302 THE ZOOLOGIST. 



suitable breeding space. If that be so, one would expect that in 

 a new colony, which had unlimited room for expansion, much 

 of the sexual rivalry amongst the males would disappear. 

 Certainly Mr. Moffat's theory, if I have given it fairly, would 

 find a kind of support from the incident that I discovered. It 

 certainly seemed strange that two males of so active a species 

 as Tree- Sparrows should live so harmoniously together, unless 

 there were very exceptional circumstances, such as an extreme 

 scarcity of birds in an entirely new and isolated colony. 



Of course, the fact that the numbers in the colony have since 

 increased forms the most substantial proof that the birds only 

 began to nest here in 1907. 



I was interested to see how clearly the young Tree-Sparrows 

 showed the distinguishing marks of their species even before 

 leaving the nest. One which I examined at that stage showed 

 quite distinctly the brown head and black cheeks, and the double 

 bar on the wing. Unfortunately I have not been able to spend 

 a complete nest season in this locality, so I do not know how 

 many broods are reared by each pair, but the dates that I am 

 able to record would suggest that as many as three broods may 

 be reared in the same nesting-hole in a season. Even assuming 

 that two broods only are usual, it is strange that since the 

 colony has held its own, it has not increased at a greater rate. I 

 have worked at birds over most of this district to the south of 

 Donegal Bay, and have been on the look-out for other Tree- 

 Sparrows, but have never seen any. It is hard to believe that 

 they have not formed, or are not forming, other colonies 

 between Inishtrahull and Donegal Bay, or along the Leitrim 

 and Sligo coasts. A census of the Sparrows of both species 

 along this coast would be interesting. I have seen House- 

 Sparrows at every point between Ballyshannon and Grange, in 

 Go. Sligo, but have never seen Tree- Sparrows, except in this one 

 colony, which apparently only extends for a few hundred yards. 



