January, 1922. 



The Canadian Field-Naturalist 



19 



The systematic and thorough manner in which 

 the life histories of the species dealt with are set 

 forth is indicated by the following quotation from 

 the Introduction to the "Life Histories of North 

 American Diving Birds": 



"After a few introductory remarks where these 

 seem desirable, the life history of each species is 

 written in substantially the following sequence: 

 Spring migration, courtship, nesting habits, eggs, 

 young, sequence of plumages to maturity, seasonal 

 molts, feeding habits, flight, swimming and diving 

 habits, vocal powers, behavior, enemies, fall 

 migration, and winter habits. An attempt has 

 been made to avoid repetition in dealing with 

 subspecies." 



The task which the author has thus outlined for 

 himself has, in general, been well performed. 

 Previous publications have frequently been drawn 

 upon for essential data and apt passages so that the 

 volumes summarize the knowledge already avail- 

 able in this field. Much original matter has also 

 been contributed, both by the author himself, who 

 has travelled far and wide to study North American 

 birds in their homes, and by a host of other 

 ornithologists, who have furnished notes and data 

 on particular points. Although the volumes thus 

 present admirable and strictly up-to-date accounts 

 of the life histories of the species considered, this 

 serves to emphasize the fact that our knowledge 

 of the life histories of many species is very unsat- 

 isfactory. Little or nothing is known about the 

 place and manner of the nesting of several 

 species, such as the Marbled Murrelet and the 

 gray-winged gulls (Kumlien's and Nelson's). 

 There is a very great deal for students of avian 

 life histories yet to accomplish. 



An important addition to the text in the second 

 volume is information regarding reservations and 

 the species which are protected in them. This 

 information hardly does justice to Canadian 

 reservations established under the Migratory 

 Birds Convention Act, but this may be due to the 

 fact that the manuscript for this volume was 

 completed a considerable time before the volume 

 was published. 



Several of the life histories in each volume are 

 contributed by Dr. Charles W. Townsend. 



The illustrations form a most pleasing and 

 valuable feature of these publications. Abundant 

 half-tone plates, depicting chiefly birds and birds' 

 nests in their natural surroundings, are scattered 

 through the text. Special colored plates, showing 

 in their actual sizes one or more typical eggs of 

 every species dealt with whose eggs are available, 

 are bound in each volume. These are of a very 

 ligh quality, especially those in the volume on the 

 lulls and Terns, which are on egg-shell paper and 



are beautiful examples of their kind. 



The author defends the Loon against perse- 

 cution, thus furnishing justification for the legal 

 protection now accorded to Loons in Canada and 

 the United States under the Migratory Birds 

 Convention. Speaking of the fact that the 

 Loon's diet of fish includes trout, he says, "Some 

 sportsmen have advocated placing a bounty on 

 loons on this account, but as both loon and trout 

 have always flourished together until the advent 

 of the sportsmen, it is hardly fair to blame this 

 bird, which is such an attractive feature of the 

 wilds, for the scarcity of trout. We are too apt to 

 condemn a bird for what little damage it does in 

 this way, without giving it credit for the right to 

 live." With these statements, which are capable 

 of a wide general application, the reviewer is in 

 hearty agreement. 



Mr. Bent speaks of the much-discussed soaring 

 flight of Gulls, saying "To my mind it is simple 

 enough to understand, if we can realize that a gull 

 is a highly specialized, almost perfect sailing vessel, 

 endowed with instinctive skill in navigating the 

 air to use the forces at its command to advantage. 

 With a clear knowledge of the forces at work when 

 a ship sails, close hauled, to within a few points of 

 the wind, we can imagine the gull sailing along a 

 vertical plane, in which the force of gravity re- 

 places the resistance of the water against the 

 keel and the wind acts against the gull's wings as 

 it does on the sails of the ship; the resultant of 

 these two forces is a forward movement, which the 

 gull controls by adjusting its center of gravity and 

 the angle of its wings." 



Although this analogy is plausible at first 

 glance, it will not stand investigation. There is a 

 radical difference between the action of the force 

 of gravity upon a soaring bird and the action of 

 the resistance of the water against the hull and 

 keel of a vessel sailing close-hauled. The resis- 

 tance of the water against a vessel always acts 

 directly to consume the component force making 

 for leeway, whereas the force of gravity acts upon 

 the bird's mass in a fixed direction, at right angles 

 to the force exerted by a horizontal current of air. 

 It therefore cannot prevent leeway, and, however, 

 the force of a horizontal wind may be divided into 

 components by the position of the soaring bird's 

 wings and body, the ultimate resultant of those 

 components must be such as to cause the bird to 

 move to leeward, not to windward. This fact can 

 be demonstrated readily by means of the usual 

 formal diagrams indicating resolution of forces, 

 the reproduction of which here would exceed the 

 limits of this review. 



The true explanation of the undeniable fact that 

 Gulls and other birds do soar against the wind 



