset of egg laying 59 107

Total number of eggs found 1268 3U89

Number of dropped eggs found 107 510

Mean number of eggs per hen 21.5 32.6

U. Time and Duration of the Nesting Period

Most workers report pheasant nest establishment as occurring from early April to late July (Lyon, 1952). During both years of this study, when all nests were considered, the nesting span was from late April to late July (Fig. 18). However, where most other workers were unable to distinguish initial nests from renests, this was possible in the present study. Accordingly, data are presented showing the periods of nesting for initial, second, and third nests (Fig. 18). Figure 18.

Periods of Nest Establishment, 1950-1951 (Based Upon Incubated Nests)

1950

U—21l 6=15 Initial Nests

6-6 Second Nests

7-U 1 - 9 Third Nests □ - 9 5 -

1951

U-25 6-21 Initial Nests

5-*a 7-22 Second Nests

6-2£ 7-13 Third Nests

1------1— —,------,------p _ il-15 5-1 5-15 6-1 6-15 7-1 7-15 8-1 Bate of Season -57-

Initial nests were not established after June 21 either year; however, at least some second nests were established relatively early in the seasons. Investigators have been too prone to arbitrarily call early nests first nest, and late nests renests (Shick, 1952;

Hiatt and Fisher, 19i+7) • The writer is of the opinion that many so- called first nests are actually early renestings, and in fewer instances, nests that have been designated as renests, are actually late first nests. Detailed nest establishment data for both years for all nests observed are presented in table 8 . The peak of nest establishment occurred during the same weekly period both years

(May 20-26), and median nest establishment occurred on about the same date both years (May 29, 1950; May 28, 1951)* The midpoint of potential hatching would have been June 29, 1950, and June 25, 1951*

D. Behavior of Nesting Hens

1. Behavior of Incubating Hens

During the course of this study, nesting hens were located and identified and eggs were frequently removed from beneath them. While engaged in these activities, various aspects of incubation behavior were noted. Leopold (1933) gives "dawn and i;:00 p.m." as the time when incubating pheasants leave their nests or take "rest periods", while Muhlbach (195U) stated that hens usually left their nests for brief periods of feeding early in the morning and in the evening.

The writer, however, did not find it possible to predict with accuracy when any one hen would be away from her nest. Baskett (19i+7) also was unable to determine when pheasant hens would be off their nests. Table 8.

Nest Establishment Data* All Nests, 1950-1951

No. Nests Percent Cumulative Weekly Established of Total Percentage Periods 1950 1951 1950 1951 1950 1951 April 22-28 3 9 3 U 3 h

April 29-May 5 3 1U 3 6 6 10

May 6-12 9 18 8 8 m 13

13-19 16 29 15 13 29 31

20-26 22 ko 20 17 k9 U8

May 27-June 2 1U 18 13 8 62 56

June 3-9 9 15 8 7 70 63

10-16 13 2U 12 10 82 73

17-23 1+ 23 1+ 10 86 83

2U-30 u 16 h 7 90 90

July 1-7 8 13 1 6 97 96

8-11+ 1 7 l 3 98 99

15-21 1 1 l - 99 -

22-28 0 2 - 1 - 100

July 29-Aug. 1+ 1 0 l - 100 -

Totals 108 229 100 100 --

Note: 5U nests established by 5/29/50, or 50 percent 1,16 nests established by 5/28/51, or 50.6 percent. -59- During the initial phases of this study, when eggs were removed

from clutches to age the embryos, an effort was made to take eggs when the hens were absent. Since incubating hens were not away from

nests at any predictable time, the observer was forced to take eggs

from beneath them. This was not done initially because of the chance

that desertion might have resulted; however, once hens were found to be very tolerant to molestation, eggs were removed from beneath them

as a customary procedure.

When eggs were removed, most hens offered no resistance and moved off the nest and did not return until the observer had left

the vicinity of the nesting site. However, some hens would remain on

the nest and a few of these hens were pugnacious. According to

Muhlbach (195k)* hens became increasingly pugnacious toward intrud­

ers during the latter half of incubation. In the writer's study, most of the pugnacious hens were encountered during the later stages

of incubation, but some also were found during the earlier stages,

some as early as three days of incubation.

When nesting hens were discovered during nest searches, they would flush less readily if the searcher did not show by a change in

behavior that he was aware of them. The cessation of whistling, walking, singing, or talking would seem, at times, to be the stimulus

for the flushing of hens. Similar behavior was observed by Baskett

(19U7)« Several hens did not flush from nests even after having been

stepped upon accidentally during nest searches. Upon examination

later, the hens appeared to be unhurt. -60-

In this study, good nesting records for each hen were important.

Therefore, proper technique in nest searching and inspection was necessary. If improper methods had resulted in considerable desertion at the time of nest discovery, identification of hens could not have been made in all cases, and data on hens would have been incomplete.

2. Behavior of Disrupted Hens

During this study a total of 193 incubated nests were disrupted

(Table 3)» See page 20 for the method of disruption. Different behavioral responses were observed when hens were disrupted. The majority of the hens quickly left the nest site with no defense behavior being manifested. Some of the hens, however, became pugnac­ ious toward the observer and resisted his attempts to dislodge them from nests. Pugnaciousness was characterized by one or more of the following responses: displaying, hissing and chirping, and rushes toward the intruder (Fig. 19)* The response of hen R-0 is a good example of extreme pugnacity. After 6 to 8 seconds of disruption procedure, the hen was driven from the nest and chased from the nest­ ing area. As the observer was returning to the nesting site, the hen also returned and had to be driven away again, as she displayed, hissed, and rushed the observer. Several minutes later, while the observer was working at the nest site, the hen approached again, within 1; feet of the nest, and repeated the pugnacious behavior, making four rushes at the observer. After being driven away for the third time, she did not return while the observer was at the nest site- -61-

Figure 19.

Display of Pugnacious Hen -62-

3* Clutch Usurpation and Adoption

One instance of clutch usurpation and several instances of clutch adoption were observed during this study. Usurpation is the taking over of another hen’s clutch by a disrupted hen; adoption is the taking over by a disrupted hen of a clutch with which no hens have been assoc­ iated. The usurping or adopting hen may or may not lay additional eggs in a nest.

The one instance of nest usurpation was observed in 1951 when hen Y-3 was disrupted from an initial nest on June 7 after seven days of incubation. This hen was found the next day incubating an unin­ cubated clutch which had been associated with hen W-3- (initial nest).

Hen Y-3 laid no additional eggs in the usurped clutch and was dis­ rupted after incubating the nest 13 days. On July 13, hen Y-3 was found on a clutch of three eggs which she deserted at this time.

Hen W-3- was not found with any other clutches.

On the basis of nesting records, at least 10 cases of clutch adoption occurred in 1950 and probably about 20 in 1951* although adoption was actually observed only twice in 1951* The two hens observed were disrupted after 13 days of incubation and adopted second clutches the following day. The higher nesting density in 1951 was probably the principal reason for the greater degree of clutch adoption that year. Instances of clutch adoption also have been reported by

Smith (1953) and Muhlbach (195U)*

U* Nest Desertion and Abandonment

The term "desertion" applies to all nests left by hens after some type of disturbance; the term "abandonment" refers only to those -63- unincubated nests that were abandoned by hens for no apparent reason.

Nest desertion was seldom observed during the course of this study, although nesting hens were molested considerably by the writer as a result of nest-searching activity and inspection. Of 66 hens assoc­ iated with nests in 1950, three deserted from initial nests and two from second nests. One hundred and fifty-eight hens were associated with nests in 1951. Six hens deserted initial nests and two deserted second nests (Tables 3 and 9).

Table 9«

Nest Desertion and Abandonment, 1950-1951

No. Nests No. Hens No. Nests No. Nests Abandoned* Associated Deserted Breeding Year Established No. " % With Nests No. % Density** 1950 108 U2 39 66 5 7.6 750

1951 229 71 31 158 8 5.0 1260

* Unincubated ** Hens per 100 acres

The activities of the observer were probably the principal stimulus for desertion. Seven of the 13 hens deserted when they were first found on nests, and the other 6 deserted within several days after having been flushed from nests. Various authors have reported that desertion is more likely to occur during egg laying or early incubation than during the later stages of incubation (Leopold, 1933}

Stokes, 195U; Muhlbach, 195U). Similar behavior was observed in this study. Five of the deserted nests had not been incubated, seven had -61*- been incubated 8 days or less, and one could not be aged.

