SUPPLEMENT TO BIRDS OF ESSEX COUNTY 163 



The winter of 1918-19 was unusually mild, with scarcely any snow, and 

 myrtle berries were abundant, yet these warblers were much less common than 

 in normal winters. 



These observed facts might show that the very cold weather killed off the 

 wintering birds so that there were but few of the northern-wintering clan to 

 occupy the ground in the succeeding favorable winter. Or it might show that 

 the birds were driven south the first winter and many of them preferred to go 

 south the next winter. 



It seems to me very possible that these northern-wintering birds may in time 

 develop certain characters by which they can be distinguished from those that 

 winter in the South and that a subspecies is in process of evolution. 



In the early part of the winter of 1919-20 Myrtle Warblers were especially 

 abundant. 



The feeding habits of the Myrtle Warbler in winter at Ipswich are interest- 

 ing. Besides feeding on their favorite winter food, the bay-berry or myrtle 

 berry, they are often to be seen hopping on the snow in fields eating the seeds of 

 the grasses and weeds that extend above the surface. They also visit the upper 

 edges of the marshes, hopping about over the windrows of thatch, picking up 

 seeds and perhaps insects and spiders. They also glean the small branches of 

 trees like Kinglets and hover like them on rapidly vibrating wings below a branch 

 to pick off pupas. They also cling to the bark of the trunk of a tree, resting on 

 the tail like a woodpecker, and hop up and down searching for insects. In the 

 spring they become active ily-catchers and often fly up into the air from the tops 

 of bushes or trees after insect prey. 



While still molting and very ragged in appearance, they begin to sing in a 

 feeble way. I have specimens from April 7 to 21 that show molt. 



On May 11, 1906, at Wenham, I saw a fine male give a courtship display. 

 The wings were dropped so that the yellow rump became very prominent, and the 

 yellow and black of the sides and breast became very noticeable by reason of the 

 puffing-out of the feathers. 



On October 12, 1917, at Ipswich I watched a Myrtle Warbler chasing a 

 Bluebird, flying sometimes above and sometimes below it. Another Bluebird 

 flew near and the warbler transferred its attention to him. It appeared to be an 

 instance of play. 



