9 o IN BERKSHIRE FIELDS 



courtyard. (They often nest in hollow trees.) This 

 would seem to suggest possibilities to those com- 

 munities which are infested with sparrows. A few 

 pairs of sparrow-hawks on every block would soon 

 clean things up! 



The marsh-hawk (which is a medium-sized bird, 

 about seventeen inches long) has apparently the 

 habit of hunting over a regular beat. I have records 

 of this from points as distant as New England and 

 Mexico (the latter recorded by Charles Livingston 

 Bull). In each case the bird always appeared from 

 a certain quarter, followed a definite line of flight 

 while under observation, and disappeared at the 

 same place. When the marsh-hawk notes some dis- 

 turbance in the grass or gets sight of a mouse or 

 young woodchuck or desirable insect, he suddenly 

 stops, mounts a little, hovers watching, and then 

 strikes with great speed. It is estimated that a 

 pair will account for eleven hundred mice, small 

 birds, and other prey in the ten weeks of incuba- 

 tion and rearing of a family. Were it not for the 

 fact that something over 25 per cent, of this total 

 is sure to be birds, the marsh-hawk would not be a 

 bad fellow to have around. At the worst, he is 

 listed only as " doubtful" by most ornithologists. 

 To-day I stopped my motor beside a wide field and 

 watched one hunting. He flew low not over 

 twenty feet up and paid no attention whatever to 

 the other birds, which were numerous. He was in- 

 tently watching the ground as he flew, and when 

 he finally struck too far away for me to see clearly 

 it was at something on the ground, probably a 

 field-mouse. On the other hand, in March, when 



