454 ANIMAL LIFE IN THE YOSEMITE 



a meadow in Yosemite Valley, or by a stand of smallish lodgepole pines 

 on the edge of Tuolumne Meadows. In other words, the Chipping Sparrow 

 is to be found in almost any climate, providing its special associational 

 needs are met. Here is a case, then, where character of habitat (niche) 

 weighs more in the economy of existence than do the factors of climate. 



The chipping sparrow population is not uniform throughout its wide 

 range but varies in the different zones. The birds are perhaps most numer- 

 ous in the Transition Zone and least common in the Lower Sonoran and 

 Hudsonian zones, A continuous census along the Tioga road between 

 Porcupine Flat and Snow Flat, on June 28, 1915, revealed one or two 

 birds an hour. About this same number an hour was noted in the Upper 

 Sonoran Zone at Pleasant Valley in May, 1915. In the Transition Zone, 

 in Yosemite Valley, the average was six or more, seen or heard, in an 

 hour's census. 



The Western Chipping Sparrow arrives in the Yosemite section in 

 April or May, and leaves by late September or early October (the 7th 

 in 1920 [C. W. Michael, MS]). A few winter at Snelling where one was 

 collected January 9, 1915, from a flock of about 20 in company with some 

 Sierra Juncos. But the host which fills the foothills and mountains in 

 summer-time spends the winter somewhere to the southward, either on 

 the deserts of southeastern California or beyond, on the tablelands of 

 Mexico. The birds arrive in April, as nest building was already in progress 

 in Yosemite Valley on April 30 (1916) ; and individuals were well estab- 

 lished in the foothills between Lagrange and Coulterville on May 9 (1919), 

 Occupation of the higher mountains seems to be accomplished with little 

 if any delay. By May 24 (1919) the species was well established at Tama- 

 rack Flat (altitude 6400 feet). Near Mono Lake on May 6 (1916) chip- 

 ping sparrows were passing in migration, but they were not found there 

 later that season. The return migration sets in during September, and 

 by the end of that month most of the birds have gone. The last to be 

 reported in Yosemite Valley were seen on September 29 (1917) (Mailliard, 

 1918, p. 16), Our latest record for anj^ point above the level of the San 

 Joaquin Valley is for October 7 (1914), when a few were noted at El 

 Portal, 



But little time elapses after their arrival in the spring before the 

 chipping sparrows settle down to nesting duties; yet not all the birds 

 complete the rearing of their broods at an early date. Pairs engaged in 

 caring for eggs or young are apt to be found at almost any time up until 

 early July, Our earliest record of nest building is for April 30 (1916), 

 and the latest, of young still in the nest, was made on July 15 (1920), 

 Probably the bulk of the birds in the Transition Zone and above begin 

 nesting between the middle of May and the middle of June. At the higher 



