Social interaction and external stimuli play a part 
in the nesting cycle, and have a direct effect on physiology 
and pertinent behavioral conditioning. Emlen and Lorenz (1942) 
implanted wild Oalfornia Quail (Lophortyx californicus) with 
sex hormone pellets and found that the untreated birds which 
ranged with the treated birds showed similar accelerated sexual 
development through social interaction. Darling (1938) and 
Paynter (1949) both suggest that the clutch size in gulls’ 
nests increased with an increase in the total number of birds 
in the colony. Lehrman et al. (1961) working with Ring Dove 
(Streptopelia resoria) introduced a mate and nests into cages 
with sexually inactive birds. He found that the addition of 
either a mate or a nest produced sexual and/or incubation be- 
havior in both sexes. Oviducts were found to have increased in 
weight and size, as compared with those of females which were 
kept alone throughout the same period. Burger (1953) showed 
testis growth in Starlings (Sturnus vulgaris) was greater in 
males caged with females than in those kept with other males. 
F.HeA. Marshall, as reported by Marshall(1954) suggested that 
these effects of social stimulation are mediated through the 
hypophysis and consequent response of the gonads. Bulough 
(1945) and Collias (1950) review the dependence of sexual be» 
haviorisms upon androgens and estrogens of the gonads. Courte 
ship singing and posturing by the male, shown by Collias (1950) 
to be caused by androgen, stimulates the receptivity of the 
female, and as Lehrman has noted, the change in vhe female's 
behavior restimulates the male to other phases of the nesting 
cycle, Males come into full sexual or breeding condition first, 
in most species, and continuance of the nesting cycle is then 
dependent upon the responsiveness of the female. Marshall (1954) 
pointed out that the female's responsiveness may be influenced 
by other external factors. Marshall and Disney (1957) showed 
that the African Red-billed Weaver (Quelec Quelea) nested only 
after rain had produced green grass, which is the traditional 
nesting material of this bird. Hinde and Warren(1959) found 
that by depriving nesting materials and space, they could re-= 
tard egg laying in canaries. Lehrman'’s (1961) inducement of 
ovulation and the appropriate incubation behavior in the Ring 
Dove simply by means of addition of eggs and nest is pertinent. 
2e Internal regulation of nesting cycle. 
One of the physological reactions which is noted early 
in the nesting cycle is the build up of calcium in the blood and 
bone which is necessary for egg shell production. Clavert and 
Benoit (1942), as reported by Simkiss (1961) showed that the 
injection of estrogens (.25 mg. per day) into 3-month-old male 
pigeons produced a 60 per: -eent increase in skeletal calcium. 
Common, Rutledge, and Hale (1948) showed that both estrogens and 
androgens were needed to cause calcium increase in females. 
Eisner (1961) indicates these two hormones are present in both 
male and female as gonadal development takes place. Simkiss 
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