PARENTAL BEHAVIOR 



1273 



growth rates, and the changes in growth 

 rates, are identical in a number of species. 



Riddle (1916) found that the rate of 

 growth of the ovum of the domestic hen in- 

 creased quite suddenly by a factor of about 

 25, some 5 to 8 days before ovulation (cf. 

 Stieve, 1919; ^Yarren and Conrad, 1939; 

 Marza and Marza, 1935) . In seasonal breed- 

 ing birds (including most wild birds) the 

 picture is basically the same. The ovary re- 

 mains in a regressed state during the off- 

 season; ova increase in size slowly during 

 the early part of the breeding season, then 

 very rapidly during the few days before 

 ovulation. Bissonnette and Zujko (1936) 

 found that the size of the largest ovum of 

 the female starling increases very slowly for 

 about 108 days (from December to March), 

 and then very rapidly for about 26 days. 

 During the 108-day period of slow growth, 

 the growth rate remains stable at about 0.009 

 mm. per day; it then increases quite sud- 

 denly to 0.285 mm. per day, an increase of 

 about 31.6 times. 



The 26-day period of rapid growth found 

 by Bissonnette and Zujko is based on the 

 average sizes of ova from many different 

 birds, which may have been at slightly dif- 

 ferent stages of the cycle, although collected 

 on the same days. When the sizes of the 

 various ova in individual ovaries are plotted 

 as a function of serial position, in birds that 

 are already ovulating, it becomes apparent 

 that the period of final rapid growth in any 

 one ovum is about 10 to 11 days. 



Riddle (1911) and Bartelmez (1912) re- 

 l^orted that the growth rate of ova in the 

 domestic pigeon increases sharply (by 8 to 

 20 times) starting 5 to 8 days before ovula- 

 tion {cf. Cuthbert, 1945). Stieve (19191 

 found that the volume of the largest ovum 

 of the female jackdaw, after having re- 

 mained quite constant during the months 

 before the breeding season, increases from 

 24 cu. mm. to 1600 cu. mm. during the last 

 5 days before ovulation. 



Paludan (1951) observed that the ova of 

 two species of gull, observed in the wild, 

 grew most rapidly during the last 9 to 10 

 days before ovulation. 



It is clear that the characteristic pattern 

 of growth of the avian follicle is that of a 

 long period of slow, steady growth followed 



by the sudden onset of a short period of ex- 

 tremely rapid growth which ends only when 

 the ovum is ovulated. This final period of 

 rapid growth lasts from about 4 to about 11 

 days, depending on the species. 



Relation of nest-building behavior to time 

 of egg-laying. In most species of wild birds, 

 nest-building appears to be sharply limited 

 to a few days during the cycle. Female 

 ruffed grouse begin to build about 6 days 

 before the first egg (Allen, 1934) . Tricolored 

 red-winged blackbirds (Emlen, 1941) and 

 song sparrows (Nice, 1937) start about 4 to 

 5 days before the first egg. Similar patterns 

 are found in other species of passerine birds 

 (e.g., Clark nutcracker, Mewaldt, 1956; 

 snow bunting, Tinbergen, 1939b). 



The usual description of this type of rela- 

 tionship in the literature of field ornithology 

 merely states that nest-building takes place 

 during the few days before the first egg. 

 When more exact quantitative observations 

 are made, however, the situation seems 

 somewhat more complex. Hinde (1958) 

 weighed the amount of nesting material 

 built into the nest on each day of the cycle 

 in a number of female domestic canaries. 

 He found that the intensity of nest-build- 

 ing activity reached a peak some time be- 

 fore the laying of the first egg, and then 

 waned. The timing of the peak was subject 

 to considerable variation, ranging in dif- 

 ferent individuals from 7 to days before 

 the first egg. Field observations on the cedar 

 waxwing by Putnam (1949) show a similar 

 pattern. In this species nest-building ac- 

 tivity reached a peak 2 or 3 days before the 

 laying of the first egg. 



In some species the first egg appears, not 

 immediately on the completion of the nest, 

 but after an interval of several days follow- 

 ing the last nest-building activity (purple 

 martin, Allen and Nice, 1952; white-crowned 

 sparrow, Blanchard, 1941 ; ovenbird, Hann, 

 1937; shrike, Miller, 1931). No information 

 is available concerning possible differences 

 in pre-ovulation changes in the ovary be- 

 tween species having the two different pat- 

 terns. 



Data on nest-building behavior and gon- 

 adal condition. The data so far presented 

 clearly suggest that nest-building behavior 

 is often associated with the period of maxi- 



