96 



account of the presence of other nests in the vicinity, however, 

 it was not identified with certainty. A comparison of the 

 three completed nests shows them quite similar in construc- 

 tion and in materials used. The first two are more regular in 

 shape, however, since the third was built entirely in the growing 

 vegetation and had to be adapted to it. 



A comparison of the eggs shows a relatively normal amount 

 of variation as to color and markings, the last set having a 

 slightly darker ground color and heavier spots. The size 

 shows a gradual increase from the first to the last eggs laid, 

 as the following table of measurements shows : 



Date taken. Length. Width. 



Apr. 26, 1911 23.0 mm. 17.0 mm. 



Apr. 26, 1911 23.2 17.0 



Apr. 26, 1911 24.2 18.0 



May 6, 1911 24.2 18.0 



May 6, 1911 25.4 18.0 



May 6, 1911 27.0 19.0 



May 18, 1911 27.2 18.2 



May 18, 1911 27.2 18.4 



May 18, 1911 28.0 19.0 



The first nests built are located in the dead stubs of the cat- 

 tails that have been burned over during the previous fall. At 

 first they are not sheltered by vegetation of any kind, for the 

 new growth is barely above the water (Plate IX, fig. 1). 

 Occasionally nests are located in the tangles where the flags 

 have not been burned. As the season advances and the 

 vegetation grows, green stalks are included in the support. 

 At first these are not sufficiently strong to serve alone as a 

 support, and consequently the nests are always attached on one 

 side to a dead stub (Plate IX, fig. 2) . This is true of most of 

 the nests constructed in early May, and it generally results in 

 disaster. So firmly are the nests fastened by the strands of 

 milkweed fiber, that the side attached to the green blades is 

 carried upward by their growth, while the other, attached to 

 the dead stubs, remains fixed. As a result, the one side is 

 lifted at the rate of almost an inch a day until the nest is 

 inverted (Plate XVII, fig. 1). The birds continue to incubate 

 until the last egg is rolled out. Later, as the growing cat- 



