258 Union Bay 



study altitudes in which migration was conducted, whether 

 it was by day or night, whether the birds fed as they flew, 

 whether their flight was hurried and conducted on the en- 

 ergy of the fat which they had stored previous to the start 

 of the trip. 



The progress of science has altered these conditions. Much 

 research has been done in the field and the laboratory. The 

 data thus obtained have been checked and rechecked. The 

 results of widely scattered workers are continually being con- 

 solidated. Information formerly known only to the man who 

 had gathered it is now available in manuscript or printed 

 form or in lectures and is constantly put to use. Special 

 monographs on the physiology, anatomy, and histology of 

 one bird are often available. Lengthy life histories of species 

 have been prepared. Arthur C. Bent's Life Histories of North 

 American Birds already includes eighteen volumes and sev- 

 eral more will be required to complete the series. The litera- 

 ture of ecology and of all kindred subjects has increased 

 rapidly. 



In terms of the four swallows which nested in the marsh, 

 this means that it is no longer necessary, as in the early days 

 of field watching, to rely solely on one's own experience and 

 to suffer from the lack of it. Comparatively speaking, the life 

 histories of the swallows are fairly complete so that, for ex- 

 ample, I can obtain from the available literature such details 

 as range, winter residence, migration and arrival dates, 

 plumages at different ages and seasons. I was astonished to 

 learn that the cliff swallow, which I had known only in a 

 more or less local manner, actually ranges over much of 

 North and South America, going as far north as Alaska and 

 as far south as Argentina. I can compare my own nest ob- 

 servations with those of others living in widely separated 

 places who have also investigated location, speed of build- 

 ing, material used, number of eggs in the nest, and variation 

 in marking. I pick up information on the time when the eyes 



