EFFECT OF EXPOSURE ON THE YOUNG 185 



A.M. only two of the young were left in the 

 nest, and though 1 searched amongst the under- 

 growth and in the gorse bush in which the nest 

 was placed, no trace of the third bird was to be 

 found. Of the two remaining young, one was 

 alive and responsive but the other was dead, 

 and though the female attended assiduously to 

 the sole surviving offspring, yet it too had 

 succumbed by the following morning. 



In a third territory, there was a nest con- 

 taining four eggs. These eggs were due to 

 hatch at much the same time as those in the 

 two nests just referred to, but they failed to do 

 so, and an examination showed that they con- 

 tained well developed but dead chicks. 



To what can the death of the young and of 

 the chicks in the eggs be attributed ? Not to 

 any failure in the instinctive response of the 

 females, for they fed their young, they brooded 

 them, they even brooded the dead as well as the 

 living, and probably did all that racial prepara- 

 tion had fitted them to do. Yet the fact that 

 the young in the second nest were lifeless and 

 exposed at 3 a.m. seems to betoken absence on 

 the part of the parents during the night, and 

 may be interpreted as a failure of the parental 

 instinctive response. Let us return for a 

 moment to the experiments. These showed, it 

 will be remembered, that a rise or fall in the 

 temperature of but a few degrees was sufficient 

 to make an astonishing difference in the length 

 of time that the young were able to survive 

 without their parents ; that when the tempera- 



