30 MEMOIRS OF THE NUTTALL ORNITHOLOGICAL CLUB. 



CHAPTER IV. 

 THE SAND DUNES AND THEIR BIRDS. 



"Till the sand was blown and sifted 

 Like great snowdrifts o'er the landscape, 

 Heaping all the shore with sand dunes." 



Longfellow, "Hiawatha." 



Plum Island, Ipswich and Coffin's Beaches are backed by areas of sand 

 dunes varying from a quarter to three quarters of a mile in breadth. These 

 dunes have the same general characteristics, but the sand at Plum Island is 

 coarse and yellowish, while at Ipswich and Coffin's Beaches it is fine and white. 

 As the Ipswich dunes are historic from the discovery there of the Ipswich 

 Sparrow, a somewhat detailed description may not be out of place. The dunes 

 here as well as at Coffin's Beach have advanced within recent years, owing to 

 the cutting down of protecting tree growths, covering fertile fields and burying 

 orchards. One of these orchards at Ipswich, buried nearly to the tops of the 

 branches, still keeps alive and blossoms amid the waste of sand. A large 

 drumlin with a northwest and southeast axis, on the side of which the orchard 

 grows, is so covered with sand that it is often mistaken for a huge dune. The 

 appearance of projecting boulders, and lately, with the shifting sand, the reap- 

 pearance of an ancient fence in a gravel foundation shows its true character. 



Sand dunes are often compared to waves of the sea in their appearance and 

 motion. They do indeed resemble them with their steep and even overhanging 

 crests, as if about to break, and their long sweeping slopes behind. This 

 resemblance is made still more striking by the succession in parallel lines of 

 these waves. There is one vital difference, however, between the water and the 

 sand waves. Although they both advance, the advance of the sand waves is 

 directly opposite to that of the water waves. The sharp, steep side of the dune 

 is worn away by the wind, and streams out on the sweeping slope to leeward 

 while the wave of the sea, driven by the same wind, pushes its steep crest in 

 front. These waves of sand reach their fullest development at the southern end 

 of the Ipswich dunes. Here they form a series of parallel waves, with their 

 steep sides facing the north, that is, the direction from which come the fiercest 

 winds. These waves have advanced southward in the middle more than at 



