I did some birding by bike in Montgomery County yesterday and today. I had some nice migrants both days though yesterday there was much more activity. 

Yesterday, 9/6, I biked in Rock Creek Park from North Bethesda to Lake Needwood. I made a quick stop at Dewey Local Park because I heard some tit activity. The highlight there was a Rose-breasted Grosbeak. Next I proceeded to my main destination: the stretch of Rock Creek Park roughly from Aspen Hill Rd to Southlawn Ln. In this section I encountered several big mixed flocks though not all with great diversity. Highlights were:

Veery
Nashville Warbler
Northern Parula
Chestnut-sided Warbler
Magnolia Warbler
Black-throated Green Warbler
BAY-BREASTED WARBLER
Black-and-white Warbler
American Redstart
Canada Warbler

I spent only enough time at Lake Needwood to realize there was not much in the way of food or water available. The highlight was one Baltimore Oriole. On the way home I stopped again at Dewey Local Park and found a singing Warbling Vireo.

Today, 9/7, I rode down to the canal. I started at Swain's Lock and made my way to just short of Violette's Lock and then back again. It was very slow, especially in the first few hours. On the way out the highlights were

Blue-winged Teal 
Green-winged Teal (2nd impoundment at Pennyfield, pointed out to me by Jim Nelson)
Black-throated Green Warbler
Scarlet Tanager

On the way back there was a brief period of activity when the sun was just coming out. I happened to be just northwest of the WSSC station (near Swain's Lock). This is where I had the real highlights of the day:

Warbling Vireo 
Northern Parula
American Redstart
Blackburnian Warbler
WILSON'S WARBLER
Indigo Bunting

Mike Ostrowski
North Bethesda