It is interesting to see Ohio observers reporting some late occurrences this
year--not just a few isolated instances, as you might expect any year, but a
significant number of them: eastern phoebes, catbirds, snipes,
not to mention a tree swallow and a wood thrush persisting into January, are
examples.
	The weather has been screwy, no doubt. Early November was very mild, and
encouraged very late, even record late, stays by some perching birds. The
second half of November, and the first three weeks of December, were
uncharacteristically cold; since then, things have been uncharacteristically
warm. It would not be too far off to say we had January weather in November,
and November weather in January.
	On a larger scale, you cannot rule out global warming as a cause. 2005 was
the second-warmest year in the history of weather records, and 47 of the 50
States had warmer temps than usual. Atmospheric concentrations of a
greenhouse
gas like carbon dioxide are higher than at any time in the past 650,000
years,
according to glacial ice samples. It is quite possible this warming
influenced
the fall and winter climate here.
	Human influences like structures, plantings, and even ambient heat
encourage
birds to stay longer than they once did. Black vultures are less cold-hardy
than turkey vultures, yet large roosts now persist in Ohio, often because
they
huddle near chimneys on buildings. Artificial plantings attract late
hummingbirds and thrushes and mimids; a hundred years ago, all reports of
mockingbirds in northern Ohio were rightfully dismissed as escaped caged
birds.
	In general, many birds--more than the average person might think--are able
to
handle the temperatures of our latitude year-long. It is usually *not*
temperature that determines birds' ability to hang on in winter--their
feathers are superb at conserving body heat--but the availability of food.
Seed-eaters find plenty during winter here, barring snow and ice cover that
make food impossible to reach. Insectivores can also survive our winters.
What
drives birds to move south, or may kill them, is weather that eradicates
their
food sources--usually very deep snow or ice that seals off seeds or insects
or
other aquatic prey. Phoebes are adapted to making use of winter-emerging
insects like winter stone-flies, and so are tree swallows, the most
adaptable
of our swallows temperature-wise. Snipes, and maybe even woodcocks, can find
food in damp areas that stay unfrozen because of seeps and springs. All of
these conditions have prevailed in recent weeks, and have led to increased
sightings of these species.
	Another unrelated influence--harder to pinpoint, and this is only a
guess--is
yielding the larger-than-normal numbers of swans and geese we're seeing. As
for swans, mutes are resident in the usual numbers, and our introduced
trumpeter swans as always "migrate" only as far as they have to, but tundra
swans have been unusually numerous and widespread this winter. Maybe warmer
temps have induced them to linger, and reduced duck numbers may afford them
more forage than normal. Unusual numbers of geese---greater white-fronted,
snow, and Ross's geese (record numbers of the latter)--may have something to
do with displacements from the Mississippi flyway by strong western winds,
as
well as mild temps.
	These are all speculations, but thanks to so many careful observations from
the field we at least have something to speculate about.
Bill Whan
Columbus