10 Trans. Acad. Sci. of St. Louis. 



In years of drought during August and September, and such 

 years are by no means rare, migrants proceed southward on 

 their journey without much delay, because insect food of the 

 kind they like is scarce, and all birds need water for drinking and 

 bathing. The drying up of water courses and ponds has much 

 to do with the early disappearance of birds from their breeding 

 ground. The condition of our lakes and rivers governs the 

 occurrence and abundance of water-birds in autumn. Should 

 our rivers be so full as to cover all sandbanks and mud flats, 

 waders will not remain with us; on the other hand, ducks will 

 be rare when our ponds and sloughs are very low or dry, or when 

 the water is too deep for dabbling. The presence or absence of 

 particular species at certain seasons is therefore the direct result 

 of the great variation in the seasonal distribution of precipi- 

 tation. 



In winter, too, it is the abundance or scarcity of snow on th« 

 ground that regulates the presence of birds more than the tem- 

 perature does. Fortunately in most winters we cannot con- 

 plain of too much snow, though the average snowfall for tie 

 state is said to be eight inches in the southeast, and thirty inctes 

 in the northwest. First snows usually do not fall before ihe 

 middle of November; but here, too, the exceptions are almoss as 

 frequent as the rule. Snow once covered the ground at St. 

 Louis as early as November 5 and did not entirely disappear 

 from the north sides of houses until the middle of April (1381). 

 In another year (1889) there was no precipitation of any kind 

 during the entire fall and winter until the first of Jaiuary, 

 1890, when exceedingly heavy rain and wind storms folowed. 

 Snows falling before Christmas are usually light and drilled by 

 the accompanying cold and high winds. Such snows do not 

 affect bird life seriously, because they leave much groind un- 

 covered and accessible to the ensuing sunshine. The west kind 

 of snow, that which is introduced or followed by freeing rain 

 and sleet, falls mostly between the fifth of January andtenth of 

 February, generally in advance of our severest pohr waves 

 whose low temperature preserves the icy crust alnost intact 

 for days and weeks. They are naturally very destuctive to 

 bird life, the more so the further southward they exteid and the 

 longer they last. It was one of these periods that came near 

 exterminating our eastern bluebirds in February 185. 



The deepest snows fall in the latter part of wintr, from the 

 last of February to the first of April, but remain o the ground 



