BIRDS AND THE WIND McMILLAN 361 



spring and goes south in our fall, carrying with it the doldrums, the 

 trade and antitrade winds, and the prevailing winds in both hemi- 

 spheres. Just as offshore and onshore winds or mountain and plain 

 winds are the effort of nature to equalize temperatures between ad- 

 jacent areas during night and day, so are monsoons an attempt to 

 balance the heat of the atmosphere over the seasons. Just as land 

 and sea breezes attain their maximum not at midday or midnight but 

 in the afternoon and early morning, so do the prevailing winds flow 

 fastest in spring and fall exactly in time with heaviest migration of 

 the birds. In a large-scale picture the two phenomena appear to fit 

 exactly. Will they also match when examined in detail ? The writer 

 believes that they will if we are careful to look at those details from 

 the viewpoint of the bird and not our own. 



There can be a wide difference in the two viewpoints. On the night 

 of September 8, the surface wind on the Atlanta airport was 3 miles 

 an hour out of the southeast, while the wind aloft from Washington 

 to New Orleans was out of the northeast quadrant of the compass 

 with an average velocity of 20 miles an hour. Wliile circling the 

 field, the writer turned on his landing lights to warn other pilots of 

 his position. At 900 feet off the ground, two small birds streaked 

 like meteors through the glare of the lights. At 700 feet a third 

 struck the under side of the fuselage with a pistol-like report. Three 

 birds do not make up a migration nor can it be proved that those 

 three were flying downwind. All that is certain is that the air was 

 moving southwest, that there were at least three birds in it, and that 

 a ground observer could have been ignorant of both facts unless he 

 had examined the weather map and the "winds aloft" report and 

 had been able to see the birds against the face of the full moon that 

 was shining. 



It is easy to add two and two although the sum obtained may not 

 be the correct answer. It is easy to conclude that migrants ride the 

 wind when birds are found going with it. Wlien it is known that 

 wind and weather are practically synonyms, it is easy to run through 

 "The Season" reports in Bird-Lore and change "cold weather" to 

 "northerly winds" and "warm weather" to "southerly winds" and be 

 pleased to see that migrants arrive with them. When one is looking 

 for just such a similarity it is easy to see the sameness between a map 

 of the migration routes and a map of the pervailing winds. Wlien 

 it is known from experience and study that an advancing cold front 

 crowds and lifts the warm air in front of it, it is natural to assume 

 that bird traffic should be crowded into a wave as automobile traffic is 

 jammed in a bottleneck, and find verification for this assumption in 

 the reports of watchers. To be conservative, it must be admitted that 



