754 U.S. NATIONAL MUSEUM BULLETIN 237 part s 



Much has been said of the long searches necessary to the finding of 

 nests of this species. To point up this fact, an organized search of 

 one 350-acre field which harbored at least 30 singing males during the 

 first three weeks of July 1962, yielded only two nests of Baird's 

 sparrow. Over 100 man-hours of intensive search were spent in this 

 hunt, during which 15 active nests of other species of ground-nesting 

 birds were found, despite the lateness of the season. One nest in 1962 

 had a life history of just over one month — from a nest-scrape made 

 June 18, until the fledglings left the nest, July 21. 



Eggs. — Oliver Davie (1898) states: "The eggs are laid in June and 

 July and they range from three to five in number * * *." But 

 Cartwright et al. (1937) found the numbers varied from three to six 

 in the 15 nests they studied, with five eggs the average. They write: 



The ground color of the eggs is white, rarely showing a faint tinge of bluish. 

 Reddish-brown spots and blotches showing a decided tendency to form a wreath 

 about the larger end are the commonest markings. Occasionally there are small 

 black spots and lilac or lavender markings, the latter being probably due to the 

 obscuring of reddish- brown pigment by shell layers. The eggs are not easily 

 distinguished from those of the savannah sparrow, which are variable both in 

 ground color and markings, nor from those of the vesper sparrow, which they 

 closely resemble. They are larger than the savannah sparrow's and smaller than 

 the vesper sparrow's as a rule. 



Seven of the eight nests I found between 1960 and 1965 contained 

 four eggs as a full set; the eighth held five. The eggs of the first 

 two sets I found in 1962 were wreathed about the larger end; those 

 in the later nests were spotted more irregularly. 



W. G. F. Harris writes: "The usual set for the Bahd's sparrow 

 consist of three to five eggs. They are ovate and have only a very 

 slight gloss. The ground is grayish white, but this is frequently 

 obscm'ed by the numerous spots, blotches and speckles of 'auburn,' 

 'hazel,' 'chestnut brown,' or 'russet,' which often cover the entire 

 egg. Underlying spots of 'light Quaker drab' are discernible on 

 many eggs, especially on those which have less brown markings. 

 Occasionally, an egg will have a few spots of black. In many of the 

 sets I have examined, the spots and markings seem to be somewhat 

 dull or clouded. The measurements of 50 eggs average 19.4 by 14.6 

 millimeters; the eggs showing the four extremes measure 21.8 by 15.2, 

 20.3 by 16.3, 16.4 by 12.6, and 17.5 by 1S.5 millimeters." 



Incubation. — CartAvright et al. (1937) made the following observa- 

 tions on incubation: 



As mentioned in Table III, the duration of incubation has been found in one 

 instance to be eleven days. No other observations on this point are known to 

 exist. Incubation is performed entirely by the female, which leaves the eggs 

 only for brief periods, at nearly all times returning secretively by mousing away 

 through the grass. She is rarely seen during incubation except at the nest. 



