NATURE'S CALENDAR 123 



crazy bobolinks, hovering over grass or June 3 



grain, are no wilder in their antics than 

 are the yellow-breasted chats that turn 

 somersaults above the roadside thickets. 

 Here and in the orchard are heard, in the 

 brisk morning air, the warbling of the 

 vireos, the clear carols of the two orioles, 

 the brilliant performance of the rose- 

 breasted grosbeak ; while close about the 

 house, as we step from the door to take 

 a look at the morning, our ears are 

 pleased with the exquisite voices of wren 

 and yellow-bird, vireo, chebec, blackbird, 

 and half a dozen other intimate friends. 



This singing of the birds in the spring 

 — and at no other season do they truly 

 sing, for the calling notes are different — 

 is an expression of their joyous excite- . 

 ment over this time of love-making and 

 domestic happiness. It is directed mainly 

 towards their mates, and is a part of the 

 display by which they seek to win and 

 keep them. Rivals sing against one an- 

 other, and sometimes these contests are 

 amusing to listen to, as, for example, 

 when the whippoorwiUs try to race one 

 another out of breath in their moonlight 

 chorus. There is good reason to believe 

 that this singing has been gradually en- 

 larged and perfected during past ages by 

 natural selection, just as the brilliant 

 dresses worn by many male birds have 

 been acquired in contrast to the plain 

 suits of their brooding mates. 



Why do birds choose this early part of 



