So A Pair of Long-Eared Owls. [Sess. 



edge, then settled down on the nest and remained motionless 

 as far as we could see. For twenty minutes nothing hap- 

 pened, then the male came in from the west with loud wing- 

 claps and perched on a tree some distance from the nest. 

 Simultaneously the female uttered a new and strange note — 

 utt, utt, utt, followed by a faint ivhee. This combination was 

 repeated several times, and was answered by the male with his 

 regular oo. What this novel cry meant exactly it is hard to 

 say ; it was probably a cry of welcome to the male, but it may 

 have been a demand for food, or an expression of irritation 

 that none was brought, for, shortly after, the male flew out of 

 the wood without having gone to the nest. Whatever its 

 meaning, it was undoubtedly connected with the new phase of 

 the nesting period. 



On one or other of the two following days, March 23 or 24, 

 the first egg was laid, and the pre-nesting period, as I have 

 named it, of 1911 came to a close. 



In 1910 the first egg was laid on April 30 or May 1 — 

 some thirty-six days later than in 1911. This striking difference 

 in the laying dates of the two seasons, although not more 

 remarkable than the difference in pre-nesting behaviour, is, 

 upon one hypothesis, susceptible to explanation. We have 

 long held a theory that young birds nest later in the season 

 and lay smaller clutches than the average of their species — 

 that is to say, that birds in their first adult year reach breed- 

 ing condition more slowly than birds in their prime. At 

 present I shall not trouble you with the growing body of very 

 strong evidence in favour of this theory, but you may estimate 

 its soundness by its application to this pair of Long-eared Owls. 

 In 1910 they arrived relatively late in their nesting quarters, 

 the female took sixty-six days to reach breeding condition, and 

 laid her first egg some five weeks later than the average date 

 for the species in West Lothian ; in 1911 the birds arrived 

 twenty days earlier in their nesting quarters, and there was a 

 marked acceleration of the whole nesting business ; the female 

 took only forty-six days to reach breeding condition, and laid 

 her first egg about the average date for the species in the dis- 

 trict. There is also the additional evidence that in 1910 four 

 eggs were laid, in 1911 five, which again is probably nearer 

 the average clutch of the Long-eared Owl. The determining 



