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Journal of Comparative and Physiological Psychology 1975, Vol. 88, No. 1, 256-263

ESTROGEN-PROGESTERONE REGULATION OF NESTBUILDING AND INCUBATION BEHAVIOR IN OVARIECTOMIZED RING DOVES (STREPTOPELIA RISORIA)1 MEI-FANG CHENG2 AND RAE SILVER Institute oj Animal Behavior, Rutgers—-The State University The role of ovarian hormones in the induction of nest-building (tucking) and incubation behavior in female doves (Streptopelia risoria) was determined by systemic injections of estrogen, or progesterone, or estrogen combined with progesterone, or oil in reproductively experienced ovariectomized females. Combined estrogen and progesterone treatment was the most effective hormone regimen for eliciting both behavior patterns in females and also facilitated these behaviors in their untreated mates. Differences in role of the gonadal progesterone in male and female doves were discussed.

in the female dove. If intact females are treated with diethylstilbestrol, an increase in the intensity of nest building is observed when the females are introduced into the breeding cage. On the basis of this data, Lehrman (1958) suggested the possibility that courtship behavior stimulates estrogen secretion, which induces nest-building activity, and this, in turn, stimulates the release of progesterone. Progesterone was thought to (a) mediate the initiation of incubation behavior, (6) facilitate the release of an egg from the ovary, and (c) stimulate the growth of the estrogen-primed oviduct. However, Cheng (1973a) has shown that, when estradiol benzoate is administered to ovariectomized doves, the female behavior patterns described above are restored, with the exception of nest building and incubation. Also, although exogenously administered progesterone can induce incubation in the intact female (Lehrman, 1958), it is not known whether progesterone has the same effect when it is given to ovariectomized doves and whether progesterone acts alone 1 This is Contribution No. 155 from the Institute or in synergy with other ovarian horof Animal Behavior, Rutgers University. This work mone (s), such as estrogen, in producing a was supported by U.S. Public Health Service Grant behavioral effect. MH-02271 to D. S. Lehrman and M.-F. Cheng, by In the present experiment, we attempted a Rutgers Research Council Grant to R. Silver, and by a grant from the Alfred P. Sloan Founda- to define the hormonal requirements for tion. The authors are grateful to Jay S. Rosenblatt nest building and incubation behavior in the and Barry Komisaruk for their suggestions and female dove. This was done by pairing criticism of this manuscript. ovariectomized females with the intact 2 Requests for reprints should be sent to M.-F. Cheng, Psychology Department, Hunter College, males and treating the female with estrogen and/or progesterone in a temporal sequence 695 Park Avenue, New York, New York 10021. 256 From the time a pair of reproductively experienced ring doves (Streptopelia risoria) is first introduced into a breeding cage until squabs hatch some 3 wk. later, the behavior of the female changes in an elaborate and systematic way. The initial response of the female to the courting male varies among individual doves and depends upon the gonadal condition of the female at the time of introduction to the breeding situation (Cheng, 1973b). However, the order of appearance of components of female sexual behavior within a breeding cycle follows a predictable pattern as courtship proceeds. The sequence of behavior patterns has been described as a scale with 9 stages as follows: 1, nonresponsive; 2, low responsiveness; 3, approaching; 4, nest soliciting; 5, aggressive sexual crouching; 6, crouched nest soliciting; 7, nest-site defense; 8, nest-coo decline; and 9, active nest building. Experiments involving the administration of estrogens provide some understanding of the relationship between ovarian hormone secretion and reproductive behavior

OVARIAN HORMONES AND DOVE BEHAVIOR

similar to that of a normal reproductive cycle (Korenbrot, Schomberg, & Erickson, 1974; Lehrman & Brody, 1957; Silver, Reboulleau, Lehrman, & Feder, 1974). The effect of hormone treatment of the female on the nest-building and sitting behavior of her mate was also noted. Finally, it is known that the weight of the crop gland increases from resting levels of 500 mg. to over 3,000 mg. in the course of the incubation period (Hansen, 1966; Lehrman, 1964). As another indicator of the occurrence of a normal sequence of events in the breeding cycle of the hormonetreated doves, crop weights of all birds were determined at the end of the incubation period. METHOD Subjects Male and female ring doves were separated from their parents at the age of 21 days and placed in stock cages in groups of 6-10 birds. At 4 mo. of age, the sex of each bird was determined by exploratory laparotomy (Lehrman, 1955), and the birds were placed in individual isolation cages in which they were visually isolated from other birds. When the birds were sexually mature (5-6 mo. old), they were placed in pairs in breeding cages and permitted to carry out a complete reproductive cycle, which consisted of courtship, nest building, laying and incubating eggs, and rearing squabs to 21 days of age. Forty male and 40 female doves with at least one previous breeding experience were subjects in this experiment. Female doves were ovariectomized and paired with an intact, reproductively experienced male. The male of the pair was not experimentally manipulated. Each male was observed at the time of introduction to the breeding situation to ensure that he displayed bow-cooing and nest-cooing behaviors.

