This report was posted to the email list of the Minnessota Ornithologists' Union by Karl Bardon, an excellent birder in Duluth. He does bird counts during spring and fall migrations for the Hawk Ridge Nature Center. The bird movements discussed occurred on April 12. This report has some age, but it shows the massive number of birds that can be on the move on a given day. Migration is in its early stages here. Be alert.

Bardon's report:

There was a mass migration event along the Duluth-Superior lakeshore on Sunday
April 12th, including 34,000 American Robins, plus smaller numbers of Rusty
Blackbirds, Common Grackles, Pine Siskins, Purple Finches, and Northern
Flickers (low hundreds of each), and a few Common Redpolls, Yellow-rumped
Warblers, and Yellow-bellied Sapsuckers. Although I have seen migration of
this magnitude in fall, this day was so amazing because all the birds were
so low and close, at tree height, with a continuous river of songbirds from
sunrise until nearly noon. Raptor migration was equally impressive with
1083 Red-tailed Hawks counted including 9 dark morph Westerns, plus 676
Sharp-shinned Hawks, 442 Turkey Vultures, 158 Bald Eagles, 24 Rough-legs,
12 Northern Harriers, 3 American Kestrels, 2 Merlins, 1 Peregrine Falcon, 1
Osprey, 1 Northern Goshawk, and 1 Swainson's Hawk. With two successive days
of very strong south winds, this is probably the best landbird flight I
have ever seen here in spring:). Smaller numbers (but still impressive)
continued on Monday (eg, over 5,000 robins and 289 flickers).