Asked about this topic, I thumbed through the records available to me.
They confirm that Peterjohn (2001) is on the money when he says
Forster's terns "have returned by 25-26 March, and frequently appear
during the first week of April."
        Over the past decade, for example, there are a dozen published records
in the Ohio Cardinal on or before 12 April for the state (plus quite a
few others in the background, since generally only the first spring
record is published). There are two records for 25 March, in Muskingum
(1999) and Allen (2002) counties. There are Lake Erie records before 10
April from Erie, Cuyahoga, Lorain, Lake, and Lucas counties. Greg Links
reported one in Lucas County on 7 April 2001; on that same day,
Forster's were also seen in Lake (J. Pogacnik), Wayne (S. Snyder), and
Paulding (M&D Dunakin) counties.
        All of this is reflected in the "OBRC Checklist of the Birds of Ohio,"
available as the annotated version of the state list at
http://www.ohiobirds.org/publications/checklist/checklists.php  . A new
edition of this list is in preparation for later this year; it will be
in a larger format, incorporating extra data and new accepted Ohio
species, the most recent of which is a white-throated swift Aeronautes
saxatalis documented in Lucas County 2 April 2006.
        One last note, speaking of first arrivals. By 15 April last year (just
the day after tomorrow) we had Ohio reports of 18 warbler species!
They'll be here eventually...
Cheers to all,
Bill Whan
Columbus

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