No. 602] SHORTER ARTICLES AND DISCUSSIONS 125 



mal as would eat the sort of food that any animal eats, and this 

 is an obvious impossibility for the meadowlark when we con- 

 sider such uncommon articles of diet as wood and petroleum. 

 Compared with many other birds, the meadowlark does use as 

 food a very wide range of plant and animal objects. This food, 

 however, is restricted to a particular habitat source, namely to 

 the meadow. The bird's entire equipment specializes it for 

 successful food-getting and for escape from enemies upon a 

 grassy plain or meadow. And it is a matter of common obser- 

 vation that its range is sharply delimited in most directions at 

 the margin of the meadow habitat, as where this is interrupted 

 by forest, brushland, marsh, rock surface or sand flat. This is 

 a conspicuous example of what we may call associational restric- 

 tion. But it is not the only way in which the meadowlark is 

 hemmed in. In this connection California again provides crit- 

 ical distributional evidence. 



We find meadowlarks occupying practically every appropriate 

 meadow, large and small, from the Mexican line to the Oregon 

 line and from the shores of the Pacific to the Nevada line, ex- 

 cept above a certain level on the higher mountains. In travel- 

 ing up the west flank of the Sierras, and this I have now verified 

 along three sections, meadowlarks cease to be observed at ap- 

 proximately the 4,500-foot level, and this in spite of the fact that 

 above that altitude meadows are found which are to all appear- 

 ances ideal for meadowlark requirements. I need only refer to 

 such seemingly perfect summer habitats as Monache Meadows 

 and Tuolumne Meadows. And though, in the winter these 

 would be uninhabitable, so are other meadows (as those in the 

 Modoc region, for instance), which are in summer warm and at 

 that season abundantly inhabited by meadowlarks. By the elim- 

 ination then upon proper grounds of various factors from the 

 list, we have left only three possible factors in this upward de- 

 limitation, namely, decreased atmospheric pressure, decreased 

 air density and decreased temperature of the summer season. 

 Since meadowlarks exist at corresponding altitudes in the warmer 

 though elevated Great Basin region, and since it has been pos- 

 sible to eliminate positively and in a similar way the first two 

 factors in the cases of many other birds and mammals, these fac- 

 tors are presumably without influence on the meadowlark; and 

 there is left but one— temperature. 



Within the state of California, meadowlarks, without the 



