Monogamous Instinct in Birds 



181 



That any definite evidence of "im- 

 mense antiquity" can be drawn from 

 the domesticated animals of the ancient 

 Peruvians is not of course to be ex- 

 pected. The most that may be possible 

 is to gain relative ideas of the anti- 

 quity of domes ticaition in America and 

 in the Old World. The opportunities 



of such comparisons are better with 

 plants because of the much greater 

 number of domesticated species. From 

 such considerations as seedlessness and 

 wude divergence from the nearest wild 

 relatives, the series of American crop- 

 plants appears to be older than the "Old 

 World" series. 



Do Birds Show a Monogamous Instinct? 



Recent numbers of Condor have con- 

 tained several articles on the marital tie 

 in birds, even discussing the moral issue 

 involved, constructing a sort of bird 

 morality. The contributors do not ap- 

 pear to have settled the question. L. 

 H. Miller, whose article is quoted in 

 part as follows, makes the suggestion 

 that seasonal mating may be necessary 

 to maintain the vigor of the race. 



"In the Condor for October, 1918, Mr. 

 F. C. Willard contributes a most 

 stimulating article dealing with the 

 question, 'Do birds mate for life?' In 

 support of his affirmative contention he 

 brings forward some observations re- 

 sulting from his extended field work in 

 southern Arizona. 



"His article is good and the facts 

 recorded are unimpeachable. The in- 

 terpretation of facts, however, intro- 

 duces the human element into science, 

 and hence offers a basis for divergence of 

 honest opinion. It is not my desire to 

 dispute Mr. Willard's conclusions but 

 to offer, wholly in good faith, some 

 remarks in support of the opposite side 

 of the question, so that each reader may 

 be his own judge, jury, and court of 

 appeal. 



"My first contention is that a bird's 

 activities are almost wholly the result 

 of instincts. These instincts are racial 

 characters and are transmitted from 

 generation to generation, no less truly, 

 though perhaps more variably, than is 

 color, size, or wing area. 



"My second contention is that instincts 

 are dependent for their stimulus upon 

 the physiological condition of the ani- 

 mal. Recent experiments on internal 

 secretions have been performed by the 



transplantation of reproductive glands 

 or by the infusion of tissue extracts 

 directly into the blood stream. These 

 experiments have some bearing upon our 

 problem in that they go to prove that 

 plumage differences between the sexes of 

 poultry are directly controlled by the 

 presence in the body of these germ 

 cells, and that many instinctive acts are 

 dependent, for their immediate stimu- 

 lus, upon the activity of these glands. 

 A young capon in whose body the ova- 

 ries of a hen are grafted will develop 

 the feathering characteristic of the hen. 

 The capon, without the engrafted ova- 

 ries, will develop almost as the normal 

 male. A normal female rabbit, treated 

 by hypodermic injection with the ex- 

 tract of foetus in normal salt solution, 

 will pluck the fur from her breast and 

 build a nest as though expecting a litter 

 of her own young, though none are 

 developing. 



"The theorist, however, feels it proper 

 to ask the question : Are there not bio- 

 logic reasons why a seasonal readjust- 

 ment of the marital relation would prove 

 advantageous to the race? If a pro- 

 tracted effort is required each season 

 before a mate is obtained, the less virile 

 bird will go unmated. Would not the 

 result average better for the mainten- 

 ance of tone in the race? Whatever 

 else may be claimed for the principle of 

 sexual selection, it seems to be more or 

 less vital to racial vigor. Seasonal 

 recurrence of the selective process would 

 then be classed as a sort of protective 

 adaptation in a class of animals showing 

 abundant specialization in other re- 

 spects. ^ 



' Loye Holmes Miller, The Marital Tie in Birds. The Condor, vol. 21, March-April, 1919. 



