36 U. S. NATIONAL MUSEUM BULLETIN 211 



five or six, and only one brood is raised in a season. Bendire (1895) 

 describes the eggs as follows: 



The eggs are ovate or short ovate in shape. The shell is close grained and 

 somewhat glossy. The ground color varies from pearl gray or pale ecru drab to a 

 pale reddish brown or pale cinnamon rufous. They are irregularly blotched and 

 spotted with different shades of claret brown, chocolate, heliotrope purple, and 

 lavender markings, intermingled with each other, and varying greatly in size and 

 intensity. Almost every set is differently marked, and it is extremely difficult to 

 give a fair average description. In some specimens the ground color is almost 

 hidden, the markings being nearly evenly distributed in the shape of large blotches 

 over the entire surface of the egg. In the majority, however, the darker markings 

 are mainly confined to the larger end of the egg, while the paler ones are more 

 noticeable in the middle and about the smaller end. 



The average measurement of seventy-seven specimens in the United States 

 National Museum collection is 21.08 by 15.71 millimeters, or 0.83 by 0.62 inch. 

 The largest egg in this series measures 22.35 by 16.26 millimeters, or 0.88 by 0.64 

 inch; the smallest, 17.53 by 15.24 millimeters, or 0.69 by 0.60 inch. 



William George F. Harris has in his collection a set of eggs larger 

 than any in the National Museum; these measure 23.9 by 16.2, 24.1 by 

 16.1, 23.9 by 16.4, 23.8 by 16.2, and 24.0 by 16.1 millimeters. 



Young. — The period of incubation for the bobolink is given by 

 F. L. Burns (1915) as 10 days, but Mrs. Wheelock (1904) says: "The 

 mother bird broods alone for thirteen days, while Robert frolics gayly 

 over the fields with others of his sex, always within call, but seldom or 

 never feeding her. When the young are hatched, however, he takes 

 charge of them, and I have found him alone with a brood of seven 

 nestlings huddled in a fence corner in Michigan." E. H. Eaton (1914) 

 says: "The young are hatched in about 11 days and develop very 

 rapidly so that they are able to take wing in from 10 to 14 days." He 

 probably means that they leave the nest at this age, for it is well 

 known that the young leave the nest and wander around in the grass 

 for several days before they learn to fly; at this stage many would be 

 killed by early mowing and raking. While still in the nest, the young 

 are practically invisible; packed in as closely as sardines in a box, they 

 show no form or shape, remaining absolutely immovable and with 

 eyes closed; and their colors match the surrounding earth so closely 

 that one could step on them without seeing them. Only when one of 

 the parents comes with food do they wake up and give the buzzing 

 food call. 



A. D. Du Bois has sent me some very full notes on the behavior of a 

 pair of bobolinks and their young, from which I can quote only a few 

 parts: "June 14 (midmorning) : All the eggs appear to have hatched. 

 The female jumps over the grass for a distance of three or four feet, 

 then hobbles along in the grass; and, if I follow her, she repeats this — 

 and continues to repeat until we are perhaps a hundred feet from the 

 nest, when she flies for a short distance. This is the pattern of her ruse. 