Cages and Rearing Conditions Housing conditions and testing cages were the same as those described in previous articles (Lehrman, 1958; Cheng, 1973b).

Procedure Table 1 indicates the temporal relationship of hormone treatment of females to events of the breeding cycle. Hormone or control injections were first administered on the fourth day (Courtship Day 4) after introduction to the breeding situation and were continued for a period of 7 days. On the eighth day (1700 hr.) and the tenth day (0900 hr.) of courtship, infertile ring dove eggs, taken from the colony, were placed in the nest of each imir of doves.

257

TABLE 1 INJECTION SCHEDULE FOR EACH EXPERIMENTAL GROUP OF OVARIECTOMIZED FEMALES Day after introduction to breeding cage

EB EB + P P Oil

4

5

6

EB EB Oil Oil

EB EB Oil Oil

EB EB Oil Oil

7

8

EB EB EB EB + P P Oil Oil Oil

9

10

EB EB EB EB + P Oil P Oil Oil

Note. Abbreviations: EB = estradiol benzoate; P = progesterone. An egg was placed in each nest on Day 8 (1700 hr.), and a second egg was placed on Day 10 (0900 hr.).

All steroids were administered in a volume of .1 cc. of sesame oil vehicle intramuscularly and alternately in the right and left pectoral muscles. The steroid doses used werefiO-Mg.EB (estradiol benzoate) and 100-/ig.P (progesterone). All doves were sacrificed on the sixteenth day of the incubation period. The body weight, crop weight, and oviduct and/or testis weights were noted. Each ovariectomized female was examined under a light microscope for ovarian fragments. Ovarian follicles were found in 6 females. The observations made on these females were excluded from the data.

Behavioral Observations Three major categories of behavior were observed: courtship, nest building, and incubation. The observation procedures differed according to the behavior patterns being analyzed. Courtship behavior. To examine courtship behavior, each pair of doves was observed at the time of introduction to the breeding cage (0900 hr.) for an initial 40-min. period and during 6-7 hourly spot checks for the remainder of the light period (lights on, 0600 hr.; lights off, 2000 hr.) throughout the experimental period (except Days 14 and 20). At these times, the sexual responsiveness of the female and the nest-oriented activity of the pair were noted. Female sexual behaviors were scored on a scale from 1 to 9, as described above. Nest-building behavior. Three categories of nest-building behavior were distinguished: (a) picking up and then dropping nest material, (b) picking up nest material and carrying it to a potential nest site, and (c) tucking nest material into the nest bowl. At the time that eggs were introduced into the breeding cage (Days 8 and 10), an experimenterbuilt nest was provided for all doves that had not built their own nests. It has been shown that the introduction of a fully constructed nest diminishes nest-building activity (White, in press). However, an incubating bird will often rearrange the nest or pull out protruding pieces of nesting material and retuck it into the nest bowl. In an attempt to stimulate nest-building activity in females that were not observed handling nest materials spon-

258

MEI-FANG CHENG AND RAE SILVER

TABLE 2 FEMALE SEXUAL RESPONSIVENESS BEFORE AND AFTEK HORMONE REPLACEMENT THERAPY OH OIL INJECTION Day8

Day 3

Day 11

Range Mdn Range Mdn Range Mdn

EB| EB + P P Oil

9 10 9 6

1-2 1-2 1-2 1-2

1 1 1 1

2-6 2-6 1-2 2

5 6 2 2

2-4 6-9 1-9 1-2

2 9 2 1

Note. Abbreviations: EB = estradiol benzoate; P = progesterone. taneously, straw was placed at an angle against the wire mesh door of the breeding cage when the female of the pair was incubating. This procedure was used no more than once daily and only during the incubation test period (Days 9-23). In addition, it was noted whether the pair of doves accepted or destroyed experimenter-built nests. Incubation. Observations of incubation behavior began the morning after the first egg was placed in the nest (Day 9). Hourly spot checks were made from 1000 hr. to 1800 hr. for the next 15 days, and it was noted whether the male, the female, or neither of the birds was sitting on the nest. A bird was scored as incubating if it was "sitting high" or "sitting well" as described by Friedman and Lehrman (1968).

