104 U. S. NATIONAL MUSEUM BULLETIN 211 



male is on her, probably a great deal of the weight is supported by 

 the material on which her breast is resting. The male does not main- 

 tain his balance in this position for more than a second, and prob- 

 ably the first attempt at copulation has been unsuccessful. He jumps 

 off, takes two or three short hops, and mounts the female again. 

 This may be repeated five or six times until finally it appears that 

 a successful copulation has taken place, because of the slightly longer 

 time (about 1% seconds) the male remains on the back of the female. 

 As many as 16 consecutive attempts at copulation have been counted — 

 all in rhythmical succession. The female remains in the same position 

 during the whole performance." 



Nesting. — Yellow-headed blackbirds nest in colonies, often of 

 very large size. The colonies are not as densely packed with nests 

 as are those of the tricolored redwings in parts of California, though 

 in the most thickly populated colonies as many as 25 or 30 nests may 

 be found in a space 15 feet square. The colonies are not always con- 

 tinous, and may be scattered in separate groups along the shores of 

 a lake or slough where the vegetation is most suitable for nest con- 

 struction. Red-winged blackbirds are usually more or less loosely 

 associated with the yellow-heads on their breeding grounds, but gen- 

 erally the two species occupy different portions of the marsh. The 

 nests of the yellow-heads are invariably built over water, preferably 

 from 2 to 4 feet deep and rarely much deeper. Should the water 

 recede during the process of nest building, unfinished nests found to 

 be over dry land are likely to be abandoned. 



The nest is built entirely by the female, without any help from the 

 male. In his study of a nesting colony in Minnesota, Roberts (1909) 

 gives the following good description of the construction of the nest: 



The body of the nest was invariably constructed of water soaked dead grass 

 blades picked out of the water of the marsh. This sort of material being soft and 

 pliable was easily woven and wound around the reed stems to the smooth sur- 

 face of which it closely adhered; and when the structure, which was at first very 

 wet, soggy and dark colored, dried in the sun and wind, it contracted and drew 

 the included reed stems nearer together thus forming a compact, firm, and securely 

 attached basket-like nest. The lining consisted of pieces of broad, dr}', reed 

 leaves and the rim of the nest was well finished off with fine branches of the 

 plume-like fruiting tops of the reeds. Occasionally the lining was not placed for 

 a day or two until the nest had dried somewhat, but usually the coarse lining was 

 added, in part at least, to the bottom and around the walls while the body of the 

 nest was still in course of construction and soft and wet. The finishing touches 

 to the nest consisted in adding the fine material about the upper walls and rim 

 which, in the more perfect nests, partially closed and formed a sort of canopy 

 over the entrance. 



These nests were all built in quill-reeds (Phragmites) , and were 

 placed from 2 to 3 feet above the water. Of the 62 nests started in 

 the colony, 28 were abandoned before completion, "due to faulty 