According to Muhlbach (195U)j the propensity of hens to desert

may be influenced by the quality of the nesting cover. YiThen com­

parisons were made during the writer's study between deserted and

successful nests, no apparent differences were detected in clutch

sizes, nest construction, amount of down and feathers in nests, and

the nesting cover.

West abandonment behavior observed in this study was similar to

that reported by Buss et al. (1951) and Stokes (195U) (page Ul), and

Stokes reported that nest abandonment increases with higher breeding

density. However, when the two years of data from the writer1s

study are compared, there was less abandonment in 19?1 when the

breeding density was about twice that of 1950 (Table 9) •

Location of Nests in Territories and in Cover Strips

Randall (19U0) found a tendency for pheasant nests to be grouped

in several small areas in hayfields. He believed the groupings of

nests were correlated with the locations of crowing areas and that

the hens belonging to a harem tended to nest within the crowing area

of the cock. The findings of Randall were substantiated in this

study since most harem hens nested within the territories of the

cocks with which they were associated, and once hens joined harems

they seldom shifted to another (Table 10).

Fifty-one hens in 19$0t and 83 hens in 1951 made up the harems

of 3 and 6 territorial cocks respectively. During 1950, 96 percent

of the hens nesting initially, 9k percent a second time, and 100

percent a third, nested within the territories of cocks with which Table 10.

Nesting of Harem Hens in Relation to Territories, 1950-1951

1950 First Nests Second Nests Third Nests No. Hens No. Hens No. Hens No. Hens No* Hens No. Hens Territorial Nesting in Nesting Outside Nesting in Nesting Outside Nesting in Nesting Outside Cock Territory Territory Territory Territory Territory Territory h 20 1 8 0 0 0 7 12 0 2 0 0 0 1 13 1 5 1 2 0

Totals U5 2 15 1 2 0 Percent 96 k 9k 6 100 0

1951

k 19 1 12 1 2 0 J 20 1 10 2 0 0 E 12 5 9 h 2 1 C 9 l 7 0 1 0 U 5 1 3 1 0 0 P k 1 3 0 0 0

Totals 69 10 hk 8 5 1 Percent 87 13 85 15 83 17 - 6 6 - they were associated. In 1951, 87 percent of the hens nesting initially, 85 percent a second time, and 83 percent a third time, nested vfithin their cock's territory. All but four harem hens nested each season (Table 2). These findings are also in accord with those of Muhlbach (195U) who reported that: "...a strong attach­ ment for their own territories existed among harem hens..."

Various authors have found evidence of a tendency for pheasants to place their nests near the edges of cover (Wight, 1930; Wight, Jr.,

1950; Hamerstrom, 1936; Erickson et al., 1951), but others have found no such tendency (Leopold, 1937J Leedy, 1938). Baskett (191*7) re­ ported a general tendency away from peripheral placement of nests as nesting density increased, when narrow strips of cover such as fence rows, road ditches, and narrow extensions of fields were considered as peripheral locations. When only nests in large fields were con­ sidered, however, such a tendency away from peripheral locations was not clearly indicated.

The locations of nests in this study were plotted to determine if hens nested more in certain portions of the cover strips. During both years, more hens nested in the center portions of strips than in the edges of strips and slightly more nests were found in the southern half of the strips than in the northern half. No differences in the cover could be observed between the northern, southern, and middle portions of the strips. Since the cover strips ran east-to- west, insolation could have been a factor in the placement of more nests in the southern half of the strips. -67-

6 . Renesting

Renesting activity was observed both years of this study. As seen in table 3 , many hens established second nests, a few nested for a third time, but no fourth nests were observed. A higher percentage of hens nested for a second time in 1951 (67 percent) than in 1950

(36 percent), when all second nestings are considered. Late stocking in 1950 would no doubt be a factor in explaining these differences,

a. Nest Re-Establishment in Relation to Stage of

Incubation

One of the objectives of this study was to determine if the likelihood of nest re-establishment is affected by the stage of incubation at the time of nest disruption. The number of hens dis­ rupted from initial and renests in each category of incubation and the number of hens renesting for both years is shown in table 1 1 .

With regard to disrupted hens, renesting data has been separated in the table into two headings: "associated" renesters and "true" renesters. This was done to make a distinction between hens which adopt clutches and are considered to be "associated" renesters and hens which build nests and lay clutches and are considered "true" renesters.

Data relative to second nesting were treated statistically using Mann's Trend Test (Mann, 19U5) to determine if the likelihood of nest re-establishment is affected by the stage of incubation at the time of disruption. Although no significant downward trend in the percentage of hens renesting was revealed when data from each year were treated separately, significance was found when data for Table 11.

Hens Renesting After Disruption From Initial and Second Nests, 1950-1951

Categories No. of Hens No. of Hens Establishing No. of Hens No. of Hens Establishing of Incubation Disrupted From Second Nests Disrupted From Third Nests (Days) Initial Nests Associated True Total Second Nests Associated True Total

1950 1-3 3 0 0 0 3 0 0 0 6-8 8 0 5 5 2 0 0 0 12-11; 9 0 k k 1 0 1 1 18-20 12 0 3 3 3 0 0 0 21-23 9 0 2 2 3 0 0 0

Totals la 0 m lit 12 0 1 1

1951 1-3 16 5 8 13 8 0 1 1 6-8 15 l 13 111 10 1 2 3 12-11; 16 l 8 9 10 1 2 3 18-20 17 2 10 12 11 0 1 1 21-23 16 1 5 6 12 0 0 0

Totals 80 10 hk 5U 51 2 6 8 -69- both years were combined, and then only when all renesting data

(associated and true renests) were used (Table 12).

This downward trend indicates that hens are more likely to re­

nest the earlier in incubation their initial nests are disrupted.

It should be noted that the figures given in the column totals in

tables 11 and 12 do not represent all nesting, since some nests could

not be assigned to a category of incubation and be disrupted because

of hatching, desertion, or other causes,

b. Renesting Interval

The time elapsing between the destruction of one nest and the

laying of the first egg in a subsequent nest has been termed the re­

nesting interval (Sowls, 19U9). Although accurate renesting intervals

have not been described for the pheasant, writers have reported them

for various other species of birds. Stieve (1918a) made an anatomical

study of the jackdaw (Coloeus monedula), typically single-brooded in

Poland, regarding their capacity to re-lay after initial eggs had been taken from their nests. He reported that re-laying generally

occurred after 2 or 3 days of rest when eggs were removed from nests

on the day the last egg of the clutch was laid, but that re-laying

did not occur if eggs were removed after the onset of incubation.

He concluded that ovulation of follicles could occur when the

regression processes, set off by incubation activity, had not yet

begun.

Laven (19ii0) discussed the findings of Stieve (1918a) in terms

of their meaning to renesting as follows: Table 12.

Hens Renesting After Disruption From Initial and Second Nests, 1950-1951 Data Combined

Categories of No. of Hens No. of Hens Establishing No. of Kens No. of Hens Establishing Incubation Disrupted From Second Nests Disrupted From ' Third Nests (Days) Initial Nests Associated True Total .Second Nests Associ.ated True Total i— ?

1 19 5 8 13 11 0 1 1

6-8 23 l 18 19 12 1 2 3

12—lli 25 i 12 13 11 1 3 k

18-20 29 2 13 15 iu 0 1 1

21-23 25 1 7 8 15 0 0 0

Totals 121 10 58 68 63 2 7 9 -71- "When the first clutch is destroyed shortly after the first lay­ ing period, re-laying occurs more promptly than when the first clutch is well advanced in incubation. The remaining follicles, after cess­ ation of laying, are soon resorbed. For a time, however, the larger follicles are capable of being rebuilt. Later in incubation, they are so regressed that they can no longer be used for replacement purposes, and thereafter the smaller follicles must go through a construction process. Accordingly, re-laying takes longer."

Laven (19U0) reported on the nesting behavior of the ringed plover (Charadrius hiaticula), a two-brooded species, and found an increase in the renesting interval when nests were destroyed at certain stages of incubation, but also a shortening of the interval when nests were destroyed late in incubation. When a first clutch had been incubated 6-12 days, the renesting interval was £-6 days.

When lU-21 days of incubation had elapsed before nest destruction, the interval was 11-21 days. After 2o days of incubation, however, the renesting interval was only 6-7 days. This reduction of the renesting interval, according to Laven, indicated a renewed regular growth of the follicles toward the end of the incubation period in this species, which normally raises two broods a year.

