ilooft J^etD0 anti 3^etotetofi^ 



The Migratory Movements of Uirds 

 IN Relation to the Weather. By 

 Wells W. Cooke. From Yearbook of 

 Department of Agriculture, for iQio, 

 PP- 379-390, I map. 



No one is better fitted than Professor 

 Cooke to discuss this ever-interesting 

 subject, and what he has to say in this 

 paper may be taken as adequately express- 

 ing our present knowledge. His "conclu- 

 sions" are as follows: 



"The foregoing facts show conclusively 

 that weather conditions are not the cause 

 of the migration of birds, but that the 

 weather, by influencing the food-supply, 

 is the chief factor which determines the 

 average date of arrival at the breeding 

 grounds. Migration is undertaken in 

 response to physiological changes in 

 birds, and the date of starting, in the 

 case of most species, bears no relation 

 whatever to the local weather conditions 

 in the winter home. The weather encoun- 

 tered en route influences migration in a 

 subordinate way, retarding or accelerating 

 the birds' advance by only a few days, and 

 having slight relation to the date of 

 arrival at the nesting-site. 



"Local weather conditions on the day 

 of arrival at any given locality are minor 

 factors in determining the appearance 

 of a species at that place and time. The 

 major factors in the problem are the 

 weather conditions far to the southward, 

 where the night's flight began, and the 

 relation which that place and time bear 

 to the average position of the bird under 

 normal weather conditions. Many, if not 

 most, instances of arrivals of birds under 

 adverse weather conditions are probably 

 explainable by the supposition that the 

 flight was begun under favorable auspices 

 and that late in the night the weather 

 changed. Spring migration usually occurs 

 with a rising temperature and the move- 

 ments of autumn with a falling temper- 

 ature. In each case the change seems to 

 be a more potent factor than the absolute 

 degree of cold. 



(I 



"The direction and force of the wind — 

 except as they are occasionally intimately 

 connected with sudden and extreme va- 

 riations in temperature — seem to have 

 only a slight influence on migration. 



"Another conclusion, equally apparent, 

 is that neither time of migration, the 

 route, nor the speed of one species, can be 

 deduced from records of other species, 

 even though closely related; in other 

 words, each species, and even each group 

 of individuals of a species, is a law unto 

 itself."— F. M. C. 



A Biological Survey of the Sand 

 Dune Region on the South Shore 

 of Saginaw Bay, Michigan. Prepared 

 under the direction of Alexander G. 

 RuTHVEN, Chief Field Naturalist, Michi- 

 gan Geological and Biological Survey. 

 Publication 4, Biological Series 2; Lan- 

 sing, Mich. 8vo., 347 pages, 19 plates, 

 I map. 



This volume records the results of what 

 was evidently a biological survey in the 

 best sense of the term. Taking a well- 

 defined area where primitive conditions 

 existed, Mr. Ruthven secured the cooper- 

 ation of a corps of specialists, and we have 

 here, consequently, the observations and 

 conclusions of men who not only were 

 especially qualified for the particular 

 work in hand, but who had the inestimable 

 advantage of reporting on material which 

 they had collected themselves. Thus G. 

 H. Coons writes on the 'Ecological Rela- 

 tions of the Flora,' C. K. Dodge, gives 

 a 'Catalogue of Plants,' H. Burrington 

 Baker reports on the Mollusca, A. Frank- 

 lin ShuU on 'Thysanoptera and Orthop- 

 tera,' Charles A. Shull and M. A. Car- 

 riker, Jr. on 'Mallophaga,' A. L. Leathers 

 on 'Fish,' Alexander G. Ruthven on 

 'Amphibians and Reptiles' as well as on 

 the general biological problems of the 

 survey; N. A. Wood on 'Mammals' and 

 the same author with Frederick Gaige 

 gives a well-annotated list of the 128 

 species of the birds observed. The whole 

 undertaking embodies exactly the kind of 



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