Statistics Chi-square test and Tocher's modification of the Fisher one-tailed test (Siegel, 1956) were used to test the differences in proportions of birds showing nest-building behavior and incubation behavior between groups. The median test was used to test the differences in median of sexual responsiveness of female doves between treatment groups. The McNemar test was used to determine the significance of changes in nest-building behavior of individual doves before and after hormone treatment. Spearman rank-order correlation coefficient was used to compute the correlation between nesting and incubation behavior. Analysis of variance and Duncan's new multiple range test for unequal ns (Kramer, 1956) were done to determine whether there were differences in incubation behavior, crop weight, and oviduct weight among males and among females in different treatment groups. A t test for dependent samples was done to test for differences in sitting behavior in individual males from the first 4 to the last 4 days of the cycle.

RESULTS Courtship Behavior Table 2 shows the sexual responsiveness of female doves before and after EB and/or

P, or oil treatment in terms of Cheng's (1973b) scale (see above). Before hormone replacement therapy was begun (Day 3), the sexual behavior of ovariectomized females was restricted to Stage 1-2. On Day 8, after 5 days of EB (50 /u,g/day) treatment, the median stage of responsiveness was 5 and 6 for groups EB and EB + P respectively, while females that received oil or progesterone during this time remained at Stage 1-2 (Groups EB and EB + P combined vs. Groups P and Oil combined: X2 = 3.85, df = 1, p < .05). After P treatment (Day 11), EB + P females (9/10) were at Stage 9, while females (8/9) treated with only P remained at Stage 2. Interestingly, most females (8/9) treated with only EB regressed to Stage 2 (Day 11) after introduction to a nest and eggs. Nest-Building Behavior Figure 1 shows the percentage of doves in each treatment group that performed nestbuilding activities [including all components of building: picking up and dropping, carrying (performed normally by males; White, in press), and tucking] on each day of the experimental period. These activities were shown primarily by females receiving EB + P and were restricted to the time after P was administered. In Table 3, the effect of hormone treatment of the female on each component of nest-building behavior was analyzed. Although neither EB treatment alone (Group EB, Day 3-11) nor P alone (Group P, Day 11) had any effect on tucking behavior of females, all females receiving both EB + P (Day 11) showed tucking (Fisher one-tailed test; EB + P vs. EB alone, or Oil: p < .05). Also, individual females that did not show tucking behavior during the period in which they received EB alone (Group EB + P, Day 3-8) all did so after progesterone was given (Day 11: x2 = 5.14, p < .05). Only a few females in any treatment group snowed picking up and dropping of nest material (Groups EB, EB + P, P, and Oil: x2 = 7.29, p < .05). Several male doves started showing nestbuilding activities on Day 7 or 8 after introduction to the breeding cage (Figure 1), irrespective of the hormonal condition of their mates (males of Groups EB + P, EB, P,

OVARIAN HORMONES AND DOVE BEHAVIOR

259

Hormone Ireotment

So,i

?EB

!EB« p egg 2 (9AM) egg I (5PM)

Introduction to breeding edge

Introduction to breeding code Days

FIGURE 1. Percentage of doves in each treatment group that performed nest-building activities on each day of experimental period. (Abbreviations: EB = estradiol benzoate; P = progesterone.)

and Oil compared, Fisher one-tailed test, p > .05). However, a higher proportion of males paired with EB + P treated females displayed carrying and tucking of nest by Day 11 (Fisher one-tailed test, p < .05). At the time eggs were given to doves, each pair had a complete nest, constructed by either themselves or the experimenter. The last column in Table 3 shows the number of pairs of doves in each treatment group that destroyed the nest on the twelfth day after pairing. The results indicate that the tendency to destroy the nest was greatest in pairs of which the female was treated with EB or oil and least in those of which the female received EB + P (x2 = 8.85, p < .05). There is a high correlation between the occurrence of nest-building (tucking) and incubation behavior in females irrespective of hormonal treatment (r B = .84, Student's t = 2.69, p < .05). Incubation Behavior Figure 2 shows the percentage of time female and male doves in each treatment group spent incubating. The results indicate that after EB + P treatment, but not after EB alone, P alone, or oil, ovariectomized females showed incubation behavior (p
.05). Interestingly, mates of females treated with EB, P, and oil showed a significant improvement (p < .05) in duration of sitting from the first 4 to the last 4 days of incubation. Within each pair this effect on the mate appeared to be independent of the sitting behavior of the female, since there was little correlation between the duration of sitting shown by mates in any treatment group (EB + P: r - +.10; EB: r = +.36; P: r = +.51; Oil: r = +.53; p > .05). Nevertheless, there were subtle effects of hormone treatment of the female on the incubation behavior of her mate. A significantly greater percentage of males sat by the fourth day of incubation if the female received EB + P (60%) than if she received EB only (20%), P only (33.3%), or oil (33.3%; Fisher's p < .05 for EB + P vs. EB; p < .05 for EB + P vs. P; p < .025 for

