Date: 1/30/18 5:14 pm
From: John Fussell <jofuss...>
Subject: Do feeders keep hummingbirds from migrating south in the fall?
Recently on this listserv there was a bit of discussion about whether
feeders keep hummingbirds from migrating south in the fall. This discussion
was prompted by reports, including mine, of mortality/apparent mortality of
hummingbirds in eastern North Carolina during the persistent cold in early
January.

I doubt that feeders keep hummers from going south in fall, at least to any
significant extent.

Every winter, especially in early winter, birders find many individuals of
many species of landbirds that did not go south to "where they should be".
These are birds of varying sensitivities to cold or to lack of food due to
cold. Most are insectivorous; they do not use feeders. They include
warblers and many other species. Many of these birds will not survive the
winter, especially if there are periods of severe cold and/or icy weather.
Perhaps the most unfortunate of these birds that did not "go far enough
south" are those that really screw up, and actually go northward in the
fall, ending up in places like Nova Scotia and Newfoundland, where they are
certainly doomed. A large percentage, probably a majority, of these "lost"
birds are immatures. (I wonder if immature males predominate--am thinking
of the human analogy!)

I looked back through old Chat magazines recently to check on my memory.
Hummingbirds, presumably almost all Ruby-throateds, were occasionally
spotted in early winter well before there were any feeders being maintained
in winter--in fact, to the best my knowledge, back when very few persons
maintained hummingbird feeders at any season. For instance, in my county of
Carteret there were four reports (at four different sites) of hummers in
early to mid-winter (early December to mid-January) in 1979-1980. Again,
these birds were not here because of any feeders. Some of you old-timers
may remember that particular winter. It was very mild in December and
through most of January (I remember the flowers where I was staying in late
January), but then we went into a deep freeze in February, topped off by a
snowstorm at the beginning of March. During that winter I think that many
hummers could have survived without a feeder through most of January, but
would have been doomed later on.

However, I do think it is likely that we are sustaining a wintering
population of hummingbirds that is occurring somewhat farther north than
where it would survive without feeders. I am not saying that we are keeping
individual birds from migrating south, but that perhaps by keeping birds
with a genetic tendency to not migrate farther south in winter from
perishing, we are allowing such birds to survive and reproduce, thus
contributing to this more northerly wintering population. In this regard, I
think back to the first wintering birds at feeders in my area (I think it
was in the late 1980's/early 1990's). We were arguing a lot about what
species they were, in part because we had heard so much from Gulf Coast
birders about how our birds could NOT be Ruby-throateds, but also because
those first wintering birds at feeders were almost exclusively immature
birds--we did not see any adult males which would have helped us identify
them more confidently.

If we are maintaining a more northerly wintering population, is that good,
bad, or neutral? Might there be an intense winter storm some year that will
eventually wipe out most of this wintering population (such as the
"blizzard" of December 1989--I can't believe a single hummer could have
survived that weather here). Or will such events become increasingly less
likely in a warming world (although some research suggests that a warming
Arctic leads to wilder kinks in the jet stream, resulting in some invasions
of very cold air into the eastern Unitied States, like the recent cold).
Anyway, the cold in early January was statistically a very rare event,
especially in terms of its persistence. As I've said earlier on this
listserv (I think I have anyway), I have had wintering hummers in my yard
since 2002-2003. I think the only hummers that have died here during this
period other than the ones this year were two (of eight birds) in January
2003. The conditions then were actually more severe than this winter, but
they did not last as long.

Another comment I have is if one thinks that hummingbird feeders keep
hummers from going south, shouldn't we also be concerned about plants that
flower in winter, most of which are exotic planted (and invasive) species
like sasanqua and elaeagnus, although there are native ones like coral
honeysuckle. I have seen hummers in winter that were associated with thick
growths of elaeagnus that were nowhere close to any feeders. And how about
those relatively cozy micro-climate situations, many of which are man-made,
although there are some natural ones too. I remember one mid-December day
watching a Ruby-throated that was going after swarms of tiny flying insects
over a relatively warm south-facing slope (on a dredge island). And there
was a coral honeysuckle plant with numerous flowers at that same site.

Something I do feel very strongly about: If someone has been feeding
hummingbirds in winter such that the birds are really tied to that
particular yard, I think they have an obligation to keep those feeders
maintained throughout the winter, but especially in really cold, severe
weather. When conditions get really bad, and the birds are really stressed,
they will not have the luxury of making a long flight. I feel that this is
especially the case for people like me, who do not live close to any other
feeders.

And, a final comment: I remember when I was in college being told (by my
major professor) that beginning about 1950 feeders had kept Baltimore
Orioles from migrating south to Central America. Do we think that is really
true? Or is more likely that orioles that did not migrate south to "where
they should have gone" found feeders, which enhanced their survival. I
think the latter is more likely.

Susan Campbell and Ann Maddock may want to make some comments about my
thoughts, especially in regard to the degree that Ruby-throateds might
survive in witner without feeders. I do think that for my area--Carteret
County--hummers would not be able to survive throughout an average winter,
although they might (and obviously have) survive well into a typical
December, and into January of some years.

John Fussell
Morehead City, NC

 
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