132 IOWA ACADEMY OF SCIENCE Vol. XXV, 191S 



seasons the route used was covered by the same observer at the 

 same hour almost daily during the spring migrations, but be- 

 cause of press of other duties less extensively during the third 

 season. It would seem that with all factors as nearly equal 

 during each trip as it was possible to make them, the data secured 

 should furnish a fairly reliable guide to the migratory move- 

 ments of birds in this region. Once or twice a week trips were 

 made over this territory and up the river to and including the 

 Goose ponds. It was found that while more species would be 

 seen oai a single trip over the larger territory the number of new 

 arrivals was not likely to be increased much OA'er that obtained 

 from the more limited area. Some interesting results were ob- 

 tained from the more limited area. It was found that the num- 

 ber of species seen on a given day varied directly with the 

 length of time spent in the field. On the other hand two or 

 three hours in the early morning seemed to reveal as many new 

 migrants as the longer trips. This probably was due entirely 

 to local conditions. At this point the Iowa river valley is wide, 

 but the timber fringe comparatively narrow. As it is used to 

 the exclusion of any other migration line nea<r IMarshalltown. it 

 follows that a careful working of two miles of this timber belt 

 furnished almost as complete a list of the migrating forms as tb.A 

 more extended trip. The route followed each morning crossed 

 and recrossed this timber and the adjacent pasture lands at fre- 

 quent intervals, and to the best of my knowledge furnished a 

 reasonably accurate list of the birds occupying the territory on 

 that morning. On the other hand a trip covering. ten miles of 

 the river bottom offered opportunity to visit localities where 

 other species which were known to be nesting or lingering from 

 previous migration waves could be added to the day's list. One 

 phase of these bird movements brought out repeatedly during 

 the three season's observations was the tendency for a species to 

 appear in large numbers on a certain date and after slowly de- 

 creasing for several days, suddenly to increase in num])ers again. 

 The goldfinch, a common and noisy species, well illustrates 

 this point. These birds winter in small numliers but do not 

 usually become common before the last of March. In 1913 they 

 first appeared in numbers on March 31. On this date the species 

 was marked common, on April 1 tolerably common, on April 3 

 several, and on April 5 and 6 three individuals were recorded 



