VOL. XIV.] OBSlillV.VnONS ON A CUCKOO. 219 



how to know when and where she would deposit her eggs and, 

 on many occasions, actually watched her do so. This fore- 

 knowledge was all the more gratifying since it enabled me 

 to invite friends to come and see the whole performance with 

 the confidence that they would not meet with disappointment. 



One result of the 1919 observations was a strengthening 

 of my previously expressed opinion that the number of eggs 

 laid by a Cuckoo in a season depended chiefly upon a regular 

 supply of suitable nests of her favourite or natural fosterers, 

 the latter being indivdduals of that species by which she 

 herself was reared ; in which circumstances she had appeared 

 willing to lay for a long period an average of an egg every 

 alternate day. It may be well to interpolate here that those 

 field-oologists who have given the most attention to the 

 Cuckoo agree that at least many females have their spheres 

 of influence, or territories, to which they return annually. 

 This can be proved beyond dispute, and this paper is addi- 

 tional evidence of the correctness of that belief. 



In anticipation of the return of the Cuckoo to this common 

 last year, I paid visits to it early in May, to study the Meadow- 

 Pipit situation. The result of close examination ultimately 

 showed that there were nine pairs in occupation of the ground, 

 six of them having eggs before the appearance of the Cuckoo. 

 Now it may not be generally reaUzed that if their eggs be 

 taken, Pipits may be relied upon to build and begin to lay 

 again usually within about eight days. This wonderful 

 provision for the maintenance of the balance of Nature is 

 practically, if not quite, universal amongst birds, for when a 

 nest of eggs from any cause whatever be destroyed, the pair 

 forthwith sets to work to rebuild and lay again. I desire 

 to lay stress upon this scientific fact, which no one can deny, 

 because there is no need for stringent legislation to protect 

 bird-life from the alleged harm done by the egg collector, 

 except in a few cases where it is most essential. 



To provide for the Cuckoo the most favourable circum- 

 stances it was obviously necessary so to order the laying of 

 these nine pairs of Meadow-Pipits that there should always 

 be a nest ready for her. At the first impression there may 

 not appear to be much difficulty about this manipulation, 

 but second thoughts will show that it needed very close and 

 thorough observation, much careful note-taking and adjust- 

 ment, in order to avoid any unfortunate lapse in the nesting 

 sequence. 



It would take up too much space here to give in detail the 

 history of each pair of Meadow-Pipits, but it may be suffi- 



