72 THE ZOOLOGIST. 



Further Note on the Willow- Wren. — With reference to the points 

 raised by Mr. E. P. Butterfielcl in his interesting note {aiite, p. 28), it 

 is perhaps not very easy to detail closely the various grounds for 

 believing that the second broods recorded in my paper (Zool. 1910, 

 p. 401) were genuine second broods, and not merely second attempts 

 by birds whose first nests had been lost. In one case (No. 22), 

 certainly, some doubt remained, owing to the fact that no first brood 

 had been discovered, despite repeated efforts. The other nests, how- 

 ever, admitted of little doubt. Apart from their position, the fact 

 that all the pairs of birds in the immediate vicinity had successfully 

 reared their first broods settled the matter fairly satisfactorily. The 

 question of the ownership of the second nests is at times more 

 difficult to decide. To credit them merely to the builders of the 

 nearest first nest is not always safe, and the only other criteria 

 available are a comparison of dates and the rather more delicate one 

 of the identification of the parent birds. In many instances in- 

 dividuals differ in character to a degree sufficiently striking to allow 

 of distinction between neighbouring birds, apart merely from the area 

 they inhabit. At the same time, I should like to point out that my 

 estimate of the percentage of second broods is based only on two 

 years' observation in one particular wood, and may not represent the 

 actual percentage of the whole district. The same remark applies to 

 the average clutch, which for the area treated of in the above paper 

 may be stated at 6'0 in 1910. (With the inclusion of nests taken 

 elsewhere in the district in the same season, this average holds.) Eun- 

 ning through a list of Willow- Wren's nests taken within a few miles 

 of the same spot during the last five years, I find that the average 

 clutch of first broods works out at 5-9, that of the lowest year (1909) 

 being 5-6 ; but the number of nests listed is not great. This subject 

 of local averages is, I think, one of considerable interest when 

 viewed in connection with facts of latitude, climate, &c. When 

 nests found with young birds are included in the list, the average 

 arrived at may tend to be lower than the actual, since the old birds 

 sometimes eject addled eggs ; but this consideration is perhaps not 

 of great importance in the present species, owing to the small 

 number of addled eggs, and to the fact that those which occur are 

 usually allowed to remain in the nest. In this connection it may be 

 of interest to record that a nest discovered in a neighbouring wood in 

 1910, with the small clutch of four eggs, two of which were addled 

 and were later turned out by the old bird, was situated within a few 

 yards of the spot where a nest was taken in 1908, in which case 

 again the eggs were four in number, no fewer than three of which 



