PARENTAL BEHAVIOR 



1299 



similarly carried out by both sexes. This is 

 true in birds of a number of different fami- 

 lies, such as cormorants (Mendell, 1936; 

 Kortlandt, 1940), rails (Meise, 1934), gulls 

 and terns (Tinbergen, 1953; Cuthbert, 1954; 

 Hardy, 1957), doves (Whitman, 1919), 

 swifts (Lack, 1956a j, petrels (Fisher, 1952; 

 Davis, 1957), storks (Schiiz, 1943), herons 

 (Allen and Mangels, 1940), woodpeckers 

 (Bent, 1939), and others. There are a few 

 api:)arent exceptions, such as the white- 

 tailed kite, in which it is reported that the 

 male sits on the eggs (for much less of the 

 time than does the female), but does not 

 brood the young (Hawbecker, 1942). 



In some birds, such as most of the hum- 

 mingbirds (Pitelka, 1942) and most of the 

 ducks (Delacour and Mayr, 1945), the male 

 takes no part in either incubation or any 

 aspect of the care of the young. There are 

 also a few birds, such as the phalaropes 

 (Tinbergen, 1935), in which the male does 

 all of the caring for the young. 



There are many species in which the male, 

 although he takes no part in incubation, 

 regularly feeds the young (Ryves, 1934; 

 Tinbergen, 1939b; Emlen, 1941; Skutch, 

 1953a; Armstrong, 1955; and many others). 

 It is reported for a number of species that 

 the males take no part in brooding the 

 young, although they do the major share of 

 feeding them (Nice, 1937; Rand, 1940; 

 Odum, 1941; Lea, 1942; Hinde, 1952; 

 Whitehouse and Armstrong, 1953) . 



In many species of the order Galliformes, 

 which includes the domestic chicken, the 

 male neither broods nor feeds the (pre- 

 cocial) young, but accompanies the family, 

 in effect taking part in leading them to food 

 and in guarding them, although without the 

 behavioral signs of "broodiness" {e.g., 

 clucking, characteristic body position over 

 the young, etc.) which are seen in the female 

 (Kendeigh, 1952; see Kendeigh for survey 

 of parental behavior in birds). 



In general we may say that brooding the 

 young, i.e., behavior which is associated 

 with the provision of heat by the parents to 

 young while they are still poikilothermic, 

 is done only by the sex or sexes which, in 

 that species, take part in incubation. Other 

 aspects of parental behavior, such as feeding 

 the young, leading them to food, guarding 



them, etc., may be shown (although not 

 necessarily so) by the other sex as well, even 

 though it does not particii)ate in incubation. 



2. Hormonal Induction of Parental Behav- 

 ior toward Young 



Prolactin and brooding in female birds. 

 Nalbandov and Card (1945) reported that 

 domestic hens injected with prolactin show 

 a broody response to chicks (which con- 

 sists of brooding them under body and 

 wings, leading them to feed, calling them, 

 and leading them away from danger by 

 warning signals, etc.). Similar results have 

 been obtained with pheasants (Crispens, 

 1956), and wild turkeys (Crispens, 1957). 

 Crispens treated hen pheasants witli 6 mg. 

 prolactin (presumably about 120 I.U.) per 

 day for 3 days or more, and found that 

 most of them (64 to 91 per cent in different 

 groups) accepted and brooded 2-week-old 

 Leghorn chicks. Two female wild turkeys 

 similarly treated, except that the doses were 

 larger, accepted either young turkeys or 

 young Leghorn chicks. 



None of these papers includes information 

 about the status (laying or nonlaying) of 

 the experimental birds beyond the fact that 

 they were mature females. 



Prolactin and brooding in male birds. Do- 

 mestic cocks take no part in the care of the 

 young, and sometimes even kill chicks that 

 are confined with them. We have already 

 noted that such cocks cannot be induced to 

 sit on eggs by prolactin administration. 

 However, a number of workers have re- 

 ported that prolactin induces cocks to cluck, 

 to lead, and to protect chicks under their 

 body and wings (Nalbandov, 1945; Nal- 

 bandov and Card, 1945; Yamashina, 1952). 

 According to Nalbandov and Card, prolac- 

 tin injection causes cocks to become broody 

 gradually over a 5-day period. On the 

 other hand, hens injected with prolactin be- 

 come broody quite suddenly, just as they 

 normally do at the end of their egg-laying 

 period. 



Prolactin and parental feeding in doves. 

 I have found that untreated male or female 

 ring doves, placed singly in cages with 7- 

 day-old young, would make no attempt to 

 feed them (Lehrman, 1955). When similar 

 birds were injected with 400 to 450 I.U. pro- 



