I20 



Bird - Lore 



regular in their appearance 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, Blackbird, Canada Geese, Meadowlark, 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, if food were always equally abun- 

 dant and if there 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, under normal conditions, is just as 

 regular as the pulsing of the heart and records 

 time as accurately 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. Because of this, the 

 male birds arrive first and are followed by the 

 females and later by the immature birds. 

 With some species, like the Robin, Bluebird, 

 and Phoebe, there is very little difference in 

 the time of arrival, but in the case 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 secure 

 a nesting-area that will not be overcrowded, 

 for once the male has established himself — and 

 it is often at the same spot year after year — - 

 he drives away all other males from the vici- 

 nity, awaiting the arrival of the females, and 

 particularly his mate of the previous year. 

 But with the later migrants, such as the shore-birds, that have a long way to go, the 

 females usually arrive with the males, and, with some species, courting takes place en 

 route and they arrive at the breeding-ground fully mated and ready to nest. 



The early migrants are those that have spent the winter entirely within the United 

 States. This is true of all the March birds in the northern states, but, during the last 

 of the month, the first birds from the West Indies and Mexico begin to arrive in the 

 southern states. About the middle of April, many of the birds that have wintered still 

 further south begin to arrive, including the Swallows, the Spotted Sandpipers, the Black 

 and White Warbler and the Water-Thrush. The last of April and first of May brings 

 even to the northern states the initial wave of birds from Central America, and perhaps 

 even northern South America, and about the middle of this month, when occurs the 

 height of the migration, thousands of tiny Warblers, Vireos, and Flycatchers that have 

 been wintering on the slopes of the Andes or the pampas of Brazil, are winging their 

 way overhead to Labrador, Hudson Bay, and Alaska. The shortest route which one 

 of the last to arrive, the Blackpoll Warbler, may traverse is 3,500 miles, while those 

 which nest in Alaska travel over 5,000 miles. Some of the shore-birds, which bring up 

 the close of the migration in late May or early June^ have undoubtedly come from Chile, 



THE SCREECH OWL A PERMAiNEM 

 RESIDENT 