Nice (1937) reported that the renesting interval of the song sparrow (Melospiza melodia) did not vary according to the stage of egg laying, incubation, or because of the presence of young in the nest at the time a nest was destroyed, and that invariably, the first egg in a renest was produced 5 days after the loss of the preceding nest. -72-

Stokes (1950) found that the renesting interval of the gold­ finch, (Spinus tristis tristis), subsequent to nesting failure, varied between 6 and 21 days, and that the interval depended as much on the season of the year, as upon the stage of nesting at the time of break-up.

Sowls (19U9)(1955)> working with ducks, found that the length of the renesting interval varied with the stage of incubation when the first nest was robbed and that the longer a clutch was incubated, the longer the interval before renesting. He found that this apparent correlation was statistically significant. In a preliminary report on duck renesting in 19U9, Sowls stated that at least 1+ days elapsed before renesting, and for each additional day of incubation at the time of destruction of first nests, an average of 0.57 days more elapsed before birds began to lay their second clutches (based upon

11 renestings). However, his 1955 report was based on additional data (a total of 2I4. renestings), and he reported that at least 3 days elapsed before renesting, and for each additional day of in­ cubation at the time of destruction of first nests, an average of

0.62 days more elapsed before birds began to lay their second clutches.

The present study was designed, in part, to determine if the stage of incubation at the time hens were disrupted had any effect on the length of the renesting intervals. An effort was made to assign equal numbers of incubating hens to be disrupted to each category of incubation, so that sample sizes would be as nearly equivalent as possible. As seen in table 31, this was not accomplished -73- in 1950, since only three initially nesting hens were disrupted in the first category (1-3 days of incubation). However, in 1951, nearly equal numbers of incubating hens were disrupted in each category.

The renesting behavior of 11 hens in 1950 and U5 hens in 1951 was statistically analyzed (linear regression, Snedecor, 191+6).

For the two seasons tested separately, treatment of the data reveal­ ed no correlation between the stage of incubation of disrupted hens and the length of time elapsing before hens renested. However, when the data from both years were combined, there was a significant correlation at the five-percent level. For each additional day that first nests were incubated at the time of destruction, an average of

0 .3U days elapsed before hens began to lay in second nests.

The results of the analysis are shown graphically in figure 20 which is plotted according to standard methods of linear regression

(Snedecor, 191+6). The renesting intervals varied from 2-27 days in

1950 and from 0-25 days in 1951*

As seen in figure 20, some hens disrupted after 18 days of incubation apparently had laid first eggs in subsequent clutches with­ in a relatively few days (2-5). On the basis of what little lit­ erature there is on the subject, a hen would be unlikely to begin laying within such a short period of time after being out of prod­ uction for 18 to 20 days. However, the investigator had no reason to doubt that all of the 56 second nests used in the combined analyses were not those of true-renesting hens. When hens were found on second nests, the eggs were counted, embryos were aged, nSaeo Icbto tDsrcino is et 1950-1951 Nest, of First Destruction at Incubation of Stage on

Renesting Interval in Days 0 2 10 • = . One Nest X = Two Nests + = Three Nests Three = + Nests = Two X • =. Nest One - - ersino Lnt f eetn Interval Renesting of Length of Regression T =5.6202+0.3U16X T T — 2. 6U =5.6202+0.3U16X T tg f Incubation of Stage Figure 20. 10

15

-75- and the laying dates of the first egg of the clutches were cal­ culated. If the renesting intervals were zero or more days, if the nests were obviously not dump nests, if no unusual daily increase in clutch size occurred during the laying period, and if only one age of embryos was present, the nests were considered true renestings.

That some hens could have adopted established clutches is conceiv­ able. If hens added fertile eggs before incubation, or if no eggs were added whatsoever, only one age of embryos would have been present, and adoption could not have been detected. However, if hens laid fertile eggs in adopted clutches after having begun incubation, two or more ages of embryos would probably have been present, and the adoption could have been detected.

No previous data are available for comparison on the renesting intervals of pheasants; however, the results obtained in this study are similar to those observed for other species. For avian species that are typically single-brooded, the renesting interval is corre­ lated with the stage of incubation when nests are disrupted, i.e., the longer clutches are incubated before disruption, the longer the interval.

c. Avian Ovulation

Renesting intervals could be determined more accurately if the rate of resorption of pheasant ova after the cessation of laying and the beginning of incubation were known, and if the rate of develop­ ment of ova were known for hens renesting following interruptions at various stages of incubation. Errington and Hamerstrom (1937) reported they were unable to find references in the literature -76- concerning rates of resorption of pheasant ova or the rate of devel­ opment of ova in the event of renesting following a material break in the laying period. Kabat et al. (191*8), investigating ovulated follicles, collected the ovaries of hens which had laid known numbers of eggs and had incubated nests for known lengths of time.

These authors reported on the correlation they found between the number of eggs laid by hens and the number of ovulated follicles in their ovaries, but unfortunately they did not give any infor­ mation concerning the status of the follicles which had not been ovulated, e.g., size.

Riddle (1911)(19l6), reporting on the growth rate of ova of the

chicken (Galius domesticus), found that ova smaller than 6 milli­ meters in diameter grew quite slowly, reaching this size only after

several months1 growth, whereas ova 6 millimeters or larger grew at a rate about 26 times greater. He also reported that the time

interval between the beginning of rapid growth of a 6-millimeter

egg and ovulation of that egg from the ovarian follicle was between 5 and 8 days.

Warren and Gonrad (1939) found that the growth of ova of the

domestic chicken was greatly accelerated the last 7 to 10 days before ovulation. Romanoff (191*3) compared the growth rate of ova

of the pheasant and the bobwhite quail to that of domestic ducks

and chickens and found the growth rates essentially the samej the most rapid growth for all species occurred during the 7 days before

ovulation. -77- The work of Stieve (1918b) on the domestic chicken might aid in an explanation of how an interruption of egg laying affects the re­ laying potential of a gallinaceous bird. This author isolated laying chickens individually and the birds stopped laying within one or 2 days. The amount and quality of food they received was the same before and after confinement, and after a period of several weeks the hens began to gain weight. At intervals of several days, this investigator killed chickens and examined their ovaries macro- scopically and microscopically to determine if any changes had occurred as a result of a cessation of laying. Examination of ovaries 2 and 5 days after the birds had laid their last eggs revealed that all follicles greater than 8.5 millimeters in diameter showed signs of regression, but no sign of resoiption of yolk, whereas the follicles 8.5 millimeters or less in diameter did not show regression. After lU days of confinement some of the small follicles began to regress, and an examination of an ovary at the end of 60 days revealed that regression had occurred in almost all the follicles, but no resorption of the yolk of the largest had occurred.

These birds were not reported to resume laying.

Stieve then examined the ovaries taken from hens which had been confined and fed a diet to prevent increases in weight. These birds, after a period of non-laying, resumed laying within about one month.

After re-laying had begun, hens were killed and their ovaries examined. The ovaries appeared like those of a typical laying hen, but the investigator also found evidence of what he considered to be the remains of regressed follicles (resorption of yolk had occurred) -78- which represented follicles that had been largest at the time of the cessation of laying. He concluded from these observations that, although the largest follicles were in the process of regression as was the case when birds were fed normally, the smaller follicles continued to develop. Thus, under a controlled diet, the yolks of large follicles were completely resorped, whereas under a normal diet, they were not resorped.

Another group of chickens was underfed for various periods of time subsequent to confinement and then killed and their ovaries were examined. When underfed for more than 10 days, examination revealed that the large follicles were regressing with some resorption of yolk occurring, but the smaller ones had not as yet begun to en­ large. Stieve surmised from this that the smaller follicles cannot begin to enlarge until the large follicles have regressed to a certain undetermined point.

Stieve then slightly underfed another group of chickens before they were penned and then fed them very little after penning. Under these conditions, he found that resorption of yolk and the regression of the larger follicles occurred rapidly, in one case within 5> days, and 6 to 10 days in others. The author stated that in this last case a hen could probably re-lay within 11 days, allowing 5 days for regression of the larger ova and 6 days for a small ovum to enlarge, be ovulated, and laid.

