A Sfxond Bird Survey 35 



pected and extraordinary combination of circumstances made 

 this time exceptionally favorable for birds. 



Weather conditions on this day were almost ideal. The 

 air was clear, with 90 per cent of possible smishine ; a rela- 

 tive humidity of 62 at 8 a. m., and of 31 at 8 p. m. ; a baro- 

 meter ranging from 29.85 at 8 a. m. to 29.69 at 8 p. m. ; and 

 with a light south breeze in the morning, changing to a rather 

 strong northwest wind in the evening. The temperature also 

 was favorable, being moderately cool and equable, ranging 

 from a minimum of 42° at 5 a. m. to a maximum of 68° at 

 4 p. m. Thermometer readings at other hours of the day 

 were as follows : 4 a. m., 44° ; 7 a. m., 46° ; noon, 64° ; 2 p. m., 

 66°; 6 p. m., 65°; 9 p. m., 57°. 



The results of this all-day trip were as remarkable as they 

 were unexpected, for on the previous day the prospects were 

 far from bright. The total number of species observed by all 

 the parties collectively was 166, which is, so far as we are 

 aware, the largest number ever reported in a single day at 

 any locality in the United States, even by the combined efforts 

 of several observers. The total number of individual birds 

 noted was 17074. The reasons for this rather astonishing 

 result are not far to seek. The very cool weather of April 

 and early May induced the winter residents to remain late, and 

 at the same time greatly retarded the northward movement 

 of the later migrants; a condition which, to judge by the re- 

 ports of heavy spring migration from many other locilities, 

 obtained over much of the northern and middle portion of 

 the eastern United States. An examination of the appended 

 table will show that, while a large number of species was 

 present, there were only a few individuals of many of the 

 later migrants on this May 11, on which date the spring mi- 

 gration about Washington is ordinarily at its height. In 1917, 

 however, the high tide of the migration was not reached until 

 May 17 to 23, nearly ten days later than usual. On the other 

 hand, in 1917, some of the early migrants and winter resi- 

 dents were very numerous for so late in the season ; as, for 

 instance, the red-breasted nuthatch, blue-headed vireo, and 