EB + P vs. oil). Later in the incubation period, as a larger number of P-treated females sat, the difference between the P and EB + P males disappeared (beginning on Day 14 EB + P vs. P: Fisher's p > .05). Even though a larger number of mates of females treated with EB, P, or oil sat from the first 4 to the last 4 days of incubation, there remained a significant difference in percentage of birds sitting between EB + P and P males vs. EB only and oil males (Fisher's p < .05). There were similar increases of the proportion of females sitting from Day 10 to Day 23 (last day of incubation) for EB-, oil-, or P-treated females. On Day 10, there were significantly more EB + P treated females than EB-, oil-, or Ptreated females sitting (Fisher's p < .025). By Day 23, the difference between EB + P vs. P disappeared (Fisher's p > .05), even though the difference between EB + P vs. oil or EB was still significant (Fisher's p < .05). Crop Weight Table 5 shows crop weight of all animals at the end of the experimental period. There were no statistically significant differences TABLE 4 FREQUENCY DISTRIBUTION OF NUMBER OP DOVES INCUBATING IN EACH TREATMENT GROUP Group

EB female male EB + P female male P female male Oil female male

0-.99

i1.99

22.99

33.99

44.99

5.99

s-

66.99

7— 7.99

8 4

0

1 0

0 0









1

0

1

1

1

3 0

1 1

2 0

4 0

— 0







4

3

2

6 1

1

2 1

0

1

— 0

— 1

— 2

—.

2

5 2

1 0

0 1

0

— 0

— 1

— — 1 0

1

1

Note. Data are means of 0-.99, 1-1.99, . . . n times per day. Data were collected over a 15-day period. Males were intact and untreated. Abbreviations: EB = estradiol benzoate; P = progester-

OVARIAN HORMONES AND DOVE BEHAVIOR

in crop weight among either males or females in different treatment groups (p > .05), and there was substantial variation among individuals in crop weight. The correlation between sitting and crop weight for individuals across treatment groups is statistically significant and higher for males (r = +.74, p < .01) than for females (r = +.46, p< .01). Oviduct Weight There were no statistically significant differences in oviduct weight among females of different hormone treatments (F = .15, p > .05; Table 5, last column). This is not surprising, even though estrogen alone or the combined estrogen and progesterone treatment has been shown to augment oviduct weight (Cheng & Lehrman, 1973; Lehrman & Brody, 1957), since our measurements were taken 13 days after the last injection. Presumably, hormonal effects on the oviducts had dissipated by the time of autopsy.

261

TABLE 5 M (±.SD) CROP AND OVIDUCT WEIGHT (IN MG.) OF MALE AND FKMALE DOVES AT END OF INCUBATION PERIOD Group

«

EB EB + P P Oil

9 10 9 9

a

Male crop" 1299.2 2409.9 1562.2 1344.7

± ± ± ±

1044.7 1172.2 1080.2 1022.0

Female crop" 830.1 1220.8 1217.8 913.3

± ± ± ±

242.2 344.6 640.0 164.1

Female oviduct" 254.8 235.2 215.0 194.2

± d= ± =t

151.9 92.8 108.7 38.8

p > .05, analysis of variance.

