HOUSE MARTINS. 505 
MRO 
Ta 
JA pAidagyh ae 
paisa cai 
a AAU i Ne 
itu hy! | 
7h 
Fig. 220.—House Martins. 
in a sycamore tree (familiarly known there as a button-wood) near 
Louisvillein Kentucky, United States. These trees grow to an immense 
size and are generally hollow. Some of this family prefer rocks or 
caverns, and excavate in steep escarpments a gallery from two to 
