Vol i909" VI ] Recent Literature. 203 



are just dawning there, but when the foothills and plains below are becom- 

 ing dry and barren under the July heat, no longer productive of the food- 

 supply which they were in a condition to offer earlier in the season. I 

 believe these relative conditions prevail throughout southern California. 

 Without the mountains to accommodate the excess of bird population, which 

 could not be supported in late summer on the withered lowlands, we would 

 have fewer birds in the spring. The 'resident' species return to the low- 

 lands when the cold begins to reduce the food supply in the mountains; 

 and, what is also noteworthy, so do the 'summer visitants,' which thus 

 become transients for a few days in the fall as they pass back through 

 the lowlands on their way south, or rather southeastward. These latter, 

 therefore, undertake three distinct migratory journeys during the year: 

 from their winter habitat northwestward to their spring breeding-place, 

 from the latter up, and often northwards, to their summer feeding-grounds, 

 and then back down and then southeastward to their winter habitat." 



These well-attested facts have an interesting and important bearing 

 upon the general subject of bird migration, and especially upon the origin 

 of migration. As said later by Grinnell: "The geometric ratio of repro- 

 duction makes the population of a species an elastic quantity, expanding 

 into any favorable food area presenting itself. And the masses of different 

 species press against one another, like soap-bubbles, crowding and jostling 

 as one species acquires, through modification of food-getting powers and 

 perfected adaptability to other conditions, some advantage over another." 

 In this connection is discussed the mortality of birds and its causes, from 

 the standpoint of the author's observations in southern California. 



The report on the birds (pp. 50-54), like those on the mammals and rep- 

 tiles, consist of extensively annotated lists, relating to the habits and 

 local distribution of the species. The illustrations include a colored map 

 (plate i) of the life zones of the region, and a transverse profile, also in 

 color (plate ii), indicates both their vertical and horizontal extent. Most 

 of the remaining twenty-two plates are from photographs, and represent 

 types of vegetation and landscapes. — J. A. A. 



Grinnell on Birds of Southeastern Alaska. — "In the spring of 1907 

 a party was organized and outfitted by Miss Annie M. Alexander, for 

 the purpose of exploiting the fauna of certain islands. The party consisted 

 of Mr. and Mrs. Frank Stephens, Mr. Joseph Dixon, Mr. Charles 

 Littlejohn, and Miss Alexander herself, who headed the expedition." 

 The report on the work accomplished ' consists of nearly one hundred pages, 

 illustrated with two plates and a few text figures. The introduction and 

 the report on the birds are by Dr. Joseph Grinnell; the 'descriptions of 

 localities' are by Frank Stephens and Joseph Dixon; the report on the 



1 Birds and Mammals of the 1907 Alexander Expedition to Southeastern Alaska. 

 University of California Publications in Zoology, Vol. V, No. 2, pp. 171-264, pll. 

 xxv, xxvi, and text figs. 1-4. February 18, 1909. 