As has been related above, Stieve found that re-laying intervals were affected by diet, with underfed chickens re-laying sooner than those fed normally. This re-laying behavior might be compared, in -79- part, to that observed for the pheasant. Comparisons should not be made between the re-laying perfonnance of the underfed chickens

(with a potential re-laying interval of 11 days) and that of the pheasants observed in this study, since supplementary feeding was done and it is doubtful that the pheasant hens were underfed. The pheasants probably did not gain v/eight; they more than likely lost weight during egg-laying and incubation (Wight in McAtee et al.,

19h5; Kirkpatrick, 19I4J4), and even though conditions of confinement and bird weight were not similar, a comparison might be made between the chickens that were fed so they did not gain weight and pheasants with long renesting intervals. These chickens resumed laying within about a month, and though an interval of I4. weeks is probably longer than for most renesting pheasants, this phase of Stieve's work might aid in the explanation of long renesting intervals sometimes observed for the pheasant.

Aside from the work of Stieve, we still have no physiological basis to account for short renesting intervals following disruption when incubation is well advanced. The work of Davis (19^2), who reported on the bursting of avian follicles at the beginning of atresia

(death or abortion of an ovarian follicle), might help clarify this problem. He stated that small eggs undergo atresia in the normal, essentially mammalian manner, but that large eggs, from which vast amounts of yolk must be eliminated, undergo an unique type of atresia, consisting of the bursting of the follicle and the extrusion of the yolk into the stroma of the ovaiy. Davis stated: "Atresia of follicles, presumably occurring throughout the reproductive cycle -80- in birds, is greatly accentuated at the cessation of the laying period... The occurrence of bursting atresia seems dependent upon the history of the individual as regards egg laying and also upon certain aspects of the reproductive physiology...n On the basis of histological studies by Davis, he reported that bursting had been observed in detail in an aberrant neotropical cuckoo, (Grotophaga ani), and a cowbird, (Molothrus bonariensis). In addition, bursting was observed by Davis in the herring gull (Larus argentatus), indigo bunting (Passerina cyanea), hummingbird (Archilochus colubris), a puff-bird (Chelidoptera tenebrosa), a wood hewer (Dendrocolaptes certhia), the domestic fowl, and pigeons.

Davis described the stages of atresia but, unfortunately, did not indicate the periods of time involved for the described sequence of events. If this bursting also is typical for the pheasant, and if it occurs more rapidly than the regression described by Stieve (1918b), it might account, in part, for the shorter renesting intervals ob­ served in the pheasant.

The interval between the cessation of egg laying and commence­ ment of any re-laying is marked by ovulation. Ovulation, then, and the factors which influence it, are the crux of the problem. Romanoff

(19U9 )j in summarizing these factors, reported that hormonal control of ovulation is under the direct control of the endocrine system which in turn is regulated by internal psychological factors and external environmental ones.

Marshall (193b) reported on the re-laying behavior of species -81-

such as the wryneck, blackbirds and others, which usually lay a

definite number of eggs in a clutch, but will continue to lay if

eggs are taken shortly after laying. He also included examples of birds such as the raven, dunlin, golden plover and others, which make repeated layings when their complete clutches are removed. He

discussed this behavior as follows: "...the repetition of ovulation must be the result of exteroceptive stimuli, though whether the

stimulus is derived from perception by the eye, or through the

tactile perception by the ventral surface of the body, is uncertain.

In any case, presumably, the stimulus must pass through the inter­ mediation of the nervous system to the pituitary and so interfere with the normal course of succession in the sexual cycle, the in­

cubation phase being postponed for a long period or indefinitely.

Moreover, if the nest of the bird is removed along with the clutch, the nest building may be repeated and the succeeding egg laying and

incubation periods are deferred accordingly, ovulation being resumed

in due course.1* Marshall concluded that: **...in all the higher

animals sexual periodicity, while conditioned by the environment, is

regulated in its successive phases by the combined integrative action

of the nervous and endocrine systems.'*

A search of the literature has revealed only fragmentary data

that might be used in a physiological explanation for the laying behavior observed in this study. Studies of the reproductive physiol­

ogy of the pheasant would add considerably to an understanding of

this behavior. -32-

d. Renesting in Relation to Time of Season

Analysis of data from this study has indicated that hens will renest a second and even a third time if previous nests are un­ successful (Table 3)j that disruption early in incubation increases the likelihood of renesting (Table 12); and that the later in in­ cubation a hen is disrupted, the longer the interval before renest­ ing (Fig. 20). In addition to the above listed phenomena, analysis of data revealed a rather pronounced relationship between the time of season nest disruption or desertion occurred and the degree of renesting. A high proportion of the hens disrupted or deserting early in a season established second nests; however, the proportion decreased the later in a season disruption or desertion occurred.

Combining both years of data, 70 percent of the hens disrupted from or deserting initial nests before the last week of June established second nests, while only 13 percent of those disrupted from or deserting initial nests after this time established second nests.

Combining both years of data for hens disrupted from or deserting second nests, 53 percent of the hens disrupted from or deserting

second nests before the second week of July established third nests, while only 2 percent of those disrupted or deserting after this time

established third nests. Periods of nest disruption and degrees of renesting are presented in tables 13 and lU.

Although other authors usually have not been able to different­ iate initial nesting attempts from renesting attempts, the seasonal

span of pheasant nesting has been discussed. Stokes (195U) reported that the onset of incubation may be delayed by adverse weather Table 13.

Hens Renesting After Disruption or Desertion, 1950

No. Hens Disrupted Second Nesting No. Hens Disrupted Third Nesting From or Deserting Hens From or Deserting Hens Weekly Periods First Nests No. Percent Second Nests No. Percent

June 3-9 k k 100 0 — 10-16 8 6 75 0 — — 17-2 3 16 h 25 0 - 2U-30 6 1 17 0 - - July 1-7 8 1 12 5 2 Uo 8-lk 2 0 - 3 0 - 15-21 - _ - 3 0 - 22-28 - - - 2 0 - July 29-Aug. U - - - 2 0 - Aug. 5 - H - - - 0 - - 12-18 —— — 1 0 —

Totals 16 56 16 2 12 Table ll;.

Hens Renesting After Disruption or Desertion, 1951

No. Hens Disrupted Second Nesting No. Hens Disrupted Third Nesting From or Deserting Hens From, or Deserting Hens Weekly Periods First Nests No. Percent Second Nests No. Percent

May 27-June 2 9 8 89 0 _ June 3-9 8 5 62 0 —— 10-16 37* 33* 89 0 — - 17-23 19 11 58 3 2 67 2U-30 7 0 - 3 2 67 July 1-7 6 1 16 6 3 50 8-11+ 1 1 100 18 1 6 15-21 1 0 — 10 0 — 22-28 - -- 10 0 — July 29-Aug. 1+ -- - 5 0 Aug. 5-11 — — — —— —

Totals 88 59 67 55 8 lit

* Includes one hen which hatched four young and was found later on a second nest. -35-

conditions, but that the terminal date for nesting may be rather con­

stant. Lyon (1952) summarized much of the literature on pheasant production and reported that although hens normally renest, no

nesting attempts are made after the end of July.

Studies of pheasants in enclosures, conducted subsequent to

the writer’s study, have added other corroborative evidence of the

relationship of season and renesting. Muhlbach (195U) observed

renesting and reported that all renesting hens had been disrupted or

had deserted initial nests before June 5» Kessler (1956) reported

renesting data for 12 hens, and hens renesting had been disrupted by June 23 or before. Semones (1956) observed h$ known nest

desertions and reported that of 25 hens renesting, all but 2 had

deserted initial nests before June 25* He also observed a decrease

in renesting as the season advanced. Data from his study and the writer’s are presented in figure 21.

The relation of season and renesting of other species has been

reported by several authors. Yeatter (193U) related that few

Hungarian partridges renest if their nests are destroyed after July

15, and that many of the pairs whose nests were broken up after

incubation was well advanced would probably fail to renest even in

late June. Yeatter also refers to a reference by Sprake (1930), who was of the opinion that in England partridges would continue to

renest, if adequate food was available, up to about the end of June.

According to Edminster (19U7), ruffed grouse renest only if initial nests are disrupted before two weeks of incubation. He

reported that it was very improbable for both hens and cocks to Percent of Hens Renesting After Disruption P - H • a U0- S 50- § H <0

100 90- 80- 0 6 70- 30- 0 2 0 1 ' - - -

May 26 June 16 June 30 July 1U July 21 July 1U July 30 June 16 June 26 May 6 May o Renesting in Relation to Time of Season of Time to Relation in Renesting Periods of Nest Disruption or Desertion Disruption Nest of Periods Figure 21. Figure June 17 July 1 July 17 June l Renests 75 ^ s (l950-5l)> ^ [ )Seubert | Semones (1956), 25 Renests 25 (1956), Semones

July 15 July

86 - - -87- reach the mating stage of the sexual cycle together after about the third week of May. The "apparent need for close synchronization of the male and female mating cycle" also has been pointed out by Allen

(193U)• Bump et al. (19U7) reported that little renesting occurred when grouse lose their nests after they have been incubated for several days. However, establishment of renests as late as about

June 16 has been observed.

