SUPPLEMENT TO BIRDS OF ESSEX COUNTY 69 



84 [201] Butorides virescens virescens (Linn.). 

 Green Heron ; " Shite-poke." 

 Common summer resident. April 20 to October 8. 

 Eggs: May 28 to June 2. 



A common posture assumed by this heron on the sand- and mud-flats in the 

 creeks at low tide is with the back and neck horizontal and the tarsi so nearly flat 

 on the ground that the body is close to the sand and the bird resembles a log of 

 wood. In this position it waits patiently near the water ready to pounce on the 

 little fish that swim its way. 



Their common note resembles very closely the sound made by blowing a 

 blade of grass stretched tightly between the thumbs side by side, and is emitted 

 as they fly off from the intruder. When much startled I have heard them croak 

 hoarsely as they fly away. 



85 [202] Nycticorax nycticorax naevius (Bodd.). 

 Black-crowned Night Heron ; " Quawk." 



Abundant summer resident ; very rare in winter. March 27 to November 4 ; 

 December, January, February. 



Eggs: April 20 to July i. 



I have records for December 3, 1913, January i, 1914, and February 22, 

 1907, all from Ipswich. 



Although migration of this bird often takes place by day as described in the 

 original Memoir, it also takes place at night. Thus on October 6, 1918, I heard a 

 great outcry among the Night Herons in the marshes of the Castleneck River at 

 Ipswich after dark. They all seemed to be talking together. That same night 

 both Mr. R. Nichols and Mr. Ralph Lawson in Salem were surprised by the large 

 numbers of Night Herons they heard flying over toward the south. 



In the original Memoir I described a heronry of these birds at Hamilton 

 visited in 1904. In 1908, the heronry was apparently of the same size. In 191 1, 

 it was somewhat diminished as many of the white and red maples had been killed 

 by the brown-tail moth and cut out. On June 3, 1915, Dr. J. C. Phillips counted 

 150 nests there, nearly all with eggs. He found it at least twelve days behind the 

 North Beverly colony in development. 



Mr. J. F. Le Baron told me that Night Herons used to breed in large numbers 