nest-building (tucking) and incubation behaviors in females; however, progesterone injections appear to facilitate the display of sitting behavior in the P-treated female and her mate later in the incubation period. Work with other species supports the notion that the nest-oriented activities are influenced by gonadal hormones in female birds. Warren and Hinde (1959; canary), Orcutt (1965; peach-faced lovebird), and Brockway (1969; budgerigar) were able to induce nest-related behaviors with estrogen alone. Wood-Gush and Gilbert (1973) DISCUSSION showed that a synergistic action of estrogen Previous work based on estrogen treat- and progesterone stimulates nest examinament of intact female doves (Lehrman, tion and entry in hens. 1958) suggested that estrogen stimulates Both tucking nest materials and incubanest-building behavior and progesterone se- tion behavior require that the females are cretion. Progesterone, in turn, was thought physically in the nest bowl, and both behavto induce incubation behavior and to lead to ior patterns are facilitated by synergistic egg laying (Lehrman, 1965). In the present action of estrogen and progesterone. It is experiment, the role of estrogen and proges- not likely that this optimal hormonal conditerone in mediating nest building and incu- tion specifically influences only nest buildbation was examined in ovariectomized ing or only incubation, rather it probably doves. The results indicate that, although provides the optimal hormonal condition estrogen alone is sufficient to restore female under which both behavior patterns can be sexual responsiveness (Table 1; Cheng, favorably induced in response to appropri1973a), both estrogen and progesterone are ate cues (nest material for tucking and eggs necessary for the display of nest-building for incubating). Also, the mechanism of (tucking) and incubation behavior in fe- hormone action may be that estrogen and males (Figures 1 and 2). Furthermore, the progesterone facilitate the display of alprobability that an individual female dis- ready existing behavior patterns in response playing nest-building behavior (tucking) to appropriate environmental cues. This rewill also display incubation is very high sponse potential can lead to nest building (rs = +.84, p < .01). Also, pairs that incu- and incubation even under suboptimal horbate their eggs are less likely to destroy monal condition, as seen in the cases of nest their nests than are pairs that do not incu- building (Figure 1, Groups Oil, P, and EB) bate (Table 3, last column). Progesterone and incubation (Table 5, Groups Oil, EB, alone is not so effective as the combination and P; Cheng, 1973a). On the other hand, of estrogen and progesterone in eliciting behaviors may be inhibited by stimuli from

262

MEI-FANG CHENG AND RAE SILVER

the environment in the presence of the hormones, as seen in the regressed sexual responsiveness of the EB-treated females after introduction of nest and eggs. Finally, tucking and incubation behaviors continue even though hormonal effects have dissipated (as evidenced in oviduct weight), suggesting that the hormone regimen mediating the induction of tucking and incubation behaviors is probably not essential for maintaining this behavior. The present results suggest that the nestrelated activity of the male dove is dependent on the behavioral cues from the female, which, in turn, are a product of her hormonal state (Table 3). This finding is consistent with the suggestion of MartinezVargas (1971) that the female provides cues for nest-building behavior of the male in the preincubation behavior. Though the nest-related activity of the male is markedly influenced by the female, it appears that incubation behavior of some males can proceed in the virtual absence of female incubation (Figure 2, Group Oil, EB, and P). Nevertheless, there is substantial evidence to indicate that the incubation behavior of the male is influenced by the behavior of his mate. A male alone in a cage will not incubate if it is given an experimenter-built nest and eggs (Lehrman, 1958). It has also been shown that a male is more likely to incubate if it is exposed to another bird, nesting material, or a mate and that these factors act in an additive fashion to produce incubation behavior (Silver, Feder, & Lehrman, 1973). The present results suggest that in the presence of other factors even the sight of an incubating mate is not essential for the display of incubation by the male. Since females incubate from late afternoon to early morning (about 1600-1000 hr.) and males incubate during the day (Lehrman, 1965) and since observations for incubation were made from 1000 to 1800 hr., the present results probably underestimate considerably the percentage of time spent incubating by females. Nevertheless, we can assume that only those females that were seen incubating in the late afternoon incubated at night.

