NATURE'S CALENDAR 87 



MAY 



As April was the month of migrating j^ay i 



fishes, so May is to be regarded as the 

 month of migrating birds throughout the 

 middle parts of the United States. In 

 the case of the fishes the coming seemed 

 regulated chiefly by the matter of tem- 

 perature — none arrived anywhere until 

 the water had reached the right degree of 

 warmth. The coming of the birds, how- 

 ever, seems to depend mainly upon the 

 matter of food. The great body of bird 

 migrants from the South must not reach 

 the northern districts until nourishment 

 has been prepared for them. As, how- 

 ever, the insect food, upon which most 

 land birds depend, at this season in par- 

 ticular, cannot itself develop plentifully 

 until vegetation has advanced to a certain 

 stage, and as this is dependent largely 

 upon warmth, we may say that tempera- 

 ture finally rules here also. 



May is a month of uncertainties in the 

 Northern States— the English April ; but 

 under its warmer suns the buds and 

 leaves struggle steadily against adversi- 

 ties and crowd forward. The grasses and 

 weeds have already made good headway ; 

 and the fruit-trees, most shrubs, the ma- 



