676 



SCIENCE 



[Vol. LVI, Xo. 1459 



and a peculiarly wet and tliick snowstorm that 

 occurred during the night of the thirteenth is 

 thought to have overwhelmed the birds when 

 in flight high overhead, soaking their plumage 

 and dazing them. At any rate, great numbers 

 hit the ground with fatal violence. In the 

 morning dead and injured birds were to be 

 seen over a wide stretch of country; on the 

 frozen surfaces of two lakes 750,000 dead long- 

 spurs were counted, by .the method of laying 

 off sample units of area and checking the birds 

 to be seen on these units. But in spite of this 

 spectacular destruction of individuals the Lap- 

 land longspur was not reported the following 

 years in the winter range of the species (Kan- 

 sas, etc.) as obviously less numerous than 

 usual. Did not the ability of the species to 

 recover from this extraordinary calamity rest 

 in the "factor of safety"? 



There is good reason to believe that release 

 of intra-speciflc pressure on the breeding 

 grounds of a species ds accomi>ajaied by greater 

 productivity on the part of the remaining pop- 

 ulation. The sun'ival chances for the young 

 are greater where the safest type of nesting 

 places is available to all the adults seeking to 

 breed, and where congestion of population, and 

 consequent drain on available food supply, has 

 been relieved. Also, towards the end of the 

 year, w^hen the annual pinch of food scarcity 

 comes into play, in the winter range, a larger 

 proportion of maturing individuals than usual 

 will survive. In other words, from one point 

 of view, calamitous reduction of population 

 benefits the immediately oncoming generations. 



Let me center attention now upon the sig- 

 nificant fact that certain of our birds are, and 

 always have been, totally wreprotected by either 

 law or sentiment — jays, crows, linnets, shrikes 

 and blackbirds. The iiate of annual increase 

 in those species is no different, in so far as I 

 am aware, than it is in the vireos, warblers, 

 mockingbirds, tanagers, and purple finches, 

 which latter are looked upon as desirable song- 

 birds. Yet the former are holding their own 

 just as well as the latter, protected, species. 

 Their numbers are always kept up to top- 

 notch commensurately with the prevalence of 

 their niches. They have reached the maximum 



population possible to them, consistent with 

 the nature of the country, and they hold to it. 



We all know of the enmity of orchardists, 

 and agriculturists, and spoi'tsmen toward 

 linnets, blackbirds and blue jays, respectively. 

 Now and then, and there is a case on record 

 as far back as thirty years ago, "blue jay 

 hunts" are held; in one lately recorded in- 

 stance, at Hollister, San Benito County, 1,531 

 California jays were killed in one day, in a 

 prize competition for the destruction of so- 

 called "vermin." Incidentally, yoTi will note 

 that sportsmen feel particular animosity 

 toward any competitor or rival in their own 

 field! They are right after anything that can 

 be called "vermin" from their standpoint. As 

 far as we can see, as a result of such cam- 

 paigns — shooting of blue jays, netting of black- 

 birds, and poisoning of linnets — there has been 

 only a very temporary and local reduction in 

 the numbers of these birds; two or three sea- 

 sons bring them back to normal : that is, to 

 the maximum numbers which the amplitude of 

 their respective niches will warrant. 



Bird population, in kind and quantity, is 

 controlled primarily by conditions of habitat. 

 It is a matter of food and shelter. The natural 

 history collector, as a factor against birds, is 

 only an exceedingly minor influence, one which 

 like all the others, is allowed for by the "factor 

 of safety." My readers will begin to suspect 

 that I have become sensitive because of the 

 inveighing that certain well-meaning but unin- 

 formed people have undertaken against the 

 killing of birds for specimens. I admit the 



score. 



Joseph Geinnell 



MusETJM OF Vektebrate Zoologt, 

 Universitt of California 



ARE PERMANENT DISTURBANCES 

 OF EQUILIBRATION INHERITED? 



The writer of this note has just brought to 

 completion a long series of studies upon the 

 jnechanics of equilibration in the white rat. 

 During the course of these studies certain facts 

 appeared which, though incidental to the orig- 

 inal problem, may be of importance in the 



