Hi all - on Sunday, 5/21 I posted the following short note about seeing a migrating band of Blue Jays...
I got a LOT of replies, and I apologize for not compiling these sooner. (I hope I recaptured every one of these)
Spring
Migration across range is concentrated in late Apr-late May. Rarely, flights reported in Jun and early Jul.
Migration is much less conspicuous in spring than fall in Florida, with jays observed moving north numbering in the tens from late Mar through Apr. In Arkansas, occurs from mid-Mar through mid-May, with a peak in the second half of Apr. Spring flocks usually <30 birds, although >1,000/h were counted on 23 Apr 1960. In Missouri, movements most conspicuous from mid-Apr to late May, with peak during the last week of Apr and first week of May, when several hundred may be seen in a day.
In Illinois, spring migration is less tied to physiographic features such as rivers than is fall migration, and jays are more common in upland forests than in flood plain forests in the Upper Mississippi River. Early and late dates from Illinois are 14 Mar and 26 May, respectively. High counts of up to 800/h fall from 18 Apr to 2 May in the southern two-thirds of the state, and from 1 to 21 May in the north.
In Ohio, migratory movements are more conspicuous in spring than fall, but this effect is in large part the result of migration along Lake Erie. Flocks of 5-30 individuals are most common in interior counties, but along the lake counts of 200-700/h is typical, with flights of 1,000-2,000/h and estimates of 5,000-10,000/d recorded. Migration begins 15-22 Apr and continues through 3-10 Jun . Blue Jays migrate north across Lake Superior into s. Ontario.
In Maryland, earliest arrival was 14 Apr, migration peak 21 Apr to 6 May, and latest departure 18 May. At Cape May, NJ, migration is much less spectacular in spring than in fall, with maxima around 100/d. Migration there is also considerably later than in the central U.S., with numbers peaking in late May and early Jun, and some apparent migratory flights observed in late Jun and early Jul. Spring migration is concentrated in May in Massachusetts, with daily counts reaching 300-500 not uncommon. Maximum count of 1,500 in 1 h on 22 May 1980; 300 counted on 1 Jun 1958.
There is also a helpful summary of Blue Jay migration in Maine with interesting historical specifics in Birds of Maine (Vickery et al), p. 408, for anyone who wants to start their day by weight-lifting this amazing and hefty reference!