Our analysis also suggests that probability of incubation and duration (i.e., intensity) of incubation behavior by an individual are not always correlated. The probability of males showing incubation behavior is affected by behavioral cues and hormonal state of the female as shown above, whereas the duration of sitting is not. These differences indicate an important point: one needs to specify the kind of analysis used in discussing incubation behavior. Finally, the results indicate a difference in role of gonadal progesterone in male and female doves. When reproductively experienced male doves are castrated and given testosterone propionate replacement therapy, most show incubation behavior when they are placed in a breeding cage and permitted to proceed through a reproductive cycle with an intact female (Silver & Feder, 1973). In the present experiment, most ovariectomized females given EB replacement failed to show incubation behavior. Assay of plasma progesterone in male and female ring doves (Silver, Reboulleau, Lehrman, & Feder, 1974) indicates that there is a rise in plasma progesterone in female doves before egg laying, but no such change in progesterone levels was detected in male doves during the cycle. These results, taken together with the present experiment, indicate that although the male and female dove share in nest-building, incubation, and brooding duties, they differ in manner of sharing and in the pattern of hormonal changes underlying the behavioral changes. REFERENCES Brockway, B. F. Hormonal and experiential factors influencing the nestbox oriented behaviour of budgerigars (Melopsitiacus undulatus). Behaviour, 1969, 35, 1-26. Cheng, M.-F. Effect of estrogen on behavior of ovariectomized female ring doves (Streptopelia risoria). Journal of Comparative and Physiological Psychology, 1973, 83, 234-239. (a) Cheng, M.-F. Effect of ovariectomy on the reproductive behavior of female ring doves (Streptopelia risoria). Journal of Comparative and Physiological Psychology, 1973, 83, 221-223. (b) Cheng, M.-F. Ovarian development in the female ring dove in response to stimulation by intact versus castrated males. Journal of Endocrinology, in press.

OVARIAN HORMONES AND DOVE BEHAVIOR Cheng, M.-F., & Lehrman, D. S. Relative effectiveness of diethylstilbestrol and estradiol benzoate in inducing female behavior patterns of ovariectomized ring doves (Streptopelia risoria). Hormones and Behavior, 1973,4,123-127. Friedman, M., & Lehrman, D. S. Physiological conditions for the stimulation of prolactin secretion by external stimuli in the male ring dove. Animal Behaviour, 1968, 16, 233-237. Hansen, E. W. Squab-induced crop growth in ring dove foster parents. Journal of Comparative and Physiological Psychology, 1966, 62, 120-122. Korenbrot, C. C., Schomberg, D. W., & Erickson, C. J. Radioimmunoassay of plasma estradiol during the breeding cycle of ring doves. Endocrinology, 1974, 94, 1126-1132. Kramer, C. Y. Extension of multiple ranged tests to group means with unequal numbers of replications. Biometrius, 1956, 12, 307-310. Lehrman, D. S. The physiological basis of parental feeding behavior in the ring doves (Streptopelia risoria). Behaviour, 1955, 7, 241-286. Lehrman, D. S. Effect of female sex hormones on incubation behavior in the ring dove (Streptopelia risoria). Journal of Comparative and Physiological Psychology, 1958, 51, 142-145. Lehrman, D. S. The reproductive behavior of ring doves. Scientific American, 1964, 211, 4854. Lehrman, D. S. Interaction between internal and external environments in the regulation of the reproductive cycle of the ring dove. In Frank A. Beach (Ed.), Sex and behavior. New York: Wiley, 1965. Lehrman, D. S., & Brody, P. Oviduct response to oestrogen and progesterone in the ring dove (Streptopelia risoria). Proceedings of the Society for Experimental Biology and Medicine, 1957, 95, 373-375.

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Martinez-Vargas, C. Female control of male nest building behavior in ring doves (Streptopelia risoria). American Zoologist, 1971, 11, 4. (Abstract) Orcutt, F. S. Estrogen stimulation of nest material cutting in the immature peach-faced lovebird (Agaporis roseicollis). American Zoologist, 1965, 5,28. Siegel, S. Nonparametric statistics for the behavioral sciences. New York: McGraw-Hill, 1956. Silver, R., & Feder, H. H. Reproductive cycle of the male ring dove: II. Role of gonadal hormones in incubation behavior. Journal of Comparative and Physiological Psychology, 1973, 84, 464-471. Silver, R., Feder, H. H., & Lehrman, D. S. Situational and hormonal determinants of courtship, aggressive and incubation behavior in male ring doves (Streptopelia risoria). Hormones and Behavior, 1973, 4, 163-172. Silver, R., Reboulleau, C., Lehrman, D. S., & Feder, H. H. Radioimmunoassay of plasma progesterone during the reproductive cycle of male and female ring doves (Streptopelia risoria). Endocrinology, 1974, 94, 437-444. Warren, R. P., & Hinde, R. A. The effect of oestrogen and progesterone on the nest-building of domesticated canaries. Animal Behaviour, 1959, 7, 209-213. White, S. J. Effects of stimuli emanating from the nest on the reproductive cycle in the ring dove (Streptopelia risoria): II. Building during the pre-laying period. Animal Behaviour, in press. Wood-Gush, D. G. M., & Gilbert, A. B. Some hormones involved in the nesting behaviour of hens. Animal Behaviour, 1973, 21, 98-103. (Received November 8, 1973)