TREE SPARROW 



1141 



such uniformity that I was satisfied they were both normal and 

 typical for the species. 



In 1946 Walkinshaw (1948) gathered nesting data on the western 

 tree sparrow in western Alaska. His observations and data are 

 remarkabl}'' consistent with my Churchill records and corroborate the 

 close relationsliip of the two forms. 



According to Taverner and Sutton (1934) the tree sparrow spends 

 about four months at Chiu-chill, arriving about May 25, and is seen 

 last on September 29. The occasional few of the first two days 

 (Sutton's field notes) were followed almost immediately by enormous 

 numbers of both sexes, scattered (none in flocks) through the stunted 

 willows of the river flats. In Alaska, Nelson (1887) Likewise noted 

 that flocks were broken up when they reached the breeding grounds 

 and that the birds were mated soon after. 



When I arrived at Churchill in early June, the tree sparrows were 



already established on their territories and had begun nest building. 



The successive stages of the reproductive cycle and their inclusive 



dates at three typical nests were: 



Dates of Period 



Average Length 

 Activity * Nesl I Nest III Nest IX of Period 



In the short northern summer it is highly unlikely that more than 

 one brood is reared each year. As the earliest young at Churchill 

 left the nest on July 8 and both parents continued to feed them for 

 another two weeks or more, a second brood could not have been 



