1274 



HORMONAL REGULATION OF BEHAVIOR 



mal follicle growth. In a few cases, observa- 

 tions of follicle growth and of nest-building 

 behavior have been made on the same spe- 

 cies, and have usually led to the conclusion 

 that this association does in fact exist. Em- 

 len (1941, tricolored red-winged blackbird), 

 Paludan (1951, herring gull), Petersen 

 (1955, bank swallow), and Marshall and 

 Coombs (1957, rook) have all noted that 

 the period of nest-building coincides with 

 that of maximal follicle growth. Mr. S. 

 Glucksberg, in an unpublished study, de- 

 stroyed the nests of several pairs of ring 

 doves at the end of each day, and made 

 daily counts of the number of pieces of 

 nesting material built into the nest. He 

 found that the amount of nest-building ac- 

 tivity increased with increasing follicle size, 

 reaching a peak at the time of ovulation. 

 Similar observations have been made by 

 Clausen (1959) on the homing pigeon. 



Unfortunately, there are not yet any data 

 on nest-building and male gonadal cycles 

 to compare with those available for the re- 

 lationship of this behavior to the female 

 cycle. It is clear that the nest-building ac- 

 tivity of seasonal breeding birds in which 

 the male participates in building usually oc- 

 curs during the part of the year when tes- 

 ticular secretory activity is at its height 

 (Marshall and Coombs, 1957), but no ob- 

 servations have been made on detailed 

 changes in testicular activity, correlated 

 with detailed observations on behavior. 



4. Physiologic Induction of Nest-building 

 Behavior 



The foregoing discussion makes it plain 

 that, in the large number of species in which 

 the female does most or all of the nest- 

 building, nest-building behavior is associ- 

 ated with the final period of maximal follicle 

 activity. We may now examine evidence 

 bearing more or less directly on the prob- 

 lem of the hormonal induction of nest- 

 building behavior. This evidence may be 

 divided into two general categories: the in- 

 duction of nest-building behavior by direct 

 injection of hormones; and the elicitation of 

 nest-building behavior by external stimuli. 



Hormonal induction of nest-huilding be- 

 havior. The coincidence of nest-building be- 

 havior and the period of rapid follicle 



growth just preceding egg laying strongly 

 suggests that nest-building behavior is in- 

 duced by ovarian hormones. We have gone 

 into such detail about these and other co- 

 incidences because very little direct experi- 

 mental evidence is available, but what evi- 

 dence there is confirms the impression that 

 ovarian hormones often provide the physio- 

 logic background for nest-building behav- 

 ior. 



Lehrman ( 1958b) reported that the injec- 

 tion of 0.4 mg. diethylstilbestrol daily over 

 a 7-day period induces nest-building behav- 

 ior in ring doves. Hinde and Warren (1959) 

 indicate that the injection of estrogenic hor- 

 mone into female canaries also induces nest- 

 building behavior, but only in near-lethal 

 doses. Hinde's observations on the nest- 

 building behavior of canaries (1958) indi- 

 cate that these birds change over from the 

 use of grass to the use of feathers (which 

 is the nest lining) shortly before egg-laying 

 is due. This change-over occurs to some 

 extent even though the stimulus situation 

 in the cage remains the same (the nest is re- 

 moved daily so that the birds cannot be 

 stimulated by a completed nest) . This sug- 

 gests that the change from the use of grass 

 to the use of feathers is controlled in part 

 by a change in hormonal condition, although 

 such a change has not yet been induced by 

 means of hormone administration. The 

 suggestion is particularly interesting in view 

 of the facts that, in some species of birds, 

 the building of the main part of the nest 

 stops abruptly with the beginning of egg- 

 laying, but the addition of a lining of dif- 

 ferent material may continue thereafter, 

 and that in still other species, the male may 

 l)uild the main part of the nest, whereas the 

 female merely adds the lining (see above, 

 page 1270. 



Cole and Hutt (1953) studying a number 

 of nonlaying hens, found on autopsy that 

 some of them had ovulated, failing to lay 

 because of interrupted oviducts, impacted 

 oviducts, etc. Others had not ovulated. The 

 ovulators among the nonlayers were seen 

 to enter nests on about 47 per cent of the 

 observed days (about the same percentage 

 as in the case of normal laying hens) . Non- 

 ovulators entered the nests in only 5 per 

 cent of the cases. This indicates that the be- 



