166 NINTH REPORT. 



SOME RECORDS OF THE FALL MIGRATION OF 1906. ^ 



Norman A. Wood. 



During the fall of 1906 the writer was permitted to spend the time inter- 

 vening between September 8 and October 16 at Portage lake, Washtenaw 

 County, Michigan, and during this time made notes bn the birds observed each 

 day. It seems advisable to publish these records for their bearing on the 

 fall movement of migrant species. 



DESCRIPTION OF THE LOCALITY. 



Portage lake is about sixteen miles northwest of Ann Arbor, Michigan, 

 and is situated in the "Interlobate Lake Region" which occupies the entire 

 region shown in the upper left hand corner of the topographic map known 

 as the "Ann Arbor Quadrangle." This region is made up of i^iorainic knobs, 

 lake basins, abandoned glacial drainage channels, and sand plains. The 

 hills are steep, the plains dry, and the lakes and swamps drain into the Huron 

 river which enters this region from the northeast. The Huron river and its 

 valley, with its old drainage channels, of which the most important is the 

 one at Ann Arbor, is doubtless an important migration route, and provides 

 a direct and easy route for the dispersal of southern river valley species. 



As the birds seem to follow this valley to some extent in their migration, 

 the situation of Portage lake is an esi)ecially favorable one for their obser- 

 vation, notwithstanding the fact that many species which use this route in 

 • the spring seem to pass to the east or west in the fall migration. On the 

 other hand many of the species which migrate in the sjii'ing too rapidly for 

 accurate observation may linger for days in the fall if the food and weather 

 conditions are favorable. 



My observations were particularly confined to the narrow triangular 

 shaped plain which separates Portage and Base lakes. This plain converges 

 from a width of one-half-mile nearly to a point at its lower or southern end, 

 where the outlet of Portage lake, which is about one-quarter mile below the 

 exit from Base lake, empties into the Huron river. The elevation of the 

 plain also descends towards this point which was evidently at one time under 

 water, as the soil is composed of marl and muck. Owing to the lowering 

 of the water level, however, the region is now much drier and overgrown 

 with willow, ash, elm and some soft maple. This- habitat, as determined 

 by almost daily observation, was apparentl}^ a favorite one for many of the 

 birds, especially Avarblers, vireos, thrushes and wrens. 



As before stated the plain rises gradually to the northward from the point. 

 Its soil on the higher parts is gravel and sand. On the eastern part of this 

 plain, at the present time, there are cultivated fields that extend to the 

 shore of Base lake; the western part is given up to an apple orchard of about 

 20 acres, with farm buildings at the northern end. On the west the orchard 

 extends to the edge of the plain which falls off steeply, 20 or 30 feet, to the 

 sandy beach of Portage lake.. This steep bluff is thickly covered with trees 

 of red and white oak, smooth-bark hickory and red cedar, the latter having 



1 From the University Museum, University of Michigan. 



