The Bird Department 



By a. a. Allen, Ph.D. 

 Assistaut Professor of Ornithology, Cornell University, Ithaca, N. Y. 



AUTUMN BIRDS AND THEIR MESSAGE 



No phenomenon of nature is more striking to the 

 observant watcher as he enters the September 

 woods than the change that has been wrought 

 in the realm of birds. The hundreds of shrill voices that 

 claimed his attention during spring and summer are now 

 hushed and he hears only the occasional notes of a red- 

 e\ed vireo or a wood pewee. So quiet are the tree-tops 

 and so silent the forest floor that he is almost ready to 

 believe that the birds are 

 gone, but, as he traces the 

 border of the woods fur- 

 ther, he suddenly finds him- 

 self in the midst of a flock 

 of birds even more numer- 

 ous than the hosts of 

 spring. Tliey are scratch- 

 ing in the leaves, shaking 

 the bushes and weeds and 

 chippering in the tree-tops 

 in such manner as to an- 

 nounce their presence be- 

 yond any doubt, although 

 they be difiicult or even 



impossible to see. 



In the fall the birds are 



no longer scattered evenly 



through the woods and 



fields but have gathered in 



flocks, sometimes many 



sipecies together, and are 



moving slowly southward. 



\Miere food is abundant 



they stop for some time, but 



they shun all places where 



food and water are scarce. 



In spite of their numbers, 



however, they are diflicult 



to see among autumn greens 



and browns, for the famil- 

 iar liveries of spring have 



been discarded for suitable 



travelling attire. Little 



change has come over the 



sparrows and vireos, whose 



dull plumages serve for 



both summer and winter, 



but the bright tanagers, 



buntings and warblers have 



now assumed the modest 



dress of the females and 



even the robin has his red breast tinged with gray. Let 

 us see, then, what has been happening during the past 

 few weeks to work these remarkable transformations. 



August is the month of molting, the season when birds 

 change their faded, worn plumage for fresh feathers, 

 often of a different color. The process, however, is such 

 a gradual one that, although every feather is shed and 

 replaced, one scarcely knows that it is taking place unless 



there is a change in color 

 as well. Beginning always 

 at a definite feather, usu- 

 ally the innermost primary 

 wing feather, the molt pro- 

 ceeds with regular sequence 

 until all the feathers are re- 

 placed. The second feather 

 is not lost until the first is 

 partially grown, and, be- 

 fore the third and fourth 

 are lost, the first is practi- 

 cally matured. The same 

 is true of the tail feathers, 

 so that a bird is never with- 

 out the use of its locomotor 

 organs and steering gear. 

 An exception to this rule 

 is found in the ducks and 

 diving birds which are not 

 dependent upon their wings 

 to escape their enemies and 

 which, therefore, can safely 

 molt all of their primaries 

 at the same time and be 

 temporarily deprived of the 

 power of flight. On the 

 bird's body, likewise, the 

 molt proceeds gradually 

 from a definite point, only 

 a few feathers being lost 

 at a time. The half -naked 

 chickens seen in many farm 

 yards are examples of 

 arrested feather develop- 

 ment which does not occur 

 in nature except in cases of 

 disease. As almost every- 

 one knows, feathers are not 

 born indiscriminately over 

 a bird's body but along defi- 

 nite lines called feather 

 537 



A SERIES OF MOLTIXG SPARROWS' WINGS 



Showing the way in which the feathers are replaced, beginning with the inner- 

 most primary (IX) and working gradually each way. Roman numerals indicate 

 primaries, arabic. secondaries. The arrows indicate the progress of the molt. 



