201 BRITISH BIRDS. [vol. xv. 



clutch is com])Iete. If an egg be taken before the ckitch is 

 completed, the bird does not lay an additional egg. Incuba- 

 tion commences as soon as the first egg is laid and takes trom 

 thirteen to fourteen days. The young are from ten to eleven 

 days in the nest before they are full\-fledged. If a branch be 

 shaken, or a movement made near the nest, the young birds 

 open their mouths, thereby rendering themselves rather 

 cons]»icuous. as the inside of the mouth is of a bright yellow 

 colour with two black tongue-s}>ots. 



When an almost fuUy-tledged young bird was removed 

 from the nest the parent birds became very agitated and 

 often approached (|uite near. 



In e\'erv case the nest was composed of blades and stalks 

 of dried grass and contained a ^•ariable cpiantity of moss. In 

 one case a little fluff was woven into the bottom of the nest. 

 All the nests were placed within a foot or so of tracks which 

 had been made through the herbage. 



The normal clutch api^ears io be four, although one nest 

 contained ftve eggs. Tlie jxncentage of addled eggs was 

 very <mall. 



In early October I \-isited the island and lound two nests 

 which had escaped observation in June. Each contained a 

 badly discoloured addled egg. 



As a tj'pical example, the following dates may be of interest. 

 2nd June one egg ibth June two j'oung, two eggs 

 3rd June two eggs 24th June three fully fledged 

 7th June four eggs young 



qth June lour eggs 26th June young still in nest 



14th June four eggs 2nd July nest empty 



In 192 1 I was disappointed to find that the herbage on the 

 island was being cut down. However, I thought I recognised 

 the song of a IMarsh-W'arbler, and e\-entually on May 25th a 

 nest was found containing four eggs and a Cuckoo's egg. 



In June an empty nest was discovered on the banks of the 

 Thames but, on visiting it a few days later, I found that the 

 entire nest had been cut out. 



From the reports of others and my own observations in 

 1920. it appears reasonable to hope that, if unmolested for a 

 season or two, the Marsh-Warbler ma}' establish itself in the 

 county. 