Stoddard (1931) reported that although the bobwhite quail is a persistent renester, some nests are broken up too late in the season for pairs to renest.

The renesting potential of the pheasant and certain other gallinaceous birds is related to the time of season. The extent of renesting seems to be dependent upon when desertion or disruption occurs during the nesting season.

The seasonal cessation of ovulation and nest establishment is but part of the over-all phenomenon of sexual cycles and seasonal reproductive rhythmicity. A voluminous literature has resulted from investigations of the physiology of species involved and of the various environmental factors which seem to influence sexual cycles and seasonal sexual rhythms. According to Baker (1938), the main causes of breeding seasons of birds in nature are temperature and

length-of-day in the boreal and temperate zones, and rain and/or

intensity of insolation near the equator. Burger (19U9)* having reviewed much of the work, stated: "There is no evidence for any

species of bird that its reproductive rhythmicity occurs independ­

ently of controls in the external environment." -88-

Most of the research on sexual cycles and rhythmicity has dealt with photoperiodism and avian physiology, with considerable emphasis being placed upon the interactions of environmental stimuli and hormonal control of breeding physiology. Partial summaries of the reviews by Burger (19U9), Marshall (1951), WoIfson (1952), and

Greeley and Meyer (1953) are presented to show the main points of view.

Burger (19U9), in his review, concluded that experimental data are yet too fragmentary to explain seasonal reproductive rhythmicity the world over. He reported further that little is actually known of the manner in which light effects pituitary stimulation. Also, that in seasonally reproducing birds, sexual activities can occur only when a refractory period has been experienced and dissipated.

He suggested that reproductive rhythmicity would be better understood when the relation of the refractory period to environmental conditions is clearer.

Marshall (1951) was of the opinion that an internal gonad rhythm is the most important single factor in the timing of breeding seasons. He concluded that: "...no single over-all factor such as day-length or light-increment is responsible for the timing of avian breeding seasons. The breeding season is kept in step with the sun essentially by the external factors that permit nidification, ovula­ tion, and the survival of young on the habitual breeding ground.

Of these, the most important may be a safe nesting site, mild weather, and an abundance of the food on which the young are traditionally fed." -89- Wolf son (19$2) discussed certain shortcomings of the length-

of-day hypothesis and suggested that day length may be looked upon as a primary regulatory factor of migration and breeding cycles at all latitudes. He stated that: “The summation of day lengths as

such, might be the critical environmental factor in determining the time of migration and breeding cycles." He reported further that

experimental results indicated that the length of day governs the time of occurrence, rate of development, amplitude, and duration of the phases of the gonadal, fat, and molt cycles. Furthermore, before the precise relation between day-length and the physiology

of the organism can be stated in terms of excitation or inhibition, or the rate and degree of response, careful studies of the pituitary, thyroid, and adrenal glands must be made in which the synthesis and the secretion of hormones are differentiated as separate responses.

Greeley and Meyer (1953) investigated the seasonal variation

in the testis stimulating activity of male pheasant pituitary glands.

They found that the testicular weights of male pheasants closely

followed the fluctuations of pituitary gonadotropic content from

late winter to midsummer. They observed that a decline in pituitary

gonadotropic content was underway by June 20, and reason that the

pituitary was refractory to day length by that time. They discussed

the cyclic nature of reproduction in the pheasant as well as in

other birds in relation to the effect of light on the production of

gonadotropins by the pituitary. They concluded that before an

adequate evaluation could be made of the role of the environment in

the control of reproduction, especially during the refractory phase -90-

of the cycle, more information was needed concerning the seasonal

fluctuations of other pituitary hormones.

Considerable work has been done and authors have expressed

various hypotheses about the effect of environmental factors upon

sexual cycles and rhythms. Although these hypotheses probably could

be used in a general explanation of the nesting behavior observed

in this study, the precise mechanism remains obscure,

e. Reproductive Success in Relation to

Renesting and Hatching Peaks

High nest losses have been reported in nesting studies of pheasants and other species (Buss et al., 1951; Kalmbach, 1939)} however, according to Errington and Hamerstrom (1937) and Errington

(19U2), these losses may not be significant in terms of total prod­ uction as renesting may compensate for initial losses. These authors found that from 70 to 80 percent of an initial breeding population of hen pheasants had produced broods despite an average nest success of

Ul percent. Other investigators who have observed low nesting success but relatively high production have also explained this productivity in terms of compensatory renesting using Errington's analysis as their model. Baskett (19U7) analyzed his data according to the method of

Errington (19U2), and found that 73 percent of the hens renested until they succeeded, although over-all nest success was low. Erickson et al. (1951) found only 29 percent of observed nests successful, but late season brood observations indicated a much higher proportion of hens finally hatching chicks. This was attributed to second and third renestings. -91-

Gompensatory reproduction does not always occur to any great

degree, and even when it does take place, has not always resulted in

high productivity. Stokes (195W attributed high over-all nesting

success on Pelee Island to excellent hatching success with little

renesting. Yeatter (19^6) reported that extensive renesting did not

compensate for nesting losses due to flooding in late May in Illinois.

Bump et_ al. (19U7) stated that total nest mortality in ruffed grouse

cannot be compensated for by renesting as has been indicated for the pheasant since most destruction of grouse nests by predation occurs

during the latter part of incubation, and hens disrupted at this time

seldom renest.

Evidence that renesting compensates for nesting losses of ducks

has been presented by Sowls (1955)* He reported on renesting that

occurred at Delta, Manitoba, as follows: H... in 19U9, it was estimated

that at least 17 percent of all mallard nests, lU percent of all pin­

tail nests, and 9 percent of all blue-winged teal nests were renests.

In 1950* at least U8 percent of the mallard nests, J4J4. percent of the

pintail nests, and 30 percent of the blue-winged teal nests were

estimated to be renests.H He stated further that in some areas dur­

ing some years, renesting may account for nearly the entire prod­

uction.

Analysis of data obtained during this study has shown that

pheasants will renest, but as has been indicated earlier in this paper,

the degree of renesting seems closely associated with the time of

season disruption occurs (Fig. 21). Although many hens disrupted

early in the season renested, some did notj and as the end of the -92- nesting season drew nearer, very few hens whose nests were disrupted renested. This is in contrast to the renesting behavior reported by

Errington and Hamerstrom (1937)* According to their analysis, hens whose first nests failed must have renested, and those hens unsuccess­ ful in their second attempt must have nested a third time. If the renesting behavior observed in the writer1s study is indicative of the behavior of wild pheasants, renesting is not so prevalent as proposed by Errington and Hamerstrom (see Tables 13 and 111).

We have seen that some investigators have attempted to explain good over-all productivity in terms of compensatory reproduction or renesting when over-all nesting success has been low. Nesting success figures are usually obtained by calculating the percent of successful nests in relation to all nests found. This method of analysis may not be a valid one. If hens typically abandon one or more clutches before finally incubating a clutch (Buss et al., 1951), reports of low nest success become less significant. For example, an observation that only

1|Q of 100 nests had hatched, would be considered poor nest success.

However, if 50 of the nests had been abandoned, nest success viould actually be 80 percent. This would be considered good productivity.

As Stokes (19Sh) has pointed out: "If abandoned nests do not represent real nesting attempts, but merely a continuous process of egg laying without resorption of follicles, it would be more accurate to exclude abandoned nests before calculating nesting success. With this cor­ rection, the hatching success of 1|7 percent in 19U9 and l|i| percent in

1950, should be 75*6 percent and 78.5 percent respectively." The potential nesting success in the writer's study was 6l percent in -93-

1950 and 69 percent in 1951* Exclusive of abandoned nests, nesting success would have been 92 percent in 1950 and 95 percent in 1951*

Much of the over-all productivity that has been attributed to compensatory reproduction or renesting probably has been a result of initial nest success. Many nests classified as unsuccessful nesting attempts actually would never have been incubated. This suggestion would seem all the more valid, since according to the writer's data, it does not seem probable that renesting alone could have accounted for the final reproductive success reported in many studies.

