CHAPTER IX 



COURTSHIP AND SEX 



1. Physiological and Psychological. § 2. Modes of Courtship sum- 

 marised. § 3. The Mating Behaviour of Pigeons. § 4. The 

 Courtship of the Great Crested Grebe. § 5. I'he Observations 

 of Selous. § 6. The Evolution of the Voice. § 7. The Variety 

 of Bird Song. § 8. The Vocal Organs. § 9. The Interpretation 

 of Song. § 10. Reconsideration of Darwin's Theory of Sexual 

 Selection. § 11. Sex-Characters. § 12. Hormones and Sex-Cha- 

 racters. § 13. What determines Sex ? 



§ I. Physiological and Psychological 



The first chapter in the Reproductive Cycle is courtship. 

 This impHes biologically a heightening of the sex-impulses 

 which makes the consummation more certain and more 

 successful ; but it may also have a psychological significance 

 in binding the mates together, in establishing psychical 

 links, as may be illustrated by the case of the Great Crested 

 Grebe. It is difficult to steer a middle course between 

 crediting the pairing birds with too much associated feeling 

 and allowing them too little, especially difficult because the 

 courtship behaviour of birds has been carefully studied only 

 in a few cases. It should be noted that the courting does 

 not always lead up to sexual union as its immediate climax, 

 and that there is sometimes a sort of " engagement " period. 

 It should also be noted that a snatch sexual union may occur 

 apart from any courtship ceremonial and apart from subse- 

 quent co-operation of the parties. To get a fair estimate for 

 the present time it may be useful to discuss two cases that 

 have been very carefully studied, the case of pigeons, studied 

 by Whitman (19 19), where the physiological aspect is the 

 more dominant, and the case of the Great Crested Grebe, 

 studied by JuHan Huxley (19 14), where the psychological 

 aspect is more definitely expressed. 



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