PARENTAL BEHAVIOR 



1275 



havior toward the nest is influenced by hor- 

 mones associated with ovidation, even in 

 those birds in which the egg could not be 

 l)roduced because of abnormalities in the 

 oviduct. 



Progesterone has not yet been shown to 

 induce nest-building behavior in birds. War- 

 ren and Hinde (1959) found that this hor- 

 mone had no effect upon nest-building in 

 the domestic canary, either alone or in com- 

 bination with estrogen. 



In view of the correlation between nest- 

 l)uilding behavior, on the one hand, and, on 

 the other hand, follicle growth, oviduct 

 growth (Petersen, 1955) , and the readiness 

 of the female to copulate, it is interesting 

 to note that estrogenic hormone induces ovi- 

 duct development in various birds (Brant 

 and Nalbandov, 1956; Lehrman and Brody, 

 1957; see chapter by van Tienhoven), and 

 female sex behavior in the domestic chicken 

 (Adams and Herrick, 1955). 



Although it is reasonably certain that 

 estrogenic hormone is the principle physio- 

 logic initiator of nest-building in those typi- 

 cal species in which the female does most or 

 all of the nest-building, the situation is 

 most unclear in those cases in which the 

 male participates. Although we have noted 

 in our laboratory that nest-building can be 

 induced in ring doves by estrogen injection, 

 and not by testosterone (see above), we do 

 not yet have adequate observational evi- 

 dence concerning the specific effects of es- 

 trogen injections on the male and on the 

 female. This evidence, when it is available, 

 will be important and interesting, because in 

 these birds the male typically brings the 

 nesting material to the nest, and the fe- 

 male builds it into the nest (Goodwin, 

 1955). In the brush turkey, the male builds 

 a large mound by scraping leaves, mold, 

 soil, etc., backwards wdth his feet. The fe- 

 male later lays the eggs in holes burrowed 

 into this mound, and they are incubated by 

 heat generated by decaying leaves and 

 mold. The male's head and neck are almost 

 featherless, and covered with a red skin. 

 This skin becomes brilliant red in each 

 breeding season, a few days before the be- 

 ginning of mound-building. This suggests, 

 of course, that in this case male sex hormone 

 is involved in nest-building activity. How- 



ever, during the period of most intense 

 mound-building activity, the male does 

 not allow the female near the area, which 

 suggests further problems about the rela- 

 tionship between male sex behavior, mound- 

 building, and the hormonal bases thereof 

 (Fleay, 1937). In the black-crowned night 

 heron both the male and the female nor- 

 mally participate in nest-building, incuba- 

 tion, and the rearing of the young. Noble 

 and Wurm (1940) found that testosterone 

 propionate would induce nest-building be- 

 havior in both males and females, whereas 

 estrogenic hormones had no effect on the 

 nest-building behavior of either sex. Fur- 

 ther, they found that the change in color of 

 the bills (yellowish to black) and legs (yel- 

 lowish to rich pink), which normally oc- 

 curs in both sexes at the beginning of the 

 breeding season in the spring, can be in- 

 duced in the off-season by injection of tes- 

 tosterone propionate, but not by estrogenic 

 hormones. The hormonal background of 

 nest-building behavior in this case is differ- 

 ent from that of the species in which the fe- 

 male alone builds the nest, but it is also dif- 

 ferent from the situation in the ring dove, 

 in which both sexes take part in building. 



These cases indicate the complexity of 

 patterns and mechanisms involved, and are 

 only a sample of the considerable variety of 

 unsolved problems posed by the nest-build- 

 ing behavior of many species of wild birds, 

 problems which are only hinted at in the 

 work so far done on domesticated birds. 



Induction of nest-building by external 

 stimnli. In species in which the female 

 builds the nest unassisted (and this includes 

 most of the species for which useful infor- 

 mation is available), it seems that stimuli 

 provided from the environment, including 

 stimuli coming from the behavior of the 

 male, may induce the hormonal changes 

 which lead to the onset of nest-building. 

 Howard (1920) described the typical breed- 

 ing pattern of many species of songbirds, 

 in which the male arrives first on the spring 

 migration, and has his territory established 

 by the time the female arrives some time 

 later. The male appears to be ready to court 

 and eager to copulate as soon as the female 

 arrives, but the female at first does not per- 

 mit copulation. There is a period of some 