Analysis of data from this study indicates that renesting, as innate behavior of the pheasant, will occur in varying degrees through­ out the nesting season, depending upon when nest disruption occurs, and upon other environmental factors. A hypothetical example has been formulated to show how potential pheasant production may be affected by renesting, and to demonstrate the associated effect of hatching chronology when disruption (by catastrophe in this example) occurs at various times throughout the nesting season (Table 15)*

A catastrophic event, e.g., mowing or flooding is assumed to occur on the following dates: May 26, June 9, June 23, June 30 and July 7*

In this example, it is assumed that no mortality occurs in a population of' 100 hens and that all renests and undisrupted initial nests are successful. Nest establishment and potential hatching information have been taken from' the data acquired in the writer's study (Tables 16 and

17). Renesting potential has been estimated from data acquired in this study and that of Semones (1956) (Fig. 21, Tables 13 and lU)• Table 15.

Pheasant Productivity as Affected by Renesting, Hatching Chronology,

and Nest Disruption at Various Times During the Nesting Season

Date of Catastrophe May 26 June 9 June 23 June 30 ___ July 7 1950 1951 ..1950 1951 1950 _ 1951 1950 1951 1950 1951 No. of hens 100 100 100 100 100 100 100 100 100 100

No. of nests established and being incubated k9 62 85 91 76 5k U6 32 22 9 No* of nests hatched(l) 0 0 2 1 2k k6 5k 68 78 91

No* of nests disrupted U9 62 83 90 76 5k ko 32 22 9

% renesting expected 90 90 75 75 35 35 10 10 5 5

No. of renests kh 56 62 68 27 19 5 3 i 0 Potential hatch( 2) 0-UU-51 0-56-33 2-62-13 1-68-8 2U-27-0 1*6-19-0 5U-5-0 68-3-0 78-1-0 91-0-0 (95) (9U) (77) (77) (51) (65) (59) (71) (79) (91)

(1) Hatching peak about one week earlier in 1951• (2) The sum of the following: (a) number of nests hatching before catastrophe occurs; (b) number of renestings; (c) successful hatching of initial nests established subsequent to catastrophe. -95-

Table 16.

Dates of Initial Nest Establishment1950-1951

No. Nests Percent Cumulative Weekly Established of Total Percentage Periods 1950 1951 1950 1951 1950 1951

April 22-28 2 1 b 1 k 1

April 29-May 5 0 2 - 2 k 3

May 6-12 b 9 8 10 12 15

13-19 6 16 12 18 2U 31

20-26 12 28 25 31 b9 62

May 27-June 2 9 13 19 15 68 77

June 3-9 8 12 17 lli 85 91

10-16 7 6 15 7 100 98

17-23 0 2 - 2 - 100

Totals U8 89 100 100 - - -96-

Table 17.

Potential Hatching Distribution, 1950-1951

Weekly No. Nests Hatched Percent Hatching Cumulative Perc ent Periods 1950 1951 1950 1951 1950 1951

June 3-9 1 1 2.2 1.1 2.2 1.1

10-16 1 16 2.2 13.0 1.1 19.1

17-23 9 21 19.5 27.0 23.9 16.1

21-30 11 20 30.1 22.5 51.3 63.6

July 1-7 11 20 23.9 22.5 78.2 91.1

8-lU 8 5 17.1 5.6 95.6 96.7

15-21 1 1 2.2 1.1 97*8 97.3

22-28 1 2 2.2 2.2 100.0 100.0

Totals 89 100.0 100.0 -97- Examination of table 15 reveals that compensatory reproduction

early in the season may add considerably to total production; however, all disrupted hens do not renest even early in the season. The period when a catastrophe would be most disastrous is at a time when initial hatching alone would be inadequate to insure good over-all productivity, when all nests have been established and those not hatched are being incubated, and when it is so late in the season that the renesting potential is low. In the hypothetical example, June 23 would be the most critical period, and a catastrophe at this time would result in many nests being disrupted and little compensatory renesting occurring

(35 percent).

Aside from the compensatory aspects of renesting, productivity also may be affected by the chronology of the hatch. As seen in table

15, hatching occurred earlier in 1951 than in 1950, but it was of no significance to over-all productivity had a catastrophe occurred early

(May 26, June 9)* However, earlier hatching would have been of major importance if a catastrophe had occurred later in the season. More of the nests had hatched by the time of later dates of catastrophe

(June 23, June 30, July 7), and with the same degree of renesting expected for both years, greater over-all productivity would have resulted in 195l»

In this hypothetical example successful reproduction can be realized if disruption occurs early enough in a season for a maximum of renesting to occur, or late enough so that a major portion of initial nests has already hatched. The renesting potential appears to be rather constant for any year; hatching chronology would seem to be -98-

more of a variable.

In a wild population hen mortality occurs and all nests are not

successful. The foregoing example is for illustrative purposes and is

not intended to portray accurately nesting behavior in the wild;

however, it does give a possible theoretical explanation of nesting behavior and final productivity as has been observed by other investi­

gators.

According to most observers, adverse weather is the principal

cause of the delay in seasonal nest establishment, and the majority of

nest disruption is a result of inclement weather, the mowing of hay

crops, and predation (Lyon, 1952). The timing of these-disruptive

events is all important when the seasonal renesting potential is con­

sidered. As discussed previously, the disruptive effect of flooding

in late May was observed by leatter (19U6). He reported that much

renesting occurred, but that it did not compensate for the earlier

losses. His report is in accord with the writer's analysis that the

renesting potential should be relatively high during late May.

Stokes (195U) found that the terminal date for nesting was fairly

constant, but that adverse weather conditions might delay the onset

of nest establishment. He stated further that a delay in nesting

might not be compensated by a prolongation of nesting, and shorter

nesting seasons would allow less chance for renesting and probably

result in lower productivity. These findings are also in agreement

with the writer's analysis that the renesting potential is low late in

the nesting season and renesting does not compensate for nests lost

at this time. -99-

The disruptive effects of flooding and hay mowing were also observed by Dustman (19U9), who studied reproductive success for

different years for the same area in Ohio. He reported that after

heavy rains and flooding on June 12 and 17, in 19 U6, many hens were

observed in large groups, and this fact led him to suspect that much nest desertion had occurred. Shortly thereafter, hens were not seen

in groups, and it was surmised that renesting was underway. However,

he found that crop harvesting activities (late mowing of hay crops and the harvesting of small grains) destroyed a large portion of the re­

nesting attempts. He stated further that: "It is conceivable that

some hens never renested following the nest desertion period due to the heavy rain and flooding.” On the basis of the data acquired in the present study, not many hens in the population observed by Dustman were likely to have renested subsequent to disruption in late June.

The catastrophe observed by Dustman might be compared to the

June 23 catastrophe date of the hypothetical example presented pre­

viously in this section. The renesting potential is low at this time

of the season and over-all production is poor, even when one assumes

that all renests are successful. Furthermore, if the renesting that

did occur subsequent to the period of flooding in Dustman's study

was relatively unsuccessful, the bulk of the over-all production must

have been the result of limited initial hatching, and in part, due to

some successful renesting of birds disrupted previous to the inclement weather, which commenced on June 12.

As a result of considerable nest disruption and unsuccessful re­

nesting, the over-all production observed by Dustman was poor — only - 1 0 0 -

50 percent of the hens observed in September had broods. In years of successful production in his area, over 70 percent of the hens were observed with broods. Dustman concluded that a large majority of the total number of nests established must be successful, no matter at what time during the reproductive season they were established, if a high level of pheasant production was to be attained.

Theoretically, initial nesting losses could be compensated for by renestingj however, in reality, renesting has less chance of success than initial nesting. Baskett (19U7) listed three advantages in having a high proportion of early nests successful: (l) early clutches average larger than late ones, thus more birds are produced in successful early nests; (2) hens which successfully hatch first clutches are less sub­ ject to additional hazards such as hay mowing and predation; and

(3) early clutches produce a more desirable type of bird for the bag than late nests. Stokes (195U) presented data, as indicated previous­ ly, of the detrimental effect of delayed nest establishment by adverse weather upon over-all production. Kabat et al. (1950) have indicated that it is highly probable that the factors which cause delayed or interrupted reproduction, such as adverse weather or some other factors which result in later brood hatching dates and broodless hens, would eventually produce a much higher rate of mortality among adults and, possibly, among the progeny of these birds than would naturally be expected. They reported further that prolonged egg-laying due to nest disturbance or other factors inhibiting the development of broodiness constitutes an abnormal stress that may result in increased suscepti­ bility to mortality of all types. - 1 0 1 -

f. Renesting Activity as Indicated by

Nest Establishment and Hatching Curves

Upon occasion, pheasant nest establishment and hatching data are plotted, and when vagaries, such as secondary peaks, are observed in the curves, investigators have attributed them to renesting activity.

