386 ANIMAL LIFE IN THE YOSEMITE 



Superintendent, have, for a number of years, carried on a campaign for 

 the reduction of the Blue-fronted Jay, more particularly in the Yosemite 

 Valley itself. Sixty-seven jays were killed in the midwinter of 1915-16, 

 in the ^dcinity of the government stables where they kept drifting in after 

 the arrival of the winter snow. A 3-hour census by the junior author 

 in this neighborhood a little later the same winter (February 28, 1916) 

 did not reveal the presence of a single jay there; in fact none was seen 

 on the floor of the Valley during a three day visit at that season. But by 

 the end of April the same year jays were again present in fair numbers. 

 And three years later, in 1919, even though the campaign against these 

 birds had been continued with greater or less persistency during the inter- 

 vening period, we could not see that their numbers on the floor of Yosemite 

 Valley were below normal. 



Some figures, even though somewhat speculative, will be suggestive 

 here. The floor of Yosemite Valley, counting the area below the 5000-foot 

 contour, contains roughly 10 square miles. Upon the basis of our many 

 censuses, we estimate the jay population in early spring, before the advent 

 of the new broods, to be 32 birds to a square mile, or a total of 320 jays 

 for the area in question. This, be it noted, is the population at the time 

 of year when the numbers have been reduced by various natural causes 

 to the lowest figure. With the breeding season, assuming that each pair 

 of adults successfully rears three young, the jay population jumps to 80 

 a square mile' or 800 for the Valley, an increase of 250 per cent ! Because 

 the surrounding territory was a reservoir of reserve jay stock, depletion 

 of the jay population locally on the floor of the Valley, in the campaign 

 described above, was quickly followed by a 'spilling in' of birds from 

 the flats adjacent and the slopes above. The pressure of competition for 

 food between the individuals of the species serves under normal conditions 

 to keep the birds spaced out rather uniformly. Whenever the population 

 is suddenly reduced in one particular place, birds from the surrounding 

 territory, beginning to feel the release of pressure, work in, and soon fill 

 the vacancy. The process is somewhat analogous to bailing grain out of 

 a bin; the 'hole' is quickly filled up. 



However much we may deplore the ravages of these jays among the 

 woodland songsters, it seems unlikely that any great or permanent reduc- 

 tion in the numbers of the former can be accomplished through human 

 agency, commensurate, at least, with the cost involved. The species is 

 well able to recover quickly from any local reduction, as has been shown 

 so well in Yosemite Valley. The Blue-fronted Jay is resident over a large 

 stretch of territory but sparsely occupied by man ; it soon becomes ' gun 

 wise'; and it is very secretive in its nesting habits. All these factors 

 appeal to us as making reduction hopelessly difficult. Furthermore, the 



