SUPPLEMENT TO BIRDS OF ESSEX COUNTY 17 



CHAPTER II 

 Birds of Limited Areas 



In the original Memoir there were chapters on the birds of the ocean, of the 

 sand beaches, sand dunes, salt-marshes, fresh-water marshes, and ponds of the 

 County, — a series of studies in ecology. In this chapter will be found several 

 bird censuses of limited areas in the County, made for the United States Biological 

 Survey, a census of warblers at Nahant and Ipswich in the height of the 

 spring migration, and a brief account of the birds frequenting Sagamore and 

 Clark's Ponds. 



The Bureau of Biological Survey of the United States Department of Agri- 

 culture, in 1914, asked ornithologists and bird observers to make censuses of the 

 birds nesting on limited areas in order to obtain some idea of the bird population 

 of the country. It was evident that in a region of forty or fifty acres very few 

 would have the time or skill to find all the nests therein made, and that some other 

 method must be employed if anything like an accurate census was to be taken. 

 It was suggested that the observer should thoroughly patrol the given area for 

 three or more early mornings at the height of the breeding season, and note the 

 species and number of singing males. It was assumed that the males sang 

 within a reasonable distance of their nests and also that it was fair to assume that 

 each singing male represented a breeding pair. The recent paper by Mr. H. 

 Mousley on the singing-tree^ confirms the fairness of this method. In a number 

 of diflferent species, mostly warblers, he found that the male almost invariably 

 sang at some special station, generally a tree, within, on the average, seventeen 

 yards of the nest. To one who has made a census and has found the same birds 

 singing morning after morning the method appeals as a fairly accurate one. 



In June, 1915, I made a study of about forty-seven acres at Ipswich, which 

 included the twelve acres where my summer house stands. My report was as fol- 

 lows : " The area studied, about a mile from the sea, comprises some forty-seven 

 acres of upland sloping to the east and south to a salt-marsh, its base washed 

 by the highest tides. The north boundary is a road running east and west; the 

 western boundary is a stone-wall grown up with bushes and rum-cherry trees. 



' Mousley, H. Auk, vol. 34, p. 339, 1919. 

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