BAIRD'S SPARROW 757 



two species are not particularly closely related. Ammodramus savannarum 

 appears to complete its molt before migrating, but this is difficult to prove. Be- 

 cause of the much broader range of savannarum, migration of juvcnals in this 

 species can be proved only through banding. 



In both species of Ammodramus there is a precocious development of winter 

 plumage in the scapular region of the upper back, but the bulk of the juvenal 

 plumage is retained until well after the first flight feathers are grown. Sutton 

 (1935, 1937) discussed the development of the juvenal plumage and the early 

 stages of the post juvenal molt in savannarum. D wight (1900) described the molt 

 of this species as complete, and mentioned a partial prenuptial molt (spring) 

 involving mainly feathers of the head and anterior portions of the body. There 

 is a similar spring molt in A. hairdi, as indicated by the only adult specimen at 

 hand, but I have found no published data on the molts of this species. 



The nearest allj' of Ammodramus is probably Passerherbulus henslowi. The 

 three species are similar in habitat, and all have a scaled back pattern in juvenal 

 plumage. Their molts are similar, so far as I know. The underparts of juvenal 

 Passerherbulus are immaculate, of juvenal Ammodramus, streaked. 



T. M. Shortt (1951) compares the juvenal plumage with that of 

 2 other species : 



A circumstance that struck me forcibly while collecting specimens of juvenile 

 birds in the prairie region of Manitoba was the similarity in juvenal plumage of 

 three species of birds, representing two families, that were closely associated on 

 the nesting grounds. I refer to Sprague's pipit, Anthus spragueii, Baird's sparrow, 

 Ammodramus hairdii, and chestnut-collared longspur, Calcarius ornatus, all of 

 which have a "scaled" pattern on the dorsal area. This was considered somewhat 

 remarkable, especially since the "scaled" juvenal plumage is not common among 

 the Fringillidae and since another species of Calcarius (C lapponicus) has the 

 dorsal surface streaked. 



The implication seemed to be that there may be some survival value in a 

 "scaled" dorsal plumage for prairie-nesting passerine birds, though why it should 

 be more advantageous than a streaked plumage is not obvious. 



T. S. Roberts (1932) gives the following description of the adult 

 phmiage : 



Top of head and nape a rich, strong buff or brownish-yellow, striped with black, 

 especially on sides of crown and nape; sides of head and neck pale buff, more or less 

 flecked with black; a narrow line of black spots on side of throat; feathers of back 

 dull black centrally, margined with grayish-white or pale buff, producing a 

 streaked appearance; rump lighter, more buffy; underparts white or pale buff on 

 throat and breast; streaked on sides, flanks, and across breast with black, the 

 streaks on breast sharply defined and forming a necklace, those on sides more 

 diffuse and tinged with rufous; wing feathers greyish-brown, the coverts darker 

 centrally, all edged with pale rufous; 2 not very distinct wing-bars; tail dull brown 

 or blackish, the outer feather on each side narrrowly edged with white outer web 

 and pale, dull white terminally, suggesting a white outer tail-feathor when seen 

 by transmitted light; the other feathers narrowly tipped v.ith dull white or 

 buffy, bill light flesh color, darker at tip; legs flesh color, feet darker; iris brown. 



* * * The middle pair of tail-feathers is much narrower and more pointed 

 than the others. 



Two female adults, taken at Gardner Wash, Ariz., by R. Johnson 

 and P. J. Gould, Feb. 6, 1960, weighed 17.0 grams and 17.8 grams 



