1922. BuRKiTT. — Birds' Song. 119 



Robin. — The Robins round me appear to keep each 

 to its territory all the year round, and from year to year. 

 I am famihar with over eight such permanent territories, 

 inside which each bird nests and outside which it is never 

 seen to trespass. They commonly sing against each other. 

 Each territory is about one-third of an acre, or equivalent to 

 a circle forty-five yards in diameter. We connect territory 

 with song, so would not this give one good reason why a 

 Robin sings all the year ? I think the Wrens are similar. 



Song Thrush. — From the beginning of the year 1922 

 Thrushes could be heard, especially on the less wintry days, 

 and generally before 10 a.m. Towards the end of January 

 the number increased, while judging by the sites the earlier 

 ones may have ceased. The song then ranged to perhaps 

 an hour later in the morning, with a rare one in the evening 

 (not at dusk). Throughout February the Thrushes from 

 being morning or early day singers, gradually changed 

 to being evening dusk singers, so that by the end of February 

 practically all song was at d.d.e. and lasted only for a few 

 minutes. In general there was practically no day song 

 in March. There was none in the case of known pairs. 

 Of course there were exceptions to day silence in March. 

 These seem special cases explicable as due to birds which 

 find it difficult to get a mate, such as by being in an 

 unsuitable nesting territory. I heard Thrushes on the 

 edges of streets and in railway j^ards with well marked 

 singing perches from some of which there was day song 

 from March 2nd to possibly April 30th. Also if song is 

 prolonged by the absence of a mate, the very severe weather 

 in February might have reasonably retarded mating and 

 prolonged song. But I repeat that these were quite the 

 exception. D.d.e. song went on through March and through 

 the season but always lasting for only a minute or two, 

 nothing like the d.d.m. song. 



D.d.m.. song seemed to begin with March and soon all 

 Thrushes took part in it and it increased in duration till 

 the end of March, when it lasted fifteen minutes or so. 

 I shall describe this song to the end of the season. The 

 new Thrushes (arrivals ?) which began with April seemed 

 to join in it, so that towards end of April there was a fine 



A2 



