110 Transactions. — Zoology. 



the young birds are finally turned out the earlier-laid of the 

 next batch are within a few days of issuing from the shells. 

 Therefore the mother is confined to the nest for Httle more 

 than half the time required to hatch the first brood of the 

 season. Then, after a very few days, the process is again re- 

 peated. 



This does not occur in every nest, but it is a very impor- 

 tant item to be noted when considering the " rate of increase." 

 Moreover, in one instance at least the young birds belonging 

 to the first brood, reared in September, were themselves 

 breeding at the end of March. I can speak positively, as, hi 

 the hope of proving whether the birds of one brood mated 

 among themselves, I fastened a bit of red stuff around the leg 

 of each. The only one I saw after they were turned out by 

 their parents was a hen, which had mated with a male from 

 another brood, built a nest close to her old home, and actually 

 reared a brood of her own at the same time as her mother was 

 closing her arduous duties for the season. 



From two nests I was able to prove that seven broods 

 issued the year before last, but, for the purposes of the calcu- 

 lation I am about to make, we will take it that the average is 

 five broods of six each. This is below the mark. We then 

 allow one-third of the annual increase for deaths. Here are 

 the results : — 



First year : 1 pair : 5 broods of 6 each = 30 — ^ = 20 -f 

 original pair = 22 = 11 pairs. 



Second year : 11 pairs x 30 = 330 — i = 220 = 110 pairs 

 -f original 11 pairs =121 pairs. 



Third year: 121 pairs x 30 = 3,630 - I = 2,420 = 1,210 

 pairs + original 121 pairs = 1,331 pairs. 



Fourth year: 1,331 pairs x 30 = 39,930 - i =26,620 = 

 13,310 pairs -f original 1,331 pairs = 14,641 pairs. 



Fifth year : 14,641 pairs x 30 = 439,230 - i = 292,820 = 

 146,410 pairs -f original 14,641 pairs = 161,051 pairs; or an 

 actual increase, after allowing for deaths, of 322,100 birds. 



This does not take into account those early broods which 

 are themselves breeding, nor does it a,llow more than five 

 broods a year, while six and even seven are of common occur- 

 rence ; further, the clutches of eggs often number more than 

 six : so that we started on a low basis. And the allowance of 

 one-third is, I think, more than a,mple. 



