During migration, you can rely on schedules worked out over the decades
to indicate when certain species are likely to be seen. Roughly, anyway.
There are a couple of resources on the Publications/Checklists pages of
http://www.ohiobirds.org/ of this kind: the Annotated Checklist shows
typical dates of arrival/departure across the calendar year; the Weekly
Checklist is a unique feature (based on the Annotated Checklist) that
shows chances of seeing all species probably present in any given
week--nifty to take along into the field.
        Of course, these represent only averages. Temporary factors like
weather systems can alter arrival dates and especially numbers, and
recent climatic changes are gradually exerting effects. You can learn to
read weather radar imaging to assess mass bird movements; in my opinion
this is far from predictive of what you will see in the field, but it
can help.
        The best information is reports from people who've been out in the
field, of course. This time of year there are several spots outside Ohio
that have reliably provided excellent premonitions of the Ohio migration
of, for example, waterbirds. Here are some:
        (1) Check the Indiana list for reports from Miller Beach. A map will
show you how little Great Lakes shoreline Indiana possesses. However,
this narrow southern end of Lake Michigan concentrates southbound birds,
and bird observers in a big way, and checking reports from this spot
gives an excellent snap-shot of lake movements. Jeff McCoy's reports
from yesterday there included all three scoter species and a
jaeger--surely a hint of what was to come here today.
        (2) Check the PA list for reports from Presque Isle. This spot is a few
miles from Ohio's eastern corner, where movements along the Lake Erie
shore have been well monitored and reported by folks like Jerry
McWilliams (his report the day before yesterday featured two scoter spp
and a jaeger).
        (3) Look into the SE Michigan list (two jaegers reported yesterday in
southern Lake Huron along with four long-tailed ducks), or the Ontario
list (brant, all three scoters), for other nearby areas of Lake Erie.
Lake Erie sightings from nearby states and Ontario will compose a
snapshot of movements, especially of young inexperienced birds headed
south to wintering areas in the oceans. Jaegers, for example, seem to
prefer to follow large bodies of water in fall migration, but when
they're headed toward the ocean from Miller Beach, some set off
overland, where they can be seen by sharp observers over inland
reservoirs along the way; others end up in Lake Erie headed east.
        Scoters showed up in southern Ohio for the first time this year this
morning. I bet some jaegers were missed along the Lake Erie shore, or
perhaps inland, too.
Bill Whan
Columbus

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