380 ANIMAL LIFE IN THE YO SEMITE 



abruptly at the Canadian-Hudsonian boundary, above which, is found the 

 Clark Nutcracker. On the east slope of the mountains, in the Yosemite 

 region, the Blue-fronted Jay is found only in the Canadian Zone. The 

 Transition Zone of the arid interior lacks at this latitude any extensive 

 growth of forest trees, and this fact probably accounts for the absence 

 of Blue-fronted Jays from that part of the Transition Zone. 



As a species the Blue-fronted Jay occupies the range outlined above 

 throughout the year, but with the coming of winter there is a down- 

 mountain movement (altitudinal migration) which carries a portion of 

 the jay population to lower zones. This has been observed on the west 

 .slope of the Sierras and may occur on the east side as well. At El Portal, 

 on November 28, 1914, an influx of Blue-fronted Jays was observed 

 immediately following the first fall of snow for the season on the adjacent 

 higher ridges. In 1915, on December 8, Blue-fronted Jays suddenly 

 appeared at Pleasant Valley. The jays stayed there "through the winter" 

 according to local testimony, but were gone by the end of February. 

 Mr. Donald D. McLean has told us that a certain number of these jays 

 regularly drop to below Coulterville for the winter months. In certain 

 winters, presumably those marked by severe storms in the mountains, 

 Blue-fronted Jays have migrated down even into the San Joaquin Valley, 

 for instance, to Stockton. It seems likely that difficulty in getting adequate 

 food is a more important factor in influencing this semi-migration than 

 unfavorable weather, especially since a certain number of the jays seem 

 to find no inconvenience in remaining in the higher zones throughout the 

 winter season. 



During the nesting season the jays are to be seen in devoted pairs, 

 and after the broods leave the nest the fullgrown young and their parents 

 remain for a time in family parties. With the coming of fall, the parental 

 and filial instincts wane, these family parties break up, and the individuals 

 scatter out rather uniformly through the forest. But the jays retain a 

 strong social sympathy which causes the separated birds to quickly congre- 

 gate about any object or sound which excites their curiosity. In mid- 

 winter, even this interest decreases and the jays then seem to pay little 

 attention to contemporary events, unless food be involved. Heightened 

 curiosity is, for birds in general, an accessory of the nesting season when 

 danger, apparent or real, threatening either the nest or brood, must be 

 guarded against. At the opposite season, midwinter, when nesting in- 

 stincts are at their lowest ebb, curiosity also lags. >S^e?/-preservation is 

 then the important factor. But even putting this seasonal variation aside. 

 Blue-fronted Jays show marked interest in most of the events which take 

 place about them. Often when the observer is seeking one of the rarer 

 or more reclusive birds or mammals of the forest, his cautious stalking 



