492 Recent Literature. [o"t. 



Nichols on Some Aspects of Migration. 1 — Those who are interested 

 in speculating upon the origin of bird migration will find much food for 

 thought in this short article of Mr. Nichols. Referring to the irregular 

 southward migrations of the Red-breasted Nuthatch and other species 

 of similar habit, he advances the theory that these movements are the 

 result of a great increase in abundance within the permanent range of the 

 species from which it then sweeps outward as it were in waves. We have 

 all noticed how few Nuthatches return northward in the spring following 

 an enormous autumn flight and Mr. Nichols explains this by the sugges- 

 tion that the bulk of them are utterly dissipated and lost, and that only a 

 small minority ever find there way back to their permanent range. This 

 type of migration he terms ' centrifugal,' and considers it to be the original 

 condition. Next comes the condition where the species has become so 

 adjusted to conditions as to maintain itself in unvarying though compara- 

 tively small numbers, here there is overcrowding and consequently no 

 migration at all. Then come species that retire from one part of then- 

 range to another during winter but never leave it entirely, simply adj usting 

 themselves to changed conditions; this is ' intraspecific ' migration; and 

 finally an extension of this condition where the winter and summer ranges 

 become entirely separated and the passage from one to the other constitutes 

 the ' centripetal ' migration so familiar in our spring and fall migrants 

 where " highly developed homing instincts in the individual bird take the 

 place of the futile centrifugal ' wanderlust ' of the race in its initial condi- 

 tion." 



The irregular movements of the Red-bellied Nuthatch and similar species 

 have always been a puzzle to students of migration and the failure of food 

 supply in their regular range never appealed to the reviewer as an adequate 

 explanation. Mr. Nichols' theory on the other hand has much to commend 

 it. 



While his last three conditions and the development one from the other 

 have been pretty generally recognized and will be generally accepted we 

 do not think that he has been very happy in the selection of the White- 

 breasted Nuthatch as an example of an absolutely resident species that 

 does not migrate at all. Certainly in many places familiar to the reviewer 

 it is much more abundant in autumn and winter than at other seasons. 

 It may indeed be difficult to find a species in which there is not some migra- 

 tory movement within its range. — W. S. 



Birds of the National Parks. 2 — Three of the National Park ' Circulars 

 of Information' for 1918 — those for Glacier, Sequoia, and Yellowstone 



1 An Aspect of the Relation between Abundance, Migration and Range in Rirds. Ry 

 J. T. Nichols. Science, August 16, 1918. pp. 168-170. 



2 General Information regarding Glacier Park, season of 1918 (birds, pp. 52-64); Ibid., 

 Sequoia and General Grant National Parks (birds, pp. 20-27); Ibid., Yellowstone National 

 Park (birds, pp. 61-66). National Park Service, Department of the Interior. Free on 

 application to the Director of the National Park Service, Washington, D. C. 



