PARENTAL BEHAVIOR 



1293 



ethylstilbestrol injection failed to interrupt 

 established broodiness in domestic turkeys. 

 The conditions of his experiment were some- 

 what different from those of Godfrey and 

 Jaap, since his birds were in broody coops 

 with no nests or eggs. 



Lehrman (1958b) found that untreated 

 ring doves, with previous breeding experi- 

 ence, placed in pairs in cages containing 

 nests and eggs, would begin to incubate the 

 eggs after 4 to 7 days, during which they 

 went through successive stages of courtship 

 and nest-building. If the birds were injected 

 with diethylstilbestrol (0.4 mg. per day) for 

 7 days while they were in individual isola- 

 tion cages, and then immediately placed in 

 the test cages, incubation took place in most 

 of the birds within 1 to 3 days. The estro- 

 gen-treated birds immediately engaged in 

 intensive nest-building behavior, in contrast 

 to the untreated birds. It seems probable 

 that the injected estrogen reduced the la- 

 tency of the incubation response to the 

 eggs, not by any ability to induce incuba- 

 tion behavior directly, but rather because 

 it advanced the cycle from the courtship 

 to the nest-building phase, so that events 

 could occur which lead to the onset of in- 

 cubation behavior within 2 or 3 days, and 

 which normally do not occur until after the 

 birds have been together for several days. 

 The nature of these events will be discussed 

 later. The fact that estrogen administered 

 under these conditions reduced the latency 

 of (or sped up the development of) the on- 

 set of incubation behavior does not neces- 

 sarily mean that estrogen injected during 

 incubation would not interrupt it in this 

 species. 



{3) Progesterone. Progesterone (or a ges- 

 tagen) is of particular interest in connection 

 with the onset of incubation behavior, be- 

 cause its involvement in ovulation (Roth- 

 child and Fraps, 1949; Traps, 1955) and in 

 the final stages of oviduct development 

 (Mason, 1952; Brant and Nalbandov, 

 1956; Lehrman and Brody, 1957) indicates 

 that it is present in the blood just before 

 or at about the time when incubation nor- 

 mally starts. 



Progesterone or corpus luteum prepara- 

 tions have been reported to be ineffective 

 in inducing broodiness in domestic hens 



(Riddle, 1937; Eigemann, 1937; Nalbandov, 

 1945) and canaries (Kobayashi, 1952), and 

 actually to interrupt established broodiness 

 in domestic turkeys (van Tienhoven, 1958) , 

 although in all these cases the criterion was 

 the existence of clucking and other broody 

 behavior in birds that were not given an 

 opportunity to sit on eggs. 



Riddle and Lahr (1944) implanted pellets 

 of progesterone into adult ring doves kept in 

 unisexual pairs of males or of females in 

 cages provided with a nest or eggs. All 18 

 doves tested in this way sat on the eggs, 

 most of them within 3 to 7 days after the 

 implantation of the pellets. None of the un- 

 treated control birds sat on the eggs during 

 the 3-week test period. Riddle and Lahr 

 allowed some of the progesterone-treated 

 birds to continue sitting on the eggs for the 

 normal incubation period of 14 days, and 

 then at autopsy found that the crop-sac 

 had increased in weight, as normally occurs 

 during incubation. Since it had previously 

 been demonstrated that prolactin induces 

 incubation in laying hens, and that it is the 

 hormone responsible for the growth of the 

 crop. Riddle and Lahr concluded that pro- 

 gesterone induced incubation in their ex- 

 periments because it had induced prolactin 

 secretion by the birds' pituitary glands. 

 However, Meites and Turner (1947) found 

 that progesterone (and other sex hormones) 

 when injected into pigeons, fail to increase 

 either the crop weight or the prolactin con- 

 tent of the pituitary glands. Furthermore, 

 Lehrman (1958a), who also found incuba- 

 tion behavior induced by progesterone in 

 ring doves, kept the birds in isolation during 

 a 7-day period of progesterone treatment, 

 and then placed them in pairs in test cages 

 with nests and eggs. These birds all quickly 

 sat on the eggs, most of them within 20 min- 

 utes, and were killed for autopsy immedi- 

 ately after they were found sitting. These 

 birds had crops no heavier than those of 

 untreated control birds which did not in- 

 cubate. It should be further noted that the 

 crop does not normally begin to increase in 

 weight until some days after incubation has 

 already started. Since Patel (1936) showed 

 that participation in incubation can itself 

 stimulate the secretion of prolactin by the 

 pituitary gland, it appears likely that pro- 