Baskett (191*7) presented nest establishment curves based upon three years of data. According to him, the vagaries observed in the descents of the curves were traceable to renesting following the destruction of earlier nests. He presented evidence that curves which descended rapidly and uniformly might indicate less renesting than curves that descended slowly and with less uniformity. He concluded that nest establishment apparently followed a basic rhythm which results in a direct progression of nest establishment to a peak, and that beyond the peak, the basic rhythm was obscured by renesting. Buss (191*6) discussed nest establishment curves for non-hayfield and hayfield nests, and reported that renesting of Wisconsin pheasants resulted in typically double-peaked nesting curves which showed little variation in the distance from peak to peak between various years (about 1*0 days)(Fig. 22). Dustman (191*9) compared nest establishment and nest success curves based upon data obtained in years of both high and low pheasant reproduction. In years of high reproduction, the curve of establishment of successful nests closely followed the curve which included successful and unsuccessful nests; in years of low reprod­ uction the curves were quite dissimilar. Double-peaked establishment curves were also reported, and an examination of the data reveals that the time interval between initial and secondary peaks was about Number of Nests Established 0 1 15“ 20 - - U -13 (5lHayfield and

1-18 ii -23

h- 2 Q 5-3 5*^ 5-13 5-18 5-18 5-13 5*^ 5-3 Sh NestEstablishment Data, (19U6) Buss Non-Hayfield Nests - Data Combined J.by L.Seubert) Time Periods(5-day) Figure 22. 5-23

5-26

6-2

6-7

6-12 6-17 6-17 6-22

6 ^

2

7-2 ?

102

- ■ -103-

30 days. Blouch and Eberhardt (1953) reported double-peaked hatch­ ing curves when they plotted hatching data obtained for various areas in Michigan. They postulated that the second peaks were the result of renesting, and that spring plowing was probably the disruptive factor.

The nesting data obtained in the writer's study present an excellent opportunity to investigate the character of nesting and hatching curves, since a variety of data can be plotted, i.e., initial nests or all nests (including renests). When initial nest establish­ ment data are compared for 1950 and 1951* similar trends in nest establishment are apparent (Fig. 23). Nesting began about the same time, rose rapidly to a peak and then descended more slowly. In the writer's opinion, this trend of establishment is probably typical for initial nesting, and these data correlate well with the hatching distribution presented by Stokes (195U), who found little renesting during both years of his study.

When nest establishment data from the present study are plotted using all nests (unattached, initial, and renests), vagaries due to renesting are observed in the descents of the curves (Fig. 2U). These irregularities are not as pronounced in 1950 as in 1951, since less renesting occurred in 1950j however, the shape of the 1950 curve is atypical when compared to the trend of initial nest establishment as seen in figure 23. Renesting activity was considerable in 195lj and the pronounced secondary peak in the nest establishment curve is an indication of this activity. The interval between initial and second­ ary peaks was about 25 days both years. Number of Nests Established 30- 25- 0 2 io- 15- o 5- -

■ Nest Establishment Data, Initial Nests, 1950-1951 Weekly PeriodsWeekly Figure 23* 9 0 195 5-20 (U8 initial nests) 5-27 1951 (89 initial(89 nests) 6^3 6-10 6-17 .p- k t Number of Nests Established 10 15- 30- 20 25- 35- - - I 4.-22

-9 - 5-b 5-1 b - 5 5-& U-29 Nest Establishment Data, All Nests, 1950-1951 1950 (108 nests) 20 5-527 Weekly Weekly Periods 1951 Figure Figure 6^3 (229 nests)

21*. 6 -'l 0

6-17 6-fcU 6-fcU 7-1 7-15 7-15 7-22

7 J 29 - 1 0 6 -

Errington and Hamerstrom (1937) indicated that nesting subsequent to June 1 was usually renestingj however, in the writer’s study, while renesting did begin about June 1, considerable initial nesting also occurred during the first half of June. Because of this overlapping and since nesting periods vary from season to season and from area to area, calendar dates probably should not be used to differentiate between nest types. Investigators probably have been correct, in the main, in their interpretations of vagaries, such as secondary peaks of nest establishment and hatching curves as representing renesting activity.

E. Behavior of Hens with Broods

1. Number of Clutches Hatched

During both years of this study, a few of the nests were not dis­ rupted and the hens brought off broods. Twenty-four chicks hatched from three nests in 19^0, and 70 chicks from nine nests in 195>1» Since the presence of chicks could possibly influence the renesting of dis­ rupted hens, some clutches were allowed to hatch so there would be hens with broods in the study enclosure, thus duplicating, to some degree, conditions in the wild.

2. Behavior of Hens at Hatching

All of the clutches were not observed hatching, but of those that were, the hens usually left the nests with their broods within a few hours after hatching. One hen, however, brooded young in the nest and did not leave the nest with the brood until the day after the young had hatched. -107- 3. Movements of Broods

Once a nest had been vacated, the hen usually remained for several hours within a few feet of the nest sitej however, after several days had elapsed, one could expect to see them almost anywhere in the en­ closure. Different broods were seldom seen together, although brood- less hens were frequently seen feeding in the company of hens with broods.

Brood Defense

Hens with broods were usually quite pugnacious when disturbed during the hatching period and when the chicks were very young. When chicks were disturbed, they either ran or flew to cover, and once there, apparently remained motionless. Hens defended broods less aggressively as the young became older, and would usually leave the brood when it was disturbed, returning once the disturbance had ended.

5* Adoption of Broods

One instance of a hen adopting another henTs brood was observed in 1951* Hen G-6 hatched 15 young of an initial clutch on June 2i|.

On July 13, she was observed without her chicks and in an emaciated condition. On July 18, the brood formerly in the company of the hen

G-6 was being brooded by the hen Y-0, which had been disrupted from a second nest on July 7 after 21 days of incubation. This hen was ob­ served with her adopted brood from this data on. On July 2U, G-6 hen was found dead of unknown cause.

F. Bird Losses

Losses of breeding stock for both years of this study are summarized in table 18. The greatest loss each year was through avian predation. -108-

Table 18.

Adult Bird Losses, 1950-1951

1950 1951 Cause of Loss Cocks Hens Cocks Hens

Avian Predation 0 Ik 0 20

Mammalian Predation 0 1 0 2

Disease or Paralysis 0 0 0 h Injury 0 0 0 1

Unknown 1 k 2 7

Total observed mortality 1 19 2 3k Birds unaccounted for at time of release in fall.* 3 3 0 11 *Most of these losses occurred shortly before fall release. Some probably were due to poaching. -109-

During the 1950 season, lU of the 20 birds lost were judged to be avian kills; in 1951* 20 of the 36 losses were believed due to avian predators.

There were two periods of avian predation in 1950, one preced­ ing the period of nest establishment (six kills), and the other subsequent to the incubation period (seven kills). During 1951* the majority of avian kills occurred before the peak of nest establish­ ment (19 kills), with but one kill observed subsequent to the main incubation period.

Initial periods of avian predation for both years terminated by the second week of May. By this time, the height and density of the vegetation in the area afforded excellent cover. This cover is believed to be the main reason for the cessation of avian predation, which was principally nocturnal. Of course, the feeding habits of the suspected main predator species, the great horned owl (Bubo v. virginianus) may change at a time in the spring coincident with the occurrence of good pheasant cover. During the 1950 season, no control measures were practiced against avian predators, but in 195lj pole trapping was done and five great horned owls were caught.

Since the investigator actually observed only one instance of predation, the majority of the kills were attributed to a predator type, i.e., avian or mammalian, only after careful inspection. The kills attributed to avian predators usually were found early in the morning; most of them had been fed upon in the head and neck region

(head quite often gone); the plastic identification markers had frequently been pulled intact from the bird at their point of - 1 1 0 -

attachment; and talon punctures were usually found on both the carcass

and the plastic markers (Fig. 25). One instance of probable mammalian predation occurred within the enclosure, and in another instance, dogs

killed two birds which managed to flutter over the enclosure fence. Figure 2$.

Avian Kill XV. Summary and Conclusions

A search of the literature has revealed few valid data concerning renesting by the ring-necked, pheasant even though renesting be­ havior has been accepted by investigators as a common occurrence.

