The Bird Department 



By a. a. Allen, Ph.D. 

 Assistant Professor of Ornithology. Cornell Uniz'ersitv 



THE RETURN OF THE BIRDS 



IT is now nearly three months since the first horned 

 larks started northward over snow-covered fields. 

 Already they have their young on the wing and are 

 ready to start another brood ; yet there are many birds 

 that still have hundreds, even thousands of miles to travel 

 before they will reach their nesting grounds. The March 

 robin brought forth its crowd of admirers, the call of 



FOUR HUNGRY BABES 



A Louisiana water thrush feeding its young. This bird winters from 

 Mexico to Colombia and arrives in the northern United States 

 during the first of April. 



the bluebird drew a response from others, but now when 

 every hedge-row and thicket resounds with musical 

 voices and even the trees of the city streets flash with 

 brilliant warblers, everyone likes to stop and listen and 

 notice the unusual number of birds. And we cannot help 

 wondering whence have come these little wanderers, 

 where they are going, and what is the meaning of their 

 journeys. In great waves they come from the South, 

 flood us with beauty and song for a few days, and 

 then pass on. Wave after wave passes over us during 

 the course of the month until June arrives, when the 

 last immature birds hasten on to their nesting ground 

 and leave us with only our summer birds until the fall 

 migration shall 'bring them back once more. 



A little observation from year to year shows us that 

 these May birds are extremely regular in their appear- 

 ance and disappearance. One can soon learn just when 

 to expect each species, and if the weather is normal, it 

 will arrive on the day set. The earlier birds such as 

 the robin, bluebird, blackbirds, Canada goose, meadow- 



lark, and mourning dove, which come during March, 

 are much less regular because of the idiosyncrasies of 

 the weather. If there were no such thing as weather 

 and if food were always equally abundant; if it were one 

 great level plain from the Amazon to the Great Slave 

 Lake, the birds would swing back and forth as regularly 

 as a pendulum and cross a given point at exactly the 

 same time every year. For this migrating instinct is 

 closely associated with the enlargement and reduction of 

 the reproductive organs, a physiological cycle which, un- 

 der normal conditions, is just as regular as the pulsing 

 of the heart and records time as accuratelv as a clock. 

 With most species the organs of mature birds begin to 

 enlarge before those of birds hatched the preceding year, 

 and those of the males before those of the females. Be- 

 cause of this, the male birds arrive first and are followed 

 by the females and later bv the immature. With some 

 species like the robin, blueliird and phoebe, there is very 

 little diiiference in the time of arrival, but in the case 



A BANK SWALLOW 



Hovering over its burrow, these birds winter in northern South 

 America and arrive in northern United States during the last of 

 April. 



of the red-winged blackbird, often a period of two weeks 

 or even a month intervenes. This may be a wise provision 

 of nature to insure the selection of a nesting area that 

 will not be overcrowded for once the male has established 

 liimself, and it is often at the same spot year after year, 

 he drives away all other males from the vicinity, await- 

 ing the arrival of the females and particularly his mate 

 of the previous year. 



273 



