• 1
     Collections of the gonads of desert birds which were made in localities during, and soon after, severe drought revealed striking differences in reproductive development.
  • 2
     Comparatively meagre rainfall and the resultant creation of relatively beneficial conditions has a more stimulating effect on the male than on the female cycle.
  • 3
     The failure of the females to respond leads to a disturbance of the normal sequence of events in the male gonad and abnormal conditions, similar to those found in Arctic and other non-breeders, were observed in the undischarged testis. These are not readily explained by the known facts concerning the hypophysial/gonad relationship in vertebrates.
  • 4
     Desert birds have evolved an unusually high degree of nomadic mobility to defeat droughts. They exhibit a further vital physiological aspect of drought adaptation in that their sexual cycles can respond quickly to rainfall, or its effects, so that nidification may begin within a few days of heavy precipitation, irrespective of daylength and light increment. On the other hand, the gonads may remain inactive, in the true sense of the word, and reproduction can be inhibited for a succession of seasons during a prolonged drought.