BLACK-HEADED GROSBEAK 487 



In late April and early May, soon after their arrival from the south, 

 the grosbeaks eng'age actively in courting. Sometimes two or even three 

 males will be singing and flying about in the vicinity of one female. Near 

 Lagrange on May 6 to 8, 1919, there was much frenzied chasing of females 

 by males and of rival males by one another. In some places it seemed as 

 though there was a surplus of males. The same conditions existed near 

 Coulterville on May 9 to 12; but by May 16 in Yosemite Valley, nesting 

 was well under way. Here, a female was seen gathering building material 

 on that date; on the 17th another bird had already completed her nest 

 and laid five eggs. At Pleasant Valley, in 1915, a brood of bob-tailed young 

 already out of the nest was seen on May 25 ; nesting in this instance must 

 have been commenced close to the first of May. Two nests with small 

 young were seen in Yosemite Valley on June 24, 1915. Another with the 

 male brooding one small youngster was seen there as late as July 29 (1915). 

 Hence nesting may commence about the first of May ; it is weU under way 

 by the middle of that month ; broods are emerging in numbers toward the 

 end of June, while a few pairs whose nesting program has been delayed 

 or interrupted are still busy with nestlings as late as the last week in 

 July. 



Nests of the black-headed grosbeak are placed in trees or large brushes, 

 usually at a height of not more than 12 feet from the ground. We have 

 record of several at approximately 8 feet, and others at 4, 6, 7, 15, 20, and 

 30 feet, respectively. Young black oaks, small incense cedars, mountain 

 lilac, apple trees, and chokecherry bushes, all had been used in instances 

 noted by us. A crotch, or a group of horizontal twigs, forms the usual 

 support, and the nest is frequently located against the main vertical stem 

 or trunk. The nest itself is an openly constructed affair, often little more 

 than a platform slightly concave above, and is so thin in weave that the 

 contents can be seen, at least in outline, from beneath. Sometimes the 

 nests are firmer and more cup-shaped than this usual type, although they 

 still exhibit the open-work style of construction. Small long plant stems, 

 grasses, and crinkly rootlets are the important structural elements. One 

 nest, rather deeper than the average, measured 5 inches across the outside 

 and 21/2 inches in height, while the interior was S^^ inches across at the 

 rim and about 1% inches deep at the center, 



A female was watched gathering nest material in Yosemite Valley on 

 May 16, 1919. She hopped about in a mountain lilac bush, finally selected 

 a small twig which, with a few pulls assisted by the cutting edges of her 

 mandibles, she broke off. Then she worked the twig along in her bill until 

 it was held across the middle. Still retaining the first twig, she gathered 

 a second in the same manner, after which she made off in irregular course 

 through the trees, en route to her nest. 