A controlled study of the renesting behavior of semi-confined pheasant populations was carried out during 1950 and 1951 in central Ohio. A research area of 7*85 acres was established in a field of first-year mixed hay; the area was fenced; portions of the cover within the area were killed and alternate 16-foot strips of cover and bare ground were maintained during both years of the study; observation towers were built; predator control measures were taken; brailed, individually marked game-farm birds were released into the area each spring of the two years of the study; observations of breeding and nesting behavior were made; nests and nesting hens were located by periodic searching of the cover strips; embryos were aged and nests were randomly assigned to categories of incubation; and nesting hens were disrupted from nests at various stages of incubation.

The breeding behavior observed during the course of this study was similar to that reported for wild populations, regardless of the fact that birds were brailed and confined, and cover conditions were probably atypical.

In 19$0j 3 of the 12 cocks stocked in the enclosure established territories, and in 1951* 6 of 15 cocks stocked became terri­ torial. Once that all territories had been established during arty one year, no gross fluctuations in territorial sizes were observed.

Nine of 12 cocks in 1950* and 9 of 15 cocks in 1951 were non­ territorial. The non-territoriality observed in this study may have been due to unnatural confinement, high cock densities, or a continuation of behavioral patterns established before release.

Harems were formed at the time of territorial establishment or shortly thereafter during both years of this study. The majority of the hens became associated with harems both years, and harem sizes varied between 12 and 25 hens in 1950 and between 6 and 23 hens in 1951* When hens had definitely associated themselves with specific harems they seldom shifted to another, even after being disrupted from nests.

The largest harems and territories observed in this study were those established the earliest.

There was no indication that territorial competition among cocks or high breeding density adversely affected breeding and nesting activity during this study.

The chronology of the laying behavior of hens observed in this

study was as follows: the laying of single eggs (dropped eggs) apparently at random, the laying of eggs in dump nests, the laying in nests which were abandoned, and finally the laying in nests of

eggs which were eventually incubated.

The clutch size of initial nests was found to be significantly

greater than the clutch size of second nests; however, initial - 1 1 k -

nests could not be distinguished from renests on the basis of

clutch size.

11. Over-all egg fertility was higher in 1951 than in 1950; however,

fertility was lower for second nests both years. Fertility

percentages for first and second nests were 89 and 83 percent

in 1950, and 95 and 89 percent in 195l»

12. During both years of this study, nesting occurred from late April

to late July. Wo initial nests were established after June 21

either year, but some second nests were established relatively

early in the season. Peak of nest establishment occurred during

the same weekly period both years and median nest establishment

occurred about the same date both years.

13. Nest desertion was seldom observed during the course of this

study, although nesting hens were molested considerably as a

result of nest searching activity and nest inspection.

1U. Nest abandonment behavior is discussed and was found similar to

that reported by other authors. Nest abandonment was found to

decrease with a doubling of the breeding density in 1951*

15* During both years of this study, the majority of the hens in

harems nested within the territories of the cocks with which they

were associated. During 1950, 96 percent of the hens nesting

initially, 9k percent a second time, and 100 percent a third time,.

nested within the territories of cocks with which they were

associated. In 1951, 87 percent of the hens nesting initially,

85 percent a second time, and 83 percent a third time, nested

within their cock's territory. -115- 16. During both years, more hens nested in the center portions of the

cover strips than in the edges. Slightly more nests were found

in the southern half of the strips than in the northern half.

17 • Renesting activity was observed both years of this study.

Although many hens established second nests and a few nested for

a third time, no fourth nests were observed. Of the hens dis­

rupted from or deserting initial nests in 1950, 36 percent estab­

lished second nests, and 13 percent of the hens disrupted from or

deserting second nests established third nests. In 1951, 67

percent of the hens nested after desertion or disruption from

initial nests, and lU percent of the hens disrupted from or

deserting second nests established third nests.

18. When data from both years were combined and analyzed statistically,

more hens whose nests were disrupted early in incubation renested

than did hens whose nests were disrupted later in incubation.

No such correlation was found when the data for each year were

analyzed separately.

19* The time elapsing between the destruction of one nest and the

laying of the first egg in a subsequent nest has been termed the

renesting interval, and the present study was designed, in part,

to determine if the stage of incubation at the time hens were

disrupted had any effect on the length of the renesting interval.

The renesting data on 11 hens in 1950 and hS hens in 1951 were

analyzed statistically. For the two seasons tested individually,

no correlation was found between the stage of incubation of dis­

rupted hens and the length of time elapsing before hens renested. -116-

However, when the data for both years were combined, there was a

significant correlation at the five-percent level, i.e., the

longer clutches were incubated before disruption, the longer the

renesting intervals. For each additional day that first nests

had been incubated at the time of disruption, an average of 0.3U

days elapsed before hens began to lay in second nests.

20. A search of the literature has revealed only fragmentary data that

might be used in a physiological explanation for the laying be­

havior observed in this study. Renesting intervals could be

determined more accurately if the rate of resorption of pheasant

ova after the cessation of laying and the beginning of incubation

were known, and if the rate of development of ova were known for

hens renesting following interruption at various stages of in­

cubation.

21. Regardless of the stage of incubation when hens deserted or were

disrupted from nests, they rarely renested unless disruption or

desertion occurred early enough in a season. Although a high

percentage of the hens renested when disrupted or deserting early

in a season, the degree of renesting decreased as the season

progressed.

22. The seasonal cessation of ovulation and nest establishment is

discussed with relation to sexual cycles and seasonal reproductive

rhythmicity. Although considerable work has been done concerning

the effect of environmental factors upon sexual cycles and rhythms,

the various hypotheses presented probably could be used in but a - 1 1 7 -

general explanation of the nesting behavior observed in this study.

The precise mechanism remains obscure.

23. Renesting as compensatory reproduction is discussed in relation

to nest abandonment. Much of the over-all productivity that has

been attributed to renesting by other, authors probably has been

a result of initial nest success. On the basis of the results of

this study, it is unlikely that the final reproductive success

reported in many studies could have been the result of renesting

alone.

2I4.- A hypothetical example is presented to show how potential pheasant

production may be affected by renesting and by the chronology of

hatching when disruption (by catastrophe) occurs at various times

throughout a nesting season. The example is discussed with the

conclusion that successful reproduction can b e realized if nest

disruption occurs early enough in a season for a maximum of re-

neating to occur, or late enough so that a major portion of the

initial nests have already hatched. If the nesting behavior

observed in this study is also typical for wild populations,

cognizance of the effect of hatching chronology and of the rela­

tionship between the time of season and renesting potential

would afford a better evaluation of over-all seasonal pheasant

production.

2^. The hypothetical example is discussed in relation to studies of

wild pheasant populations, and though theoretical, does give a

plausible explanation for the nesting behavior and final prod­

uctivity observed by other investigators. - 1 1 8 -

26. Nest establishment and hatching curves are discussed. On the

basis of the data of this study, double peaked nest establish­

ment and hatching curves are an indication of renesting activity.

Other investigators probably have often been correct in their

interpretations of secondary peaks as representing renesting

activity.

27. Losses of breeding stock occurred during both years of this study,

mainly as a result of avian predation. The great horned owl

(Bubo v. virginianus) was suspected as being the principal

predator. Fourteen of the 20 birds lost in 1950, and 20 of

the 36 losses in 1951 were believed due to avian predation.

The majority of losses both years occurred either previous

or subsequent to the main nesting season. V • Literature Cited

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I, John Iyman Seubert, was born in Toledo, Ohio, July 5> 1921.

I received ray secondary education in the public schools at Fort Wayne,

Indiana, and Toledo, Ohio. Nearly all my undergraduate training was taken at the University of Toledo, Toledo, Ohio, before my entrance into the armed forces in April, 19 U3* Upon discharge from service in

September, 19U5j I attended The Ohio State University, and completed undergraduate requirements. I received the degree Bachelor of

Science from the University of Toledo in 19U6. From The Ohio State

University, I received the degree Master of Science in 19US.

Requirements for the degree Doctor of Philosophy were partially completed during the years 19U8-1952. I held an appointment as

Research Fellow of the Ohio Cooperative Wildlife Research Unit while completing work on the degrees of Master of Science and Doctor of Philosophy. I have been employed as a biologist with the South

Dakota Department of Game, Fish and Parks since 1952. Requirements for the degree Doctor of Philosophy were completed while engaged in off-campus research during the year 1956. '